Great horned owls primarily communicate by hooting. This establishes territorial dominance and is also used to search for mates. Their distinctive territorial call, "hoo-hoo hoooo hoo-hoo," can be heard from miles away. They screech loudly when attacking prey. Sometimes recordings of hooting sounds are used to determine population densities. Great horned owls use their vision to locate prey and navigate in the darkness, even through dense forests. They have binocular vision, which allows excellent frontal vision but weaker peripheral vision. They can lose their vision from trauma, pathogenic infection, and possibly from inherited genetic disorders.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Great horned owls are one of the most widespread and successful bird species in the United States. They are not threatened or endangered.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Great horned owls may prey upon poultry raised as livestock.
Great horned owls feed on species at many different trophic levels, including many rodent and insect species that are considered pests by humans. They can adapt to ecosystems inhabited by humans and can act as a control to an overabundance of these pests.
Positive Impacts: controls pest population
Reproduction of great horned owls is heavily dependent upon prey availability. For example, populations increase when numbers of its primary prey the snowshoe hare, Lepus americanus, were highest. When snowshoe hare abundance lowered, so did the number of great horned owls.
Great horned owls are at risk for parasitism, though it is not always lethal. They can be afflicted with avian malaria if bitten by an infected blackfly. They change nest locations depending on blackfly activity; in the summer when blackflies are active, they roost on or near the ground. In the winter, when fly activity is lower, they will return to the canopy areas.
Commensal/Parasitic Species:
Great horned owls are carnivores that primarily eat terrestrial vertebrates. They have a variable diet that depends on the availability of prey. In late successional areas, they feed on lagomorphs and voles. In the southwestern U.S. where great horned owls are smaller, they often feed on smaller prey like juvenile rabbits and small rodents or insects. In fields and deserts, their primary diet is likely to consist of rodents and insects. In a habitat surrounded by or adjacent to water, they are capable of hunting fish, amphibians, crustaceans, and reptiles. When hunting, they perch and search for prey, then swoop down and catch it while airborne if necessary.
Animal Foods: birds; mammals; amphibians; reptiles; fish; insects; aquatic crustaceans
Primary Diet: carnivore (Eats terrestrial vertebrates)
Great horned owls are native to a large geographic range that covers most of North America and extends south into Central and South America. Their latitudinal range is from 68 degrees north latitude (around the northern tip of Alaska) to 54 degrees south latitude (near the southern tip of Brazil).
Biogeographic Regions: nearctic (Native ); neotropical (Native )
Great horned owls are well suited for many habitats and environments. They live at a variety of elevations, from sea level up to 3352.8 meters. Great horned owls are most commonly found in interspersed areas of woodland and open fields. Their habitats include grasslands, deserts, swamps, marshes, mangroves, and both rural and urban human settlements.
Range elevation: 0 to 3352.8 m.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: tundra ; taiga ; desert or dune ; savanna or grassland ; chaparral ; forest ; rainforest ; scrub forest ; mountains
Aquatic Biomes: coastal
Wetlands: marsh ; swamp ; bog
Other Habitat Features: urban ; suburban ; agricultural ; riparian ; estuarine
The average life expectancy of great horned owls is 13 years. The record for the longest life in the wild is 28 years old. In captivity, the average lifespan is 20 years and the longest recorded lifespan is 35 years. Human activities such as habitat degradation are also expected to affect their lifespan.
Average lifespan
Status: wild: 28 years.
Average lifespan
Status: captivity: 35 years.
Average lifespan
Status: wild: 13 years.
Average lifespan
Status: captivity: 20 years.
Average lifespan
Status: wild: 333 months.
Like similar owl species, great horned owls have a rounded facial structure and forward-facing eyes which allow for binocular vision. They have distinctive horn-like feather tufts on the tops of their heads. The tufts are usually darker than the rest of the head, improving camouflage. They have a distinctive white spot on their throat. Their underbellies are white with brown and black 'bars' distributed throughout. They are white or tan colored around a black bill. Their back is darker in color, featuring a mottled blacks and browns. Their eyes are different shades of yellow in color.
The size and of great horned owls varies by their geographic location and their sex. They exhibit reverse sexual dimorphism, where females are slightly larger than males. Females average about 1.7 kg, while males average 1.3 kg. Evidence suggests this dimorphism is not influenced by environmental factors. This conclusion comes from the observation that great horned owls generally do not migrate sufficient distances to cross-breed with subspecies which may differ in size. In northern latitudes, they tend to have larger core bodies and a longer wingspan. Their overall length is 45.7 to 63.5 cm and their wingspan is 127 to 152.4 cm. This is consistent with Bergmann's rule, which states that in broadly-distributed genuses, larger individuals of species are found in northern latitudes, while smaller individuals are found in southern latitudes. Variations in color also exist depending on geographic location. For example, Bubo virginianus saturatus, a woodland-inhabiting subspecies of great horned owl, may have darker, browner coloration. Bubo virginianus elachistus, which lives in desert habitats in Baja California, may have a lighter, grayer coloration.
Average mass: 1.3 (males) 1.7 (females) kg.
Range length: 45.7 to 63.5 cm.
Range wingspan: 127 to 152.4 cm.
Other Physical Features: endothermic ; bilateral symmetry ; polymorphic
Sexual Dimorphism: female larger
Average mass: 1450 g.
Average basal metabolic rate: 5.2442 W.
Great horned owls are at the top of many food chains and are not preyed upon by other species. However, territorial disputes between members of the same species can be fatal. Sometimes crows (Corvus brachyrhynchos) or raccoons (Procyon lotor) eat their eggs, however.
Known Predators:
Great horned owls are monogamous, forming a mating pair that raise the young. Breeding pairs are territorial, excluding other breeding pairs from their territory to ensure access to prey. However, they may only display territorial behavior in areas close to their nest and do not completely protect their territory. Mates find one another through 'hooting' rituals, which increase in intensity as the mating season approaches. Males hoot throughout the year, but females only hoot during mating season.
Mating System: monogamous
Great horned owls inhabit nests abandoned by squirrels or other birds, including other great horned owls. Their brood sizes depend on food availability and geographic location. Smaller broods are more common in years with lower prey abundance. On the eastern seaboard, broods than 2 are considered rare. In central and western North America, however, a brood size of 3 to 4 is not uncommon. They have 1 to 6 eggs per season which hatch in 30 to 37 days. Great horned owl chicks fledge in 6 to 9 days and achieve independence at 5 to 10 weeks. They achieve sexual maturity in 1 to 3 years. Like other birds with a large geographic distribution, great horned owls tend to nest later in the year relative to the increase in latitude of their location.
The mating ritual of great horned owls is described 'violent nodding and bowing', followed by a quieter 'billing and cooing' stage that signifies the completion of copulation.
Breeding interval: Great horned owls breed on a seasonal basis.
Breeding season: Breeding occurs between the months of November and April.
Range eggs per season: 1 to 6.
Range time to hatching: 30 to 37 days.
Range fledging age: 6 to 9 weeks.
Range time to independence: 5 to 10 weeks.
Range age at sexual or reproductive maturity (female): 1 to 3 years.
Range age at sexual or reproductive maturity (male): 1 to 3 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous
Average eggs per season: 3.
Males and females alternate roosting and hunting during the time they are nesting. Males do the majority of the hunting while females spend their time protecting the brood. When prey is scarce, females are more likely to leave the nest unattended to search for additional food, especially if the clutch size is larger than average. The location of their nest varies. In late successional areas, they are more likely to roost in elevated areas (up to 100 feet). In prairies and early successional areas, they set up nests in bushes, cliff nooks, and even on the ground.
Parental Investment: altricial ; male parental care ; female parental care ; pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
A large (18-25 inches) owl, the Great Horned Owl is most easily identified by its brown body, flat disk-shaped face with large yellow eyes, and large brown “ear” tufts. This species may be distinguished from the similarly-sized Barred Owl (Strix varia) by that species’ lack of ear tufts and brown eyes. Male and female Great Horned Owls are similar to one another at all seasons. The Great Horned Owl is the most widely distributed owl species in the Americas. This species occurs from Alaska and northern Canada south to Central America, and South American populations occur from Venezuela south to southern Argentina and Chile. All populations of Barred Owl are non-migratory. Great Horned Owls may be found in a number of woodland habitat types across this species’ wide range, from cold evergreen woodland in the far north and south to humid tropical forest near the equator. Within these habitats, Great Horned Owls prefer open areas along woodland edges, frequently venturing outside the forest into nearby fields and meadows to hunt. Great Horned Owls eat small animals, including rodents, rabbits and hares, and small to medium-sized birds. Great Horned Owls use their excellent hearing to locate prey on the ground in order to fly down and capture it with its talons. Also, like most owls, this species hunts primarily at night, making it difficult to observe. Great Horned Owls are most visible roosting high in trees during the day, and may best be located while producing this species’ characteristic hooting calls between dawn and dusk.
The Great Horned Owl is the most common and widespread large owl found in the Americas. Its range spans much of the New World from the Arctic tundra to the tip of South America. A variety of subspecies are recognized based on regional differences in size and color. Throughout its range, this owl has adapted to many different habitats and climates from temperate forests, tropical rainforests, and deserts to agricultural fields and urban parks, but it is generally more common in open, fragmented areas than in dense primary forests.
The Great Horned Owl is characterized by prominent ear tufts or "horns" from which it derives its name. It has large yellow eyes surrounded by a tawny facial disk. A conspicuous, narrow, white patch is often visible on the throat. The adult plumage is mottled and varies in color from reddish brown to light or dark grey. The underside usually has fine dark bars on a lighter background. These owls also have large feet that are feathered down to the strong, heavy talons. Immature owls resemble the adults, but their plumage color is generally lighter or more reddish. Their ear tufts are smaller and the white throat patch is not yet distinctive.
A large (18-25 inches) owl, the Great Horned Owl is most easily identified by its brown body, flat disk-shaped face with large yellow eyes, and large brown “ear” tufts. This species may be distinguished from the similarly-sized Barred Owl (Strix varia) by that species’ lack of ear tufts and brown eyes. Male and female Great Horned Owls are similar to one another at all seasons. The Great Horned Owl is the most widely distributed owl species in the Americas. This species occurs from Alaska and northern Canada south to Central America, and South American populations occur from Venezuela south to southern Argentina and Chile. All populations of Barred Owl are non-migratory. Great Horned Owls may be found in a number of woodland habitat types across this species’ wide range, from cold evergreen woodland in the far north and south to humid tropical forest near the equator. Within these habitats, Great Horned Owls prefer open areas along woodland edges, frequently venturing outside the forest into nearby fields and meadows to hunt. Great Horned Owls eat small animals, including rodents, rabbits and hares, and small to medium-sized birds. Great Horned Owls use their excellent hearing to locate prey on the ground in order to fly down and capture it with its talons. Also, like most owls, this species hunts primarily at night, making it difficult to observe. Great Horned Owls are most visible roosting high in trees during the day, and may best be located while producing this species’ characteristic hooting calls between dawn and dusk.
Distribucion General: Se encuentra desde Alaska y el norte de Canadá hasta la Tierra del Fuego.
El búho cornudu, búho real[2] o búho americanu[3] (Bubo virginianus) ye una especie d'ave estrixiforme de la familia de los búhos (Strigidae). Ye nocherniega, de plumaxe rayáu. Ye dacuando tamién llamáu búho real americanu.
Habita nel continente americanu, dende Tierra del Fueu hasta'l norte d'Estaos Xuníos. Ye consideráu como la especie de búho más grande d'América.
El so pesu varia ente los 650 g y hasta 1 kg na mayoría de les subespecies. Añera en oquedades de tueros, y puede poner de 2 a 3 güevos. Aliméntase de pequeños mamíferos, reptiles ya inclusive peces. Reproducióse en cautiverio. Utilizóse y síguese utilizando para cetrería.
El búho cornudu, búho real o búho americanu (Bubo virginianus) ye una especie d'ave estrixiforme de la familia de los búhos (Strigidae). Ye nocherniega, de plumaxe rayáu. Ye dacuando tamién llamáu búho real americanu.
An toud-Virginia a zo un evn-preizh, Bubo virginianus an anv skiantel anezhañ.
a vo kavet e Wikimedia Commons.
An toud-Virginia a zo un evn-preizh, Bubo virginianus an anv skiantel anezhañ.
El duc americà,[1] duc reial[2] o duc banyut (Bubo virginianus) és una espècie d'au estrigiforme de la família dels Strigidae. És nocturn, de plomatge ratllat.
Habita al continent americà, des de Terra del Foc fins al nord dels Estats Units. És considerat com a l'espècie de mussol més gran d'Amèrica.
El seu pes varia entre els 650 g i fins a 1 kg en la majoria de les subespècies. Nia en forats buits de troncs, i pot pondre de 2 a 3 ous. S'alimenta de petits mamífers, rèptils i fins i tot peixos. S'ha reproduït en captiveri. S'ha fet servir i es continua utilitzant per a falconeria.
La subespècie B. v. magellanicus[3] (tucúquere o mussol magallànic) ara es classifica com a l'espècie B. magellanicus.[4]
El duc americà, duc reial o duc banyut (Bubo virginianus) és una espècie d'au estrigiforme de la família dels Strigidae. És nocturn, de plomatge ratllat.
Aderyn a rhywogaeth o adar yw Tylluan gorniog fawr (sy'n enw benywaidd; enw lluosog: tylluanod corniog mawr) a adnabyddir hefyd gyda'i enw gwyddonol Bubo virginianus; yr enw Saesneg arno yw Great horned owl. Mae'n perthyn i deulu'r Tylluanod (Lladin: Strigidae) sydd yn urdd y Strigiformes.[1]
Talfyrir yr enw Lladin yn aml yn B. virginianus, sef enw'r rhywogaeth.[2] Mae'r rhywogaeth hon i'w chanfod yng Ngogledd America.
Mae'r tylluan gorniog fawr yn perthyn i deulu'r Tylluanod (Lladin: Strigidae). Dyma rai o aelodau eraill y teulu:
Rhestr Wicidata:
rhywogaeth enw tacson delwedd Cordylluan Glaucidium passerinum Cordylluan Bolifia Glaucidium bolivianum Cordylluan Brasil Glaucidium brasilianum Cordylluan Ciwba Glaucidium siju Cordylluan dorchog Glaucidium brodiei Cordylluan fannog Glaucidium perlatum Cordylluan frongoch Glaucidium tephronotum Cordylluan Hardy Glaucidium hardyi Cordylluan resog Asia Glaucidium cuculoides Cordylluan y goedwig Glaucidium radiatum Cordylluan y Gogledd Glaucidium gnoma Cordylluan yr Andes Glaucidium jardiniiAderyn a rhywogaeth o adar yw Tylluan gorniog fawr (sy'n enw benywaidd; enw lluosog: tylluanod corniog mawr) a adnabyddir hefyd gyda'i enw gwyddonol Bubo virginianus; yr enw Saesneg arno yw Great horned owl. Mae'n perthyn i deulu'r Tylluanod (Lladin: Strigidae) sydd yn urdd y Strigiformes.
Talfyrir yr enw Lladin yn aml yn B. virginianus, sef enw'r rhywogaeth. Mae'r rhywogaeth hon i'w chanfod yng Ngogledd America.
Výr virginský (Bubo virginianus) je statný a velký pták, jeden z mnoha zástupců rodu Bubo. Obývá severní, střední i Jižní Ameriku. Je to velice přizpůsobivý pták s velkým rozsahem rozšíření, ačkoli není v Americe tak rozšířený, jako sova pálená.
Většinu času tráví výr virginský na stromech v jehličnatých, listnatých i ve smíšených lesích, tropických deštných lesích, v prériích, pampách, hornatých oblastech, subarktických tundrách, pouštích, u skalnatých pobřeží a v některých městských oblastech. Ačkoli je jeho výskyt méně obvyklý ve více extrémních oblastech (tj. „srdce“ pouští, příliš husté deštné lesy, vysoké oblasti v arktických tundrách), obývá většinu lokalit v Americe.
Výr virginský dosahuje 46 až 68 cm na výšku, rozpětí křídel 101 až 153 cm a hmotnosti zhruba 1400 g. Obecně jsou největší sovy nejblíže u polárních oblastí a nejmenší sovy poblíž rovníku. Samice jsou o něco větší než samci. Dospělé sovy mají velké ušní chvostky, rudohnědou tvář a bílou skvrnu na hrdle. Vrchní část těla je kropenatá, spodek těla tvoří žlutohnědé svislé vlnkování. Ušní „chvostky“ tvoří pouze pera a nijak nesouvisí se sluchovým ústrojím. Mají skvělý sluch, který jim umožňuje nalézt přesné umístění jejich kořisti.
Výr virginský na svou kořist číhá na vysokých stromech. Potrava tohoto výra je velice různorodá, ale žere převážně malé až střední savce, např. krysy, veverky, myši, krtky, skunky, rejsky, netopýry, lasice, ale také ptáky, hmyz, korýše, obojživelníky, plazy nebo ryby. Na vybraných území se stávají jeho důležitou součástí potravy i zajíci nebo králíci.
Dospělci vydávají čtyřslabičné, někdy pětislabičné „ho-ho-hoo hoo hoo“, mláďata většinou vydávají syčivé a prskavé zvuky.
Období páření se liší spolu s areálem rozšíření, může začínat už v lednu a únoru. Páry většinou využívají opuštěných hnízd od jiných druhů ptáků, někdy hnízdí v dutinách či na skalních útesech. Samice snese nejčastěji bílá 2-3 vejce, je-li dostatek potravy tak i 6, oba rodiče na nich sedí zhruba 35 dní.
Rozlišujeme u něj několik poddruhů:
Výr virginský (Bubo virginianus) je statný a velký pták, jeden z mnoha zástupců rodu Bubo. Obývá severní, střední i Jižní Ameriku. Je to velice přizpůsobivý pták s velkým rozsahem rozšíření, ačkoli není v Americe tak rozšířený, jako sova pálená.
Der Virginia-Uhu (Bubo virginianus) ist eine Vogelart aus der Gattung der Uhus (Bubo), die zur Familie der Eigentlichen Eulen (Strigidae) und zur Ordnung der Eulen (Strigiformes) gehört. Die Art ist in mehreren Unterarten über große Teile von Nord-, Mittel und Südamerika verbreitet. Der nah verwandte, in angrenzenden Regionen Südamerikas lebende Magellan-Uhu (Bubo magellanicus) wurde lange Zeit ebenfalls als eine Unterart des Virginia-Uhus angesehen.
Der Virginia-Uhu ist mit einer Länge von 46 bis 63 cm und Spannweite zwischen 91 und 151 cm eine der größten Eulenarten des amerikanischen Kontinents. Die Weibchen sind 10 bis 20 Prozent größer als die Männchen. Das Gewicht des Virginia-Uhus liegt bei 0,9 bis 1,8 kg. Die Gefiederfarbe variiert von grau bis rot-braun. Auf der Unterseite verlaufen dunkle Streifen längs seines Körpers sowie ein weißes Band auf der Brust. Der Bauch ist etwas heller als der Rücken. Er hat lange Ohren oder „Hörner“, die seinen englischen Namen Great Horned Owl erklären. Wie bei allen Uhus haben diese Federohren allerdings keine Bedeutung für den Gehörsinn. Die großen Augen sind gelblich orangefarben. Die Füße sind bis zu den Krallen befiedert.
Der Gesang des Männchens ist ein tiefes, weit klingendes bu-bubú booh booh, das in Intervallen von mehreren Sekunden wiederholt wird. Das Weibchen singt ähnlich, hat aber einen anderen Rhythmus und ruft bu-bububú booh.[1]
Der Virginia-Uhu bevorzugt offene Landschaften mit Bäumen oder Waldrändern, aber auch bewaldete Gebirgsregionen bis 4000 m Höhe und sogar Parks.
Der Virginia-Uhu ernährt sich überwiegend von Säugetieren, die bis zum Dreifachen seines eigenen Körpergewichts wiegen können, darunter Ratten, Mäuse, Kaninchen und Skunks, aber auch von Vögeln wie Tauben, Enten und anderen Eulen. Die Jagd findet dabei meist im Gleitflug statt, die Beute wird im Sturzflug mit angezogenen Flügeln geschlagen. Fische, Amphibien und kleine Alligatoren jagt er zum Teil auch auf dem Boden gehend und sogar im Wasser.
In Gefangenschaft können Virginia-Uhus über 30 Jahre alt werden, wild lebende Tiere leben selten mehr als 15 Jahre lang.
Während der Paarungszeit im Januar und Februar lassen Männchen und Weibchen den typischen Ruf hu-hu huuh hu-hu hören. Die Stimme des Männchens ist tiefer als die des Weibchens.
Wie die meisten Uhus bauen Virginia-Uhus keine Nester, sondern benutzen gerne verlassene Greifvogelnester. Ihre Eier (zwei bis vier bei einem Gelege) werden innerhalb von 28 bis 35 Tagen ausgebrütet, wobei ausschließlich die Weibchen brüten. Die Jungtiere verlassen nach 6 bis 7 Wochen kletternd das Nest, nach 9 bis 10 Wochen sind die Jungtiere flügge.
Die Elternpaare teilen sich oft über viele Jahre dasselbe Territorium, leben allerdings außerhalb der Brutzeit solitär.
Der Virginia-Uhu kommt in großen Teilen Nordamerikas außerhalb der Arktis sowie in einigen Regionen Mittel- und Südamerikas vor. Im südlichen Südamerika grenzt sein Verbreitungsgebiet an das des eng mit ihm verwandten Magellan-Uhus, der die Anden-Region bis Feuerland besiedelt. Die Art gilt laut IUCN als derzeit nicht gefährdet.[2]
Es werden folgende Unterarten unterschieden:
Der Virginia-Uhu (Bubo virginianus) ist eine Vogelart aus der Gattung der Uhus (Bubo), die zur Familie der Eigentlichen Eulen (Strigidae) und zur Ordnung der Eulen (Strigiformes) gehört. Die Art ist in mehreren Unterarten über große Teile von Nord-, Mittel und Südamerika verbreitet. Der nah verwandte, in angrenzenden Regionen Südamerikas lebende Magellan-Uhu (Bubo magellanicus) wurde lange Zeit ebenfalls als eine Unterart des Virginia-Uhus angesehen.
பெரிய கொம்பு ஆந்தை (great horned owl) என்பது ஆந்தை வகைகளில் ஒரு பறவையாகும். இவ்வாந்தை பெரிய அளவுள்ளது. கள்ளப்பருந்தைவிடக் கனமான பறவையாகும்.
பெரிய கொம்பு ஆந்தை கருந்தவிட்டு நிறமுடையது. மேனியில் கருங்கோடுகள் நீள்வட்டமாக காணப்படும். இரு கொம்புகள் போல கரு நிற இறகுகள் காதுக்கு மேலே உயர்ந்து இருக்கும்.
பெரிய கொம்பு ஆந்தை (great horned owl) என்பது ஆந்தை வகைகளில் ஒரு பறவையாகும். இவ்வாந்தை பெரிய அளவுள்ளது. கள்ளப்பருந்தைவிடக் கனமான பறவையாகும்.
The great horned owl (Bubo virginianus), also known as the tiger owl (originally derived from early naturalists' description as the "winged tiger" or "tiger of the air"),[3] or the hoot owl,[4] is a large owl native to the Americas. It is an extremely adaptable bird with a vast range and is the most widely distributed true owl in the Americas.[5] Its primary diet is rabbits and hares, rats and mice, and voles, although it freely hunts any animal it can overtake, including rodents and other small mammals, larger mid-sized mammals, birds, reptiles, amphibians, and invertebrates. In ornithological study, the great horned owl is often compared to the Eurasian eagle-owl (Bubo bubo), a closely related species, which despite the latter's notably larger size, occupies the same ecological niche in Eurasia, and the red-tailed hawk (Buteo jamaicensis), with which it often shares similar habitat, prey, and nesting habits by day, thus is something of a diurnal ecological equivalent.[6] The great horned owl is one of the earliest nesting birds in North America, often laying eggs weeks or even months before other raptorial birds.[7]
The great horned owl was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the other owls in the genus Strix and coined the binomial name Strix virginia.[8] Gmelin based his description on that of English naturalist George Edwards who had described and illustrated the great horned owl in 1747 in the second volume of his A Natural History of Uncommon Birds. Edwards had seen a live specimen from Virginia at the house of the Earl of Burlington in Chiswick. Edwards also owned a preserved specimen, and another specimen formed part of the Leverian collection.[9] The great horned owl is now placed in the genus Bubo that was introduced in 1805 by André Duméril.[10][11]
The great horned owl represents one of the one or two radiations of the genus across the Bering land bridge to the Americas. Whereas the Magellanic horned owl clearly divided once the owl had spread through the Americas, the consensus seems to be that the snowy owl and the great horned owl divided back in Eurasia and the snowy then spread back over the Arctic through northernmost North America separately from the radiation of the horned owl.[12][13] The great horned and Eurasian eagle-owls may in fact be conspecifics, based on similarities in life history, geographic distribution, and appearance.[6] In one case, a zoo-kept male great horned owl and female Eurasian eagle-owl produced an apparently healthy hybrid.[14] Genetic testing indicates that the snowy owl, not the Eurasian eagle-owl, is the most closely related living species.[12] Pleistocene era fossils have been found of Bubo owls in North America, which may either be distinct species or paleosubspecies, from as far east as Georgia, but predominantly in the Rocky Mountains and to the west of them.[15][16] Almost all fossils indicate these owls were larger than modern great horned owls.[17][18]
A large number of subspecies, more than 20 altogether, have been named. However, many of these are not true subspecies and only examples of individual or clinal variation. Subspecies differences are mainly in color and size and generally follow Gloger's and Bergmann's rules:[15] The most conservative treatments of great horned owl subspecies may describe as few as 10,[12] although an intermediate number is typical in most writings.[15]
Fifteen subspecies are currently recognised:[11]
The great horned owl is generally colored for camouflage.[7] The underparts of the species are usually light with some brown horizontal barring; the upper parts and upper wings are generally a mottled brown usually bearing heavy, complex, darker markings. All subspecies are darkly barred to some extent along the sides, as well.
A variable-sized white patch is seen on the throat. The white throat may continue as a streak running down the middle of the breast even when the birds are not displaying, which in particularly pale individuals can widen at the belly into a large white area. South American great horned owls typically have a smaller white throat patch, often unseen unless actively displaying, and rarely display the white area on the chest.[6] Individual and regional variations in overall color occur, with birds from the subarctic showing a washed-out, light-buff color, while those from the Pacific Coast of North America, Central America, and much of South America can be a dark brownish color overlaid with blackish blotching. The skin of the feet and legs, though almost entirely obscured by feathers, is black. Even tropical great horned owls have feathered legs and feet. The feathers on the feet of the great horned owl are the second-longest known in any owl (after the snowy owl).[6] The bill is dark gunmetal-gray, as are the talons.[12]
All great horned owls have a facial disc. This can be reddish, brown, or gray in color (depending on geographical and racial variation) and is demarked by a dark rim culminating in bold, blackish side brackets.[19] This species' "horns" are tufts of feathers, called plumicorns. The purpose of plumicorns is not fully understood, but the hypothesis that they serve as a visual cue in territorial and sociosexual interactions with other owls is generally accepted.[6]
The great horned owl is the heaviest extant owl in Central and South America and is the second-heaviest owl in North America, after the closely related, but very different-looking snowy owl.[7][12] It is heavily built, with a barrel-shaped body, a large head, and broad wings.[12] Its size can vary considerably across its range, with populations in interior Alaska and Ontario being largest and populations in California and Texas being smallest, though those from the Yucatán Peninsula and Baja California appear to be even smaller.[20][21] Adult great horned owls range in length from 43 to 64 cm (17 to 25 in), with an average of 55 cm (22 in), and possess a wingspan of 91 to 153 cm (3 ft 0 in to 5 ft 0 in), with an average of 122 cm (48 in). Females are somewhat larger than males.[15][22] Mean body weight is 1,608 g (3.545 lb) for females and 1,224 g (2.698 lb) for males.[23][24] Depending on subspecies, maximum weight can reach 2,503 g (5.518 lb).[25]
The wing chord length is 297–400 mm (11.7–15.7 in).[26] The wing loading, the measured wing area compared to weight, is high, meaning the wings are relatively small in surface area for the bird's weight; the species' wing loading has been described as proportionately the highest among raptors.[19][27] The tail, being relatively short as is typical of most owls, is 175 to 252 mm (6.9 to 9.9 in) long. Like other owl species, the great horned owl is capable of “silent flight”, which is the way owls fly while making almost no discernable noise, despite their large size. This is made possible thanks to three main components of the owl's wing structure. The leading edge of their feathers have serrations that help to disrupt the turbulence generated by wing flapping, then the softer feathers help deaden the sound, and finally the trailing fringe of the feathers that works to finish cutting the sounds made by flight. The structure of the great horned owl wing also allows it to fly at a very low speeds for the size of the species, as slow as 2 miles per hour when they are gliding on breezes.[28]
The legs, feet, and talons are large and powerful. Tarsal length is 54–80 mm (2.1–3.1 in).[12] The average foot span of a fully spread foot, from talon to talon, is around 20 cm (7.9 in), as compared to 8 cm (3.1 in) in long-eared owls, 13 to 15 cm (5.1 to 5.9 in) in barn owls, and 18 cm (7.1 in) in the great grey owl.[6][29] Great horned owls can apply at least 300 lb/in2 of crushing power in their talons, a pressure considerably greater than the human hand is capable of exerting. In some big females, the gripping power of the great horned owl may be comparable to much larger raptor species such as the golden eagle.[30]
The hard, inflexible bill of the great horned owl is 3.3–5.2 cm (1.3–2.0 in) long, although the culmen, the exposed bill portion as measured along the top of the beak, is only 2.1 to 3.3 cm (0.83 to 1.30 in).[31]
The outer ear openings, which are concealed by feathers on the sides of the head, are relatively smaller than those of the Eurasian eagle owl, being 2.3 cm (0.91 in) in vertical axis, with the left ear slightly larger than the right.[32] Like most exclusively (or near exclusively) nocturnal species, the great horned owl has asymmetrical ear holes that allow for the triangulation of sounds when hunting in the dark. The different-height holes, while still close together, are differentiated enough that the owl is able to use the timing and direction of the sound waves hitting each hole to precisely locate prey even if the prey is located under cover such as snow. The disc-like shape of their faces also helps to direct the sounds they hear toward their ears. While the true nature/purpose of the ear tufts that are present on the great horned owl is unknown, researchers agree that the tufts do not play any role in the hearing ability of the owl. It is estimated that their hearing is up to ten times that of a human being.[33]
The great horned owl's eyes, just slightly smaller than the eyes of a human being, are large even for an owl and rank proportionately among the largest eyes of all terrestrial vertebrates.[34] The great horned owl has cylindrical eyes which creates more distance from the lens of the eye to the retina, which allows it to act more like a telephoto lens for farther distance sight compared to that possible from round eyes.[35] They are visually highly adapted for nocturnal hunting and provide a wide, almost completely binocular field of view, a large corneal surface and a predominantly rod retina.[36] The great horned owl's eye contains both rods and cones like most species that see in color, but the vision of a great horned owl closely resembles that of many other nocturnal species. The peak wavelengths that are observed by the cones is 555 nm and the research suggests that the great horned owl has relatively weak color vision, especially compared to other bird species. Despite (or perhaps as a result of) the poorer sense of color vision, the owl manages to have excellent night vision.[37] Instead of turning its eyes, an owl must turn its whole head, and the great horned owl can rotate its neck 270°. The iris is yellow, except in the amber-eyed South American great horned owl (B. v. nacurutu).
The great horned owl's song is normally a low-pitched but loud ho-ho-hoo hoo hoo (or also transcribed as bu-bubu booh, who-hoo-ho-oo or who-ho-o-o, whoo-hoo-o-o, whoo) and can last for four or five syllables. The call is resonant and has warranted descriptions as varied as "solemn" and "terrifying".[6][7] The female's call is higher and rises in pitch at the end of the call. Female vocalizations are higher in pitch because of a smaller syrinx in the larger sex.[38] Calling seems to peak after rather than before midnight.[39][40] Usually, territorial hooting decreases in February or March at the onset of egg laying.[41] On occasion, this species exhibits "an indescribable assemblage of hoots, chuckles, screeches, and squawks, given so rapidly and disconnectedly that the effect is both startling and amusing".[42] Descriptions of some of these odd sounds including a growling krrooo-ooo note pair, a laughing whar, whah, wha-a-a-a-ah, a high-pitched ank, ank, ank; a weak, soft erk, erk, a cat-like meee-owwwwww, a hawk-like note of ke-yah, ke-yah, and a nighthawk-like peent. These vocalizations may be variously uttered when the birds are disturbed and angered at the nest (frequently preceding an attack on an interloping human or other animal), represent the vocal development of young owls, or are given during courtship and during territorial disputes with other owls.[7][15][43] Young owls still in the care of their parents make loud, persistent hissing or loud, piercing screeching sounds that are often confused with the calls of the barn owl.[12]
Common/eastern great horned owl (Bubo virginianus virginianus)
South American great horned owl (Bubo virginianus nacurutu)
Northern/sub-Arctic great horned owl (Bubo virginianus subarcticus)
California great horned owl (Bubo virginianus pacificus)
Coastal great horned owl (Bubo virginianus saturatus)
North Andean great horned owl (Bubo virginianus nigrescens)
Desert great horned owl (Bubo virginianus pallescens)
Yucatán great horned owl (Bubo virginianus mayensis)
Baja California great horned owl (Bubo virginianus elachistus)
Northeastern great horned owl (Bubo virginianus heterocnemis)
Rocky Mountains great horned owl (Bubo virginianus pinorum)
The combination of the species' bulk, prominent ear tufts and barred plumage distinguishes it through much of the range, but it may be easily confused with the lesser or Magellanic horned owl (B. magellanicus), which may overlap in range.[12] The Magellanic horned owl was once considered a subspecies of the great horned, but is now almost universally considered a distinct species, as is supported by genetic materials, with the great horned being the paraspecies.[12][19] Overall coloration is similar, but the Magellanic is markedly smaller with smaller feet and a smaller head, with finer, but more numerous brownish bars on the underside, rather than the blotchy, irregular barring typical of great horned owls.[12] Other eagle-owls may superficially be somewhat similar, but the species is generically allopatric with the exception of wintering snowy owls. More tropical species with ear tufts, the stygian owl (A. stygius) and striped owl (A. clamator), are much smaller.[12] Other large owls lack ear tufts.[6]
The breeding habitat of the great horned owl extends high into the subarctic of North America, where they are found up to the northwestern and southern Mackenzie Mountains, Keewatin, Ontario, northern Manitoba, Fort Chimo in Ungava, Okak, Newfoundland and Labrador, Anticosti Island and Prince Edward Island. They are distributed throughout most of North America and very spottily in Central America and then down into South America south to upland regions of Argentina, Bolivia and Peru, before they give way to the Magellanic horned owl, which thence ranges all the way to Tierra del Fuego, the southern tip of the continent. It is absent or rare from southern Guatemala, El Salvador, Nicaragua, and Costa Rica to Panama (where only two records) in Central America and the mangrove forests of northwestern South America. The species is also absent from the West Indies, the Haida Gwaii and almost all off-shore islands in the Americas, its ability to colonize islands apparently being considerably less than those of barn owls and short-eared owls.[6][45][47][56][57] Since the division into two species, the great horned owl is the second most widely distributed owl in the Americas, just after the barn owl.[12]
The great horned owl is among the world's most adaptable owls or even bird species in terms of habitat. The great horned owl can take up residence in trees that border all manner of deciduous, coniferous, and mixed forests, tropical rainforests, pampas, prairie, mountainous areas, deserts, subarctic tundra, rocky coasts, mangrove swamp forests, and some urban areas.[12] It is less common in the more extreme areas of the Americas. In the Mojave and Sonora Deserts, they are absent from the heart of the deserts and are only found on the vegetated or rocky fringes. Even in North America, they are rare in landscapes including more than 70% old-growth forest, such as the aspen forest of the Rockies.[15][58] They have only been recorded a handful of times in true rainforests such as the Amazon rainforest.[6] In the Appalachian Mountains, they appear to use old-growth forest[59] but in Arkansas are actually often found near temporary agricultural openings in the midst of large areas of woodland.[60] Similarly in south-central Pennsylvania, the owls use cropland and pasture more than deciduous and total forest cover, indicating preference for fragmented landscapes.[61] In prairies, grasslands and deserts, they can successfully live year round as long as there are rocky canyons, steep gullies and/or wooded coulees with shade-giving trees to provide them shelter and nesting sites.[6][62]
In mountainous areas of North America, they are usually absent above the tree line, but great horned owls can be found up to 2,100 m (6,900 ft) in California and 3,300 m (10,800 ft) in the Rockies.[6][63] In the Andean Mountains, on the other hand, they have adapted to being a true montane species, often found at least 3,300 m (10,800 ft) above sea level and are regularly recorded in treeless Puna grassland zones at 4,100 to 4,500 m (13,500 to 14,800 ft) in Ecuador and Peru.[64] They are generally rare in non-tidal wetland habitat,[65] and are replaced in the high Arctic tundra by snowy owls.[12] They prefer areas where open habitats, which they often hunt in, and woods, where they tend to roost and nest, are juxtaposed.[40][66][67] Thus lightly populated rural regions can be ideal. This species can occasionally be found in urban or suburban areas. However, they seem to prefer areas with less human activity and are most likely to be found in park-like settings in such developed areas, unlike eastern and western screech owls (Megascops asio & M. kennicottii) which may regularly occur in busy suburban settings. All mated great horned owls are permanent residents of their territories, but unmated and younger birds move freely in search of company and a territory, and leave regions with little food in winter.[12]
In most aspects of their behavior, great horned owls are typical of owls and most birds of prey. From experimentally raising young owls in captivity, Paul L. Errington felt that they were a bird of "essentially low intelligence" that could only hunt when partially wild and instinctually driven by hunger to hunt whatever they first encounter. He showed captive birds that were provided strips of meat from hatching, rather than having to hunt or to simulate hunting to obtain food, had no capacity to hunt.[68] On the contrary, William J. Baerg compared behaviorally his captive-raised great horned owls to parrots, which are famously intelligent birds, although not as often playful "it knows its keeper and usually accepts whatever he wishes to do with a good deal of tolerance".[69]
Arthur C. Bent also noted the variability in temperaments of great horned owls to their handlers, some generally pleasant, though most are eventually aggressive.[7] Most captive specimens, once mature, seem to resent attempts at contact and are often given to attacking their keepers. They will only follow cues when conditioned from an early age but rarely with the same level of success seen in some diurnal birds of prey trained for falconry or entertainment, although this does not necessarily correlate with intelligence as posited by Errington.[68][69] Carl D. Marti also disagrees with Errington's assessments, noting that their prey selection is not as "completely random as Errington suggested"; while "Great Horned Owls appeared to select their mammalian prey in general relation to the prey populations. Cottontails, however, appeared to be selected as prey out of relation to their population status".[29]
Like most owls, the great horned owl makes great use of secrecy and stealth. Due to its natural-colored plumage, it is well camouflaged both while active at night and while roosting during the day. During the daytime it roosts usually in large trees (including snags & large hollows but usually thick branches) but may occasionally be in crevices or small caves in rocks or in dense shrubbery. Pine and other coniferous trees may be preferred where available since they are particularly dense and provide cover throughout the year. Typically, males have a favorite roosting site not far from the nest, sometimes used over successive years.[4] While roosting, great horned owls may rest in the "tall-thin" position, where they sit as erect and hold themselves as slim as is possible. The kind of posture is well known as a further method of camouflage for other owls, like long-eared owls or great grey owls, especially if humans or other potential mammalian carnivores approach them. The Eurasian eagle owl rarely, if ever, assumes the tall-thin position.[70]
Outside of the nesting season, great horned owls may roost wherever their foraging path ends at dawn.[43] Generally great horned owls are active at night, although in some areas they may be active in the late afternoon or early morning. At dusk, the owl utters a few calls before flying to a more open sing-post, i.e. large bare branch or large rocks to deliver song. Normally several perches are used to mark occupied territory or to attract a female.[12] Despite its camouflage and cryptic locations, this species can still sometimes be spotted on its daytime roosts, especially by American crows (Corvus brachyrhynchos). Since owls are, next to red-tailed hawks, perhaps the main predator of crows and their young, crows sometimes congregate from considerable distances to mob owls and caw angrily at them for hours on end. When the owls try to fly off to avoid this harassment, they are often followed by the corvids.[71]
Typically, great horned owls are highly sedentary, often capable of utilizing a single territory throughout their mature lives.[72] Although some species such as snowy owls, northern saw-whet owls, long-eared and short-eared owls are true migrants, most North American owls are not migratory and will generally show fidelity to a single territory year around.[6] In great horned owls, mated pairs occupy territories year-round and long-term. Territories are established and maintained through hooting, with highest activity before egg-laying and second peak in autumn when juveniles disperse, and can range from an average of 16 km2 (6.2 sq mi) in Yukon to an average of 2.1 km2 (0.81 sq mi) in Wyoming.[23][43]
Most territorial defense is performed by males, but females frequently assist their partners in hooting contests with neighbors or intruders, even during incubation.[15] On occasion, although territory borders may be successfully maintained via vocalizations alone without even seeing the competing owl, such confrontations may turn physical, with various levels of threats distinguished. The highest threat level involves the spreading of wings, bill-clapping, hissing, higher-pitched screams of longer duration, with general body poised to strike with its feet at intruder. If the intruder continues to press the confrontation, the defending owl will "hop" forward and strike it with feet, attempting to grasp and rake with claws.[15]
Territoriality appears to place a limit on the number of breeding pairs in a given area. Individuals prevented from establishing a territory live a silent existence as "floaters". Radio-telemetry revealed that such floaters concentrate along boundaries of established territories. At Kluane Lake in Yukon, incursions into neighboring territories were observed only twice—by females when a neighboring female had died or emigrated, suggesting that territorial defense may be sex-specific. At least four dead great horned owls in Kluane were apparently killed by others of their own species in territorial conflicts.[43] Owls killed by other horned owls are sometimes cannibalized, although the origin of the killing may have been territorial aggression.[73] Northern populations occasionally irrupt south during times of food shortage,[74] but there is no annual migration even at the northern limits of the great horned owl's range.[43]
Hunting tends to peak between 8:30 pm and midnight and then can resume from 4:30 am to sunrise.[75] Hunting tends to be most prolonged during winter by virtue of prey being more scarce.[76] However, great horned owls can learn to target certain prey during daylight in the afternoon when it is more vulnerable, such as eastern fox squirrels (Sciurus niger) while they're building their leaf nests and chuckawallas (Sauromalus ater) sunning themselves on desert rocks.[77][78] Owls hunt mainly by watching from a snag, pole or other high perch. During hunting forays, they often fly about 50 to 100 m (160 to 330 ft) from perch to perch, stopping to survey for food at each, until they sense a prey item below. From such vantage points, owls dive down to the ground, often with wings folded, to ambush their prey.[12] Effective maximum hunting distance of an owl from an elevated perch is 90 m (300 ft).[41] Due to their short but broad wings, great horned owls are ideally suited for low speed and maneuverability.[27]
Despite reports that they do not hunt on the wing,[79] they also sometimes hunt by flying low over openings on the ground, scanning below for prey activity.[12] Great horned owls can fly at speeds of more than 65 km/h (40 mph) in level flight.[6] Hunting flights are slow, often quartering low above the ground where prey is likely to occur in open country or open woodland. Brief hovering flight (for about 6–18 seconds) has been described, especially in windy areas.[80] On occasion owls may actually walk on the ground in pursuit of small prey or, rarely, inside a chicken coop to prey on the fowl within.[22] Rodents and invertebrates may be caught on foot around the base of bushes, through grassy areas, and near culverts and other human structures in range and farm habitat.[15] The great horned owl is generally a poor walker on the ground; it walks like a starling, with a pronounced side-to-side gait. They have been known to wade into shallow water for aquatic prey, although this has been only rarely reported.[15] Owls can snatch birds and some arboreal mammals directly from tree branches in a glide as well. The stiff feathering of their wings allows owls to produce minimal sound in flight while hunting.[5][12][22]
Almost all prey are killed by crushing with the owl's feet or by incidentally stabbing of the talons, though some may be bitten about the face as well. Prey is swallowed whole when possible. When prey is swallowed whole, owls regurgitate pellets of bone and other non-digestible bits about 6 to 10 hours later, usually in the same location where the prey was consumed.[12] Great horned owl pellets are dark gray or brown in color and very large, 7.6 to 10.2 cm (3.0 to 4.0 in) long and 3.8 cm (1.5 in) thick, and have been known to contain skulls up to 3 cm (1.2 in) in width inside them.[22] However, not all prey can be swallowed at once, and owls will also fly with prey to a perch and tear off pieces with their bill. Most dietary studies focus on pellets found under perches and around nests, since they provide a more complete picture of the diversity of prey consumed, but prey remains outside of pellets may provide clues to prey excluded from the pellets and a combination of both is recommended.[6][81][82]
Many large prey items are dismembered. Great horned owls may behead large prey before taking it to its nest or eating perch. The legs may also be removed, as may (in some bird prey) the wings. The great horned owl will also crush the bones of its prey to make it more compact for carrying.[83] On occasion, the owls may return to the kill site to continue eating if the prey is too heavy to fly with after dismemberment.[7] Many owls will accrue a cache of prey, especially those who are nesting. Caches must be at a safe location, usually the crotch of a tall tree. In northern regions, where large prey is prevalent, an owl may let uneaten food freeze and then thaw it out later using its own body heat.[19] Hunting success seems to require fairly open understory, and experimental testing of microhabitat proved that open areas provided more hunting success on five species of rodent, with cloudy nights and denser bush foliage both decreasing success.[84]
Prey can vary greatly based on opportunity. According to one author, "Almost any living creature that walks, crawls, flies, or swims, except the large mammals, is the great horned owl's legitimate prey".[30] In fact, the great horned owl has the most diverse prey profile of any raptor in the Americas.[6] Over 500 species have been identified as great horned owl prey, with dozens more identified only to genus or general type (especially numerous invertebrates) and presumably several more unknown from their relatively little-studied populations in the Neotropics. Mammals (more than 200 species) and birds (nearly 300 species) make up the majority of their diet.[6][81] Their diet in North America is made up of 87.6% mammals, 6.1% birds, 1.6% reptiles and amphibians with the remaining 4.7% being made up by insects, other assorted invertebrates and fish.[6]
Estimated mass of individual prey for the owls has ranged from as little as 0.4 g (0.014 oz) to as much as 6.8 kg (15 lb)[85][86] Most prey is in the range of 4 g (0.14 oz) (shrews) to 2,300 g (5.1 lb) (jackrabbits).[85][87] A single owl requires about 50 to 100 g (1.8 to 3.5 oz) of food per day and can subsist on a large kill over several days.[88] Despite the great diversity of prey taken by these predators, in most of the continental United States from the East to the Midwest as well as Canada and Alaska, great horned owls largely live off just a handful of prey species: three species of lagomorph: the eastern cottontail (Sylvilagus floridanus), the snowshoe hare (Lepus americanus) and the black-tailed jackrabbit (Lepus californicus); two species of New World mice: the white-footed mouse and the North American deermouse (Peromyscus leucopus & maniculatus); approximately three species of vole: the meadow, prairie and woodland voles (Microtus pennsylvanicus, ochrogaster & pinetorum); and one introduced pest, the brown rat.[15][81][85]
Small rodents form the great majority of great horned owl prey by number. Weighing a mere 14 to 31.5 g (0.49 to 1.11 oz) and 20 to 58 g (0.71 to 2.05 oz) on average, the nine species of New World mice in Peromyscus and eight species voles in Microtus recorded in the diet would appear to be overly small to be as important as they are to a predatory bird of this size. The prominence of these genera is undoubtedly due to the abundance of both genera in the wooded edge habitats frequented by great horned owls. It is estimated that a family of owls with two offspring would need to take about a half dozen (voles) to a dozen (mice) of these rodents every night to satisfy their dietary requirements but apparently the accessibility and abundance of these foods is irresistible as their numeric dominance is indisputable.[23][81] By winter in areas that hold heavy snow, Peromyscus mice often come to outnumber the voles in the diet since the mice tend to travel over the surface of the snow while the voles make tunnels underneath the snow.[23][6][81] In fact, a healthy family of great horned owls can decimate a colony of field rats, thus potentially performing a key role in controlling a highly destructive pest.[81] Great horned owls living in the timbered fringes of garbage or refuse dumps may subsist mostly on rats.[19]
In the Rockies, California, the Southwestern United States and northern Mexico, the diversity of this species' diet rises, in sync with the diversity of rodents. Especially important, from Colorado to Washington state is the northern pocket gopher (Thomomys talpoides), although assorted other pocket gophers (Geomys, Cratogeomys, Zygogeomys, Pappogeomys and other Thomomys ssp.) are readily taken. While the northern weighs from 90 to 120 g (3.2 to 4.2 oz), other pocket gophers hunted average from 95 to 545 g (0.209 to 1.202 lb) in mass. From Washington to Baja California a very important food is the pocket mice, primarily the Great Basin pocket mouse (Perognathus parvus). While the Great Basin species is a relative giant at 22 g (0.78 oz), other hunted pocket mice (which may include both Perognathus and Chaetodipus ssp.) can average nearly as light as 8 g (0.28 oz). In East Texas, the 159 g (5.6 oz) hispid cotton rat (Sigmodon hispidus) is the most commonly recorded prey species.[89] The same species constituted 75% by number of a small sampling in Oklahoma.[90] In semi-desert and other arid habitats, kangaroo rats become increasingly important prey, ten species have been reported in the diet but most prominently the Ord's and Merriam's kangaroo rats (Dipodomys ordii & merriami), both being widespread, numerous and relatively diminutive (at 42 and 48 g (1.5 and 1.7 oz)). Eight known larger species of kangaroo rats, including the giant kangaroo rat (Dipodomys ingens) averaging at 152 g (5.4 oz), are also taken.[91][92][93]
The squirrels, including ground squirrels, marmots (Marmota), prairie dogs (Cynomys), chipmunks and tree squirrels, are diurnal and so are largely unavailable to great horned owls as prey. Occasionally though, one will be caught from their leaf nest, nest hole or burrow entrance first thing in the morning or in the late afternoon and approximately 35 species have been successfully predated by these owls. In general larger sized than other rodent families, the species hunting range from the 62 g (2.2 oz) gray-collared chipmunk (Tamias cinereicollis) to the 5,775 g (12.732 lb) hoary marmot (Marmota caligata); thus, squirrels can be provide a very fulfilling meal.[7][15][94] An even larger rodent is sometimes attacked as prey by great horned owls, the North American porcupine (Erethizon dorsatum), in which average adults range from 4,500 to 9,000 g (9.9 to 19.8 lb). This has been determined from owls who have porcupine quills imbedded in them, sometimes resulting in death.[7][95] On occasion, they are successful in killing porcupine, even adults as determined by the size of the quills left behind and prey remains at bloodied kill sites.[88][96][97] Other rodents recorded as secondary prey in North America include flying squirrels (Glaucomys ssp.), the golden mouse (Ochrotomys nuttalli), red-backed voles & bog lemmings (Myodes & Synaptomys ssp.), the muskrat (Ondatra zibethicus), the northern grasshopper mouse (Onychomys leucogaster), the northern pygmy mouse (Baiomys taylori) and jumping mice (Zapus & Napaeozapus ssp.).[7][15]
Although generally no match for rodents in sheer quantity of individuals, in terms of prey biomass, the most significant prey of North American great horned owls are hares and rabbits. About a dozen lagomorphs species are known to be hunted by the owl, from the relatively tiny 420 g (0.93 lb) pygmy rabbit to several hares weighing more than 2,000 g (4.4 lb). Two hare species, the black-tailed jackrabbit and snowshoe hare, are so important to the owls as a food source that the local owl populations sharply rise and fall in sync with the hares' cyclical population trends. With adult weights of 800 to 1,900 g (1.8 to 4.2 lb) in adult cottontails, 900 to 2,000 g (2.0 to 4.4 lb) in snowshoe hares and 1,400 to 2,700 g (3.1 to 6.0 lb) in black-tailed jackrabbits, these species are overall the largest regular prey for this species.[6]
In Utah, where great horned owls are dependent on the jackrabbits, average brood size rose from 2 at jackrabbit population lows to 3.3 when the jackrabbits were at their peak. At the peak of population cycle, jackrabbits accounted for 90.2% and desert cottontails (Sylvilagus audubonii) for another 8.7% of prey biomass.[75][98] In the short-grass prairie of Colorado, mountain cottontail (Sylvilagus nuttallii) and black-tailed jackrabbits predominated in October to December, making up 42.9% by number (and nearly all the biomass), thence dropping to 9.3% by number in April, while voles rose to 32.2% peak in May, down to a minimum of 10.2% by number in June.[6] Further north in Colorado, in the absence of jackrabbits, the mountain cottontails falls to third place by number (12.9%) behind the northern pocket gopher (36.5%) and prairie vole (24.7%) but still dominates the biomass, making up about half.[99] In central Utah, the lagomorphs (black-tailed jackrabbit/desert cottontail) and Ord's kangaroo rat each made up 39% of the food by number, respectively.[75] The mountain cottontail dominates the biomass of prey in the Sierran foothills of California, making up 61.1% of the biomass, although are numerically secondary to desert woodrat.[91] Remarkably, in the Morley Nelson Snake River Birds of Prey National Conservation Area of Idaho, individual rodents (1159 counted) were more than 10 times more numerous than lagomorphs (114 counted) by quantity and yet the jackrabbit and mountain cottontail still made up approximately half of the biomass.[100] The dependence on lagomorphs also extends into Mexico, as in Baja California about a quarter of identified prey was black-tailed jackrabbit and either desert or the larger Mexican cottontail (Sylvilagus cunicularius).[101]
In the northern boreal forest, great horned owls are even more dependent on the snowshoe hare. At the peak of the 10 year hare cycle, snowshoe hares were by far the largest component of both summer and winter diets (77–81% and 90–99%, respectively, in Alberta; 83–86% and 75–98%, respectively, in Yukon). At the lowest point of the hare's cycle, summer diets consisted of only 0–16% snowshoe hare in Alberta and 12.7% in Yukon. When hares were scarce, great horned owls in these regions fed mostly on large rodents, mice and voles, grouse and ducks. Because fewer of these alternative prey species are available in boreal forest during winter, owls had to emigrate or suffer high mortalities if they stayed.[102][103] In Alberta, the local population of great horned owls can increase threefold from hare population lows to peaks.[104] The dependency on the snowshoe hare by the great horned owl extends into Alaska as well.[105]
Other mammals are taken readily as well. From both the tropics and the United States, several species of opossum may be taken, down to the size of the tiny dwarf fat-tailed mouse opossum (Thylamys velutinus). In Brazil, white-eared opossum (Didelphis albiventris) were found in 12% of pellets, but all specimens appeared to be juveniles each weighing about 1,000 g (2.2 lb).[106] Quite differently, in Pennsylvania, Virginia opossum (Didelphis virginianus) made up 6% by number of prey but due to their large size (approximately 2,500 g (5.5 lb)) and that all specimens were adults, they occupied the highest percentage of biomass of any species in a wide study from that state.[107] At least eight species of shrews are taken by opportunity and make up the smallest mammalian prey taken by great horned owls, as specimens of least shrew (Cryptotis parva) or masked shrew (Sorex cinereus) have had an estimated weight of only 2 g (0.071 oz).[85]
One of the more regularly taken shrews, though, is the larger 19.5 g (0.69 oz) northern short-tailed shrew (Blarina brevicauda), which was represented in more than 2% of pellets in the Upper Midwest.[81] Moles, of at least four or five species, are also widely but lightly reported as prey.[81][85] Remnants of armadillo, presumably nine-banded armadillo (Dasypus novemcinctus), have been found around owl nests in the south.[7] 11 species of bat are known to be hunted by great horned owls.[6][108][109][110] One pellet in Texas was found to be composed entirely of Mexican free-tailed bats (Tadarida brasiliensis).[111] Smaller species of mammalian carnivore, such as ringtail (Bassariscus astutus), American mink (Neogale vison), black-footed ferret (Mustela nigripes) and various other small mustelids (Mustela ssp.), are sometimes taken as prey.[7][15][112][113] Prey in the form of canids, like foxes or coyotes (Canis latrans) are often juveniles presumably snatched from the mouths of dens by night.[7][15][114][115][116] Kit and swift foxes of up to adult size may taken.[88][117][118]
Surprisingly, at least two cases of a great horned owl preying on an adult raccoon (Procyon lotor) have been reported.[119][120] One instance of an owl taking a bobcat (Lynx rufus) as prey was also reportedly observed.[88] In one case, a great horned owl was the likely killer of an adult female fisher (Martes pennanti), though young ones are typically taken.[121][122] Occasionally, domestic carnivores are also prey. A few cases of young or small dogs (Canis lupus familiaris)[123][124] and several of juvenile and adult cats (Felis silvestris catus)[125][126][127] being killed by great horned owls have been reported.[7][116][128] The most infamous predatory association amongst relatively larger carnivores is that with skunks. Due to their poor sense of smell, great horned owls are the only predators to routinely attack these bold mammals with impunity. All six skunk species found in North America are reported as prey, including adult striped skunks (Mephitis mephitis), which can be three times as heavy as the attacking owl.[7][85][129] In one single nest, the remains of 57 striped skunks were found.[130] Due to the proclivity of skunk predation, great horned owls nests frequently smell strongly of skunk and occasionally stink so powerfully of skunk that they leave the smell at kill sites or on prey remains.[15][131]
After mammals, birds rank as the next most important general prey group. Birds are usually considerably secondary in the diet but outnumber the mammals in the diet by diversity, as more than 250 species have been killed in North America alone. Statistically, the most significant avian prey seems to be galliforms, of which they are known to have preyed on 23 species, basically consisting of all of the native species found in the United States.[7][15] In the Upper Midwest, the ring-necked pheasant (Phasianus colchicus) and northern bobwhite (Colinus virginianus) were the fifth and sixth (out of 124 identified species) most significant prey species in 4838 pellets.[81] Errington characterized the predatory pressure exerted on bobwhites by great horned owls as "light but continuous pressure", which may be considered characteristic of the species' hunting of all galliforms.[132]
Usually coveys of quail are partially protected by spending the night roosting communally in dense thickets but should a hunting owl be able to track down the communal roost, losses can be fairly heavy until the roost relocates.[23] Similarly, owls may track down sleeping grouse, which also roost in vegetation but more openly than quail. Some grouse, such as greater prairie chicken (Tympanuchus cupido), sharp-tailed grouse (Tympanuchus phasianellus) and greater sage-grouse (Centrocercus urophasianus), may also been vulnerable to great horned owls while displaying conspicuously in openings on a lek first thing in the morning.[133] In the boreal forest, especially in years where the snowshoe hare experiences population decreases, great horned owls prey fairly heavily (approximately 25% of biomass) on ruffed grouse (Bonasa umbellus) and spruce grouse (Falcipennis canadensis), enough so in the earlier bird to possibly contribute to population reductions.[102][134] Larger species of galliform are not immune to predation either. On Protection Island in Washington state, introduced common peafowl (Pavo cristatus) are an important prey item.[135] The wild turkey (Meleagris gallopavo), 4 to 8 kg (8.8 to 17.6 lb) on average between the sexes, is probably the largest bird the great horned owl hunts in which they kill adults. Both full-grown wild turkeys[136] and adult domestic turkeys[7] have been hunted and killed. Under normal circumstances, domestic chicken (Gallus gallus domesticus) will be ignored in favor of wild prey. On occasion, individual owls, especially inexperienced juveniles, will become habitual fowl killers. These errant owls mainly hunt chickens, though will also take domestic guineafowl, turkeys and anything else available.[81] In general, chickens kept in locked cages with enclosed tops overnight are safe from great horned owls; not so chickens left free range or in open enclosures.[7]
While galliforms are widely reported, the few cases where great horned owls locally turn to birds as the primary food source over mammals, these may often be local responses to the abundance of breeding water birds or concentrations of roosting water birds, since they tend to roost in relatively open spots. They have been known to predate more than 110 different species of assorted water bird.[6] In prairie wetlands of North Dakota, avian prey, primarily represented by ducks and the American coot (Fulica americana) came to represent 65% by number and 83% by biomass of the diet of the local owls, also including secondarily grebes, smaller rails, loons, shorebirds and seabirds, as well as upland-based species like grey partridge (Perdix perdix), sharp-tailed grouse and passerines.[137] 77% of the ducks in that study were juveniles, the largest duck being a male mallard (Anas platyrhnychos) weighing approximately 1,250 g (2.76 lb), but nearly all the coots were adults.[86] On Protection Island, Washington, where they are no native land mammals, rhinoceros auklets (Cerorhinca monocerata), both adults and nestlings, were the most numerous prey, present in 93% of 120 pellets.[135] Species as large as adult Canada geese, snow goose[7][81] and great blue herons[15] have been successfully killed. Medium-sized birds of prey (even other species of owl) are also taken.[138] The nestlings of even larger species like trumpeter swans (Cygnus buccinator),[139] American white pelicans (Pelecanus eryhtrorhynchos),[140] brown pelicans (Pelecanus occidentalis)[141] and sandhill cranes (Grus canadensis)[142] have also been killed by these owls.
Other assorted birds are taken seemingly at random opportunity. The predatory effect of this species on other raptorial birds, which is often considerable, is explored in the following section. In Brazil, it was found in a small study that birds overall outnumbered mammals in pellets, although most were not determined to species and the ones that were shown a tremendously diverse assemblage of birds with no obvious dietary preference.[106] Although not usually numerically significant, 86 species of passerine have been taken by great horned owls. Members from most North American families are known as prey, although among smaller types such as chickadees, warblers, sparrows, cardinals, wrens and most tyrant flycatchers only a few species from each have been recorded. Nonetheless, an occasionally unlucky migrant or local breeder is sometimes snatched.[6][7][81] Fledgling songbirds are regularly taken in spring and summer.[88] The smallest avian prey known for great horned owls are the 5.8 g (0.20 oz) blue-grey gnatcatcher (Polioptila caerulea) and the 6.2 g (0.22 oz) ruby-crowned kinglet (Regulus calendula).[81] Somewhat larger bodied families are more prominent, i.e. the corvids (14 species) and icterids (14 species) and, secondarily, the kingbirds (Tyrannus ssp.), thrushes, mimids and European starling (Sturnus vulgaris).[6][7][81] This is likely due to the fact that the larger passerines usually roost in relatively open spots and have larger, more conspicuous nests. Crows and ravens tend to be grabbed off of their communal roosts by night.[15]
The great horned owl rarely misses an opportunity to hunt reptiles and amphibians. However, lizards are largely unavailable as prey due to their typically diurnal periods of activity.[15] However, some snakes are partially or largely nocturnal, and more than a dozen species are hunted in North America. Snakes hunted range from small, innocuous garter snakes (Thamnophis ssp.) and night snakes (Hypsiglena torquata) to venomous species like cottonmouths (Agkistrodon piscivorus) and prairie rattlesnakes (Crotalus virdis) and formidable, large species like common king snakes (Lampropeltis getula) and black rat snakes (Pantherophis obsoletus), which in mature specimens can rival the owl in mass and sheer predatory power.[7] The capture of the hatchlings of very large reptiles such as loggerhead turtles (Caretta caretta) and American alligators (Alligator mississippiensis) by great horned owls has been reported, in both cases likely when the baby reptiles are attempting to make their way to the security of water.[7][143] On rare occasion, salamanders, frogs and toads are reported as prey. On rare occasions, fish are taken including goldfish (Carassius auratus), bluegill (Lepomis macrochirus), bullheads (Ameiurus ssp.), other catfish, suckers, sunfish, eels and dace and chub.[7][88]
Many types of invertebrates are recorded as prey. These include mainly insects, but also crayfish, crabs, centipedes, spiders, scorpions and worms.[137] The occasionally invertebrate prey taken largely consists of common, large insects such as various beetles, crickets, grasshoppers, water bugs and katydids, some of which the great horned owl has even reportedly caught via "hawking", i.e. swooping at on the wing.[7][15][144] In some cases, the content of insects in great horned owl pellets may actually be due to the owls eating other birds which have freshly eaten insects in their own stomachs.[81] It is commonly believed that routine insectivory in great horned owls is mainly restricted to inexperienced young owls too unskilled to graduate to larger prey yet. It is clearly inefficient for owls of this size to attempt to raise young on a diet of foods as small as insects.[29] Although rare, carrion-feeding has been recorded in great horned owls, especially ones wintering in Canada and other northern areas during harsh weather.[145] Road kills are sometimes opportunistically eaten. A case of an owl scavenging a white-tailed deer (Odocoileus virginianus) carcass, ultimately tearing off the deer's leg, was captured on a motion capture video camera set out to film wildlife.[146]
Studies comparing the diets of rural and urban great horned owls have identified that the most abundant rodent prey in their environment fulfils the majority of their diet.[147][148][149][150] A study of food niche overlap between closely nested barn and great horned owls living in rural north-eastern Oregon identified voles as by far the most common prey.[148] In southwestern British Columbia, Townsend's voles were the most common prey species, while consumption of rats increased as the nesting location became more urban and rats replaced voles as the most abundant and stable food source.[147] A similar focus on rats was found in populations in urban parks in Seattle.[151] Although a stable and highly abundant food source, a diet consisting of primarily rats can be harmful to urban great horned owls due to bioaccumulation of rodenticides.[152]
Due to their very broad dietary habits, the great horned owls share their prey with many other predators, including avian, mammalian and reptilian ones. Almost every study comparing the diets of North American owls illustrates the considerable overlap in the dietary selection of these species, as all species, besides the primarily insectivorous varieties, rely on many of the same small rodent species for most of their diet, extending from the small northern saw-whet owl and eastern screech owl to the great horned and great grey owls.[29][85]
In a long-term study of a block of Michigan, all nine species of accipitrid, falcon and owl that stayed to breed there were found to be primarily dependent on the same two rodent genera, the meadow vole and the two common Peromyscus species.[23] In the Great Basin, the owls share black-tailed jackrabbit and desert cottontail as the primary prey with golden eagles, red-tailed hawks and ferruginous hawks (Buteo regalis); all four species had diets with more than 90% of the biomass is made up of those lagomorphs. Of these, the great horned owl and golden eagle were able to nest most closely to one another because they had the most strongly dissimilar periods of activity.[62][98] In California, when compared to the local red-tailed hawks and western diamondback rattlesnakes (Crotalus atrox), the diets were most similar in that by number about 15-20% of all three species' diets depended on cottontails, but the largest portion was made up of ground squirrels in the hawk and the rattlesnake and desert woodrats and other assorted rodents in the great horned owl.[91] In the boreal forests, the great horned owl's prolificacy as a snowshoe hare hunter places it second only to the Canada lynx (Lynx canadensis) among all predators. Although locally dependent on the hares as their main food, northern goshawks (Accipiter gentilis), red-tailed hawks and golden eagles apparently do not have as large of an impact on the hares, nor do mammalian carnivore generalists that also kill many hares, like the fisher, bobcat, wolverine (Gulo gulo), coyote and larger varieties (i.e. wolves (Canis lupus), cougars (Puma concolor) and bears (Ursus ssp.)).[43][74][104][153]
The relationship between great horned owls and other raptorial birds in its range is usually decidedly one-sided. While certain species, such as the red-tailed hawk and northern goshawk, might be seen as potential competition for the owls, most others seem to be regarded merely as prey by great horned owls. The great horned owl is both the most prolific and diverse predator in America of other birds of prey, with other accomplished raptor-hunters such as the goshawk and the golden eagle being more restricted in range, habitat and number in North America and thus having a more minor impact. All studies have found raptors are a small portion of this owl's diet but predation can be seriously detrimental for such prey, as raptors tend to be territorial and sparsely distributed as a rule and thus can be effectively decimated by a small number of losses.[6][85] In the gray hawk (Buteo plagiatus), for example, in a study of one breeding block of Arizona, the owls were observed to visit nests nightly until all the nestlings were gone.[154]
Raptorial birds in general tend to have large, conspicuous nests which may make them easier for a hunting owl to locate. The great horned owl gains an advantage by nesting earlier than any other raptor in its range (indeed any bird), as it is able to exploit the other raptors as food while in a more vulnerable state as their own nestlings have become well developed.[23] On average, great horned owls begin nesting about three weeks before red-tailed hawks begin to build nests, although some raptors may locally breed as much as two months after the owls.[15][155]
More so than diurnal varieties of raptor, fairly significant numbers of owls are hunted, as all species are to some extent nocturnal and thus their corresponding activity can attract the horned owl's unwanted attention. The extent of predation on other owls depends on the habitat preferences of the other species. Eastern and western screech owls may be most vulnerable since they prefer similar wooded edge habitat. In a block of Wisconsin, great horned owls were responsible for the failure of 78% of eastern screech owl's nests.[23] Long-eared owls and, to a lesser extent, barn owls tend to hunt in open, sparsely treed habitats more so than great horned owls, but since they may return to wooded spots for nesting purposes, they may be more vulnerable there. The long-eared owl and barn owls are often compared to the great horned owl as these medium-sized species often occur in abutting habitats and often hunt primarily the same vole and mice species, although the alternate prey of the great horned tends to be much larger, including the smaller owls themselves.[26][79][156] In a pair of studies from Colorado, the average weight of prey for long-eared owls was 28 to 30 g (0.99 to 1.06 oz), 46 to 57.1 g (1.62 to 2.01 oz) for barn owl and 177 to 220 g (6.2 to 7.8 oz) for the great horned owl.[29][99]
Both young and adult great grey owls, despite their superficially superior size, are apparently hunted with impunity by great horned owls. In the boreal forests, both the northern hawk owl and great grey owl appear to be in greater danger of great horned owl predation in years where the snowshoe hare have low populations.[157][158] Great horned owls were the leading cause of mortality in juvenile spotted owls (30% of losses) and juvenile great grey owls (65% of losses).[157][159] Less is known about relations with the snowy owl, which may compete with great horned owls for food while invading south for the winter. Anecdotally, both snowy and great horned owls have rarely been reported to dominate or even kill one another depending on the size and disposition of the individual owls, although the snowy's preference for more open areas again acts as something of a buffer. The snowy may be the one North American owl too formidable for the great horned owl to consider as prey.[13]
Whereas owls of any age are freely attacked by great horned owls whether nesting or not, when it comes to diurnal raptors, great horned owls are mainly a danger around the nest. They often hunt diurnal raptors when they come across their often relatively conspicuous active platform nests during hunting forays in spring and summer, taking numbers of both nestlings and brooding adults.[15] Again, like owls, diurnal raptors are attacked depending on the relative similarity of their habitat preferences to the owl. Cooper's hawks (Accipiter cooperii) and red-tailed hawks tend to be most vulnerable, as they prefer the same wooded edges frequented by great horned owls. Other diurnal raptors may be attracted to more enclosed wooded areas, such as sharp-shinned hawks (Accipiter striatus) or zone-tailed hawks (Buteo albonotatus), or more open plain and meadow areas, such as Northern harriers (Circus hudsonius) and ferruginous hawks, but this is almost never a total insurance against predation as all of these are recorded prey.[81][160][161][162]
In a study of red-shouldered hawk (Buteo lineatus) and broad-winged hawk (Buteo brachyurus) breeding in New York, despite their nesting in deeper woods than those that host these owls, the main cause of nest failure was great horned owl predation.[131] Similarly, the great horned owl was the primary cause of nesting failure for both desert-dwelling Harris's hawks (Parabuteo unicinctus) and forest-dwelling northern goshawk in Arizona (39% and 40% of failures, respectively), wetland-inhabiting osprey (Pandion haliaetus) in Delaware (21% of failures) and peregrine falcons (Falco peregrinus) in the Western United States (27% of failures).[163][164][165][166] The fact that many of the nests great horned owls use are constructed by accipitrids may lead to localized conflicts, almost always to the detriment of the hawks rather than the owls. While the young of larger diurnal raptors are typically stolen in the night, great horned owls also readily kill large adult raptors both in and out of breeding seasons, including osprey, northern goshawk and rough-legged buzzard.[167][168][169]
Great horned owls are frequently mobbed by other birds. Most accipitrids will readily mob them, as will falcons. Hen harriers, northern goshawks, Cooper's hawks, Harris's hawks, red-tailed hawks, Swainson's hawks, ferruginous hawks, red-shouldered hawks, American kestrels, peregrine falcons, prairie falcons (Falco mexicanus) and common ravens (Corvus corax) are among the reported species who have been recorded diving on great horned owls when they discover them.[15][82][170][171] In Arizona and Texas, they may be mobbed by Mexican jays and western scrub jays (Aphelocoma wollweberi & californica) and western and Cassin's kingbirds (Tyrannus verticalis & vociferans).[172][173] In addition, there are several documented incidences of American crows mobbing a great horned owl, in groups of dozens or even hundreds of crows.[7] In response to mobbing, if the owl flies it alights to the nearest secluded spot. If an owl alights on ground or on exposed branch or ledge, it may respond to swooping and stooping flights of corvids and raptors with threat display and raising of its wings.[15]
Great horned owls are some of the earliest-breeding birds in North America, seemingly in part because of the lengthy nightfall at this time of year and additionally the competitive advantage it gives the owl over other raptors. In most of North America, courtship is from October to December and mates are chosen by December to January.[12] This species was once thought to be strictly monogamous, but recent analysis indicates one male may mate with two females simultaneously, as was discovered for the first time in 2018 in Reno, Nevada.[174] During courtship in late fall or early winter, the male attracts the attention of his mate by hooting emphatically while leaning over (with the tail folded or cocked) and puffing up his white throat to look like a ball.[12] The white throat may serve as a visual stimulus in the low light conditions typical of when this owl courts.[43] He often flies up and down on a perch, while approaching the potential mate. Eventually, he comes to approach the female and tries to rub his bill against hers while repeatedly bowing. If receptive, the female hoots back when the pair meet but is more subdued in both her hoot and display. The male may convince the female by bringing her freshly caught prey, which they will share.[7][12] While males often hoot emphatically for about a month or six weeks towards the end of the year, the period where females also hoot is usually only a week to ten days.[42] Pairs typically breed together year after year and may mate for life, although they associate with each other more loosely when their young become mostly independent.[12] Pairs rekindling their reproductive relationship in the winter may perform a milder courtship to strengthen pair bonds before producing young.[42]
Males select nesting sites and bring the females' attention to them by flying to the nest and then stomping on it.[12] Considering the owls' large size, nests with open access are preferred to those enclosed with surrounding branches. Like all owls, great horned owls do not build their own nest. Great horned owls tend to examine an area for an abandoned nest, generally from larger birds like hawks, and take over the nest for raising their own young.[175] They nest in a wider variety of sites than any other North American bird.[42] Many nests are in cavernous hollows of dead trees or their branches, and especially in southern states in large trees along the edge of old-growth lots.[42] In mountainous or hilly areas, especially in canyons of the Southwest and Rocky Mountains, cliff ledges, small caves, and other sheltered depressions may be used.[42] Owls living in prairie country, in the absence of other animals' nests, riparian tree-hollows or man-made structures, will use boulders, buttes, railroad cuts, low bushes and even the bare ground as nest sites.[42] Ground nests have also been recorded in the midst of tall grasses in Florida and in the midst of brushy spots on desert ground.[6] Even the burrow entrances of American badger and coyote dens have reportedly been used as nests, in spite of the inherent risk of sharing space with such potentially dangerous co-inhabitants.[42] Nesting behavior for the great horned owl appears to be more closely related to prey availability than it does to seasonal conditions. There has been some evidence that if prey availability is low enough then the species may forgo mating entirely for a season. Male and female owls of the species have been observed to help incubate the eggs once they have been laid on a nest.[176]
Most tree nests used by great horned owls are constructed by other animals, often from a height of about 4.5 to 22 m (15 to 72 ft) off the ground. They often take over a nest used by some other large bird, sometimes adding feathers to line the nest but usually not much more. Allegedly there have some cases where the owls have reinforced a nest structure or appeared to have reconstructed a nest, but as a rule no owl species has ever been known to actually build a nest.[42] Great horned owls in the Southwest may also use nests in cacti, built by Harris's hawk and red-tailed hawk, as well as large hollows in cacti.[177] The nests they use are often made by most larger types of acciptrids, from species as small as Cooper's hawks to bald eagle and golden eagle, though perhaps most often those of red-tailed hawks and other buteonines. Secondly in popularity are crow and raven (Corvus ssp.) nests. Even Canada goose, black-crowned night heron (Nycticorax nycticorax) and great blue heron nests have been used, the latter sometimes right in the midst of an active heronry.[178][179] The leaf nests of squirrels are also regularly used but in general great horned owls are partial to stick nests since they provide a much firmer, safer foundation.[15]
The stage at which eggs are laid is variable across North America. In Southern Florida, eggs may be laid as early as late November to as late as early January. In the southeast, from south Texas to Georgia, egg laying may begin from late December to early February. From Southern California to northern Louisiana, egg laying is from early February to late March. The largest swath of egg-laying owls from central California to South Carolina to as far north as Ohio and Massachusetts is from late February to early April. In the Rocky Mountains, Northwestern United States, northern New England and eastern Canada, egg laying is from early March to late April. In the rest of Canada and Alaska, egg laying may be from late March to early May.[42] The latest known date of egg laying was in mid-June in Saskatchewan and the Yukon Territory.[180] In northwestern Utah and north-central Alberta, egg-laying can be 3–4 weeks earlier than usual when food is abundant and weather is favorable.[15] For owls found in more tropical climates, the dates of the breeding season are somewhat undefined.[12] There are usually 2 eggs per clutch, but clutches range in size from 1 to 6 eggs (over 3 is uncommon, over 4 is very rare), depending on environmental conditions.[181][182] The average egg width is 46.5 mm (1.83 in), the average length is 55 mm (2.2 in) and the average weight is 51 g (1.8 oz), although mass could be slightly higher elsewhere because this figure is from Los Angeles County, CA where the owls are relatively small.[183] The incubation period ranges from 28 to 37 days, averaging 33 days.[184] The female alone usually does all the incubation and rarely moves from the nest, while the male owl captures food and brings it to her, with the first nightly food delivery typically occurring soon after dark.[15]
The young weigh 34.7 g (1.22 oz) at birth on average and can gain about 33 g (1.2 oz) a day for the first four weeks of life, with typical weights in the range of 800 or 1,000 g (1.8 or 2.2 lb) by 25–29 days for males and females, respectively.[183][184] When first hatched the young are covered in whitish gray down, with some brownish about the wings. Gradually the soft juvenal downy plumage comes through the down, being typically a cinnamon-buff color, but with variable hues predicting the eventual color of the mature owls. The extent of down gradually diminishes, developing mature-looking plumage by late summer, although many first year birds still have scattered bits of down into autumn. By late autumn, first-year birds look similar to adults but with a slightly warmer, reddish tinge, less well developed ear tufts and a smaller white throat patch.[7] The nestling owls develop mostly in behavior between two weeks and two months of age, in which time they adapt the ability to defend themselves, grasp foods and climb. Vocally, the young are able to exert weak chips while still in the egg, developing into a raspy chirp shortly after hatching. The calls of the young increase rapidly in intensity, pitch and character, some juvenile males mimicking their father's hooting in fall but usually they conclude with various odd gurgling notes. The earliest competent hooting by juvenile owls is not until January.[15][185] Young owls move onto nearby branches at 6 weeks and start to fly about a week later. However, the young are not usually competent fliers until they are about 10 to 12 weeks old.[12] The age at which the young leave the nest is variable based on the abundance of food.[104]
The young birds stay in an area ranging from 13 to 52 ha from the nest into fall, but will usually disperse up to several thousand hectares by the end of fall.[186][187] The offspring have been seen still begging for food in late October (5 months after leaving the nest) and most do not fully leave their parents territory until right before the parents start to reproduce for the next clutch (usually December to January).[188] Birds may not breed for another year or two, and are often vagrants ("floaters") until they establish their own territories.[43] Based on the development of the bursa, great horned owls reach sexual maturity at two years of age.[189]
While urban and rural populations show little difference in productivity, there are differences in nest selection.[190][191] Rural owls use old raptor nests more frequently than urban birds, who utilize crow or squirrel nests. Additionally, urban nesting individuals utilize trees that are taller/wider in diameter and nest much higher compared to rural nesting Great Horned Owls. The reason behind this increased tree height is due to the fact that urban areas have large trees used for ornamentation, shade and shelter. The higher nesting within the taller trees was attributed to human avoidance. Both rural and urban nesting sites were often within range of paved roads, likely a result of the great horned owl’s tendency to hunt along roadways[190]
Studies have shown that nesting in urban areas can influence adult great horned owls to lay eggs earlier than those who nest in rural areas. In Wisconsin, eggs in urban nests hatched a month earlier (January rather than February) than their counterparts in rural areas, probably due to increased protection from wind and cold.[192] Nesting owls at sites in Winnipeg, Manitoba began nesting five to six weeks earlier than those in rural parts of Manitoba, presumably due to experiencing an extremely warm winter by Winnipeg’s standards, as well as benefitting from the local urban heat island.[193]
Great horned owls seem to be the most long-living owl in North America. Among all owls, they may outrank even the larger Eurasian eagle owl in known longevity records from the wild,[6] with almost 29 years being the highest age for an owl recorded in North America.[194] In captivity, the record for the longest lived great horned owl was 50 years.[195] A more typical top lifespan of a great horned owl is approximately 13 years.[19] In general, great horned owls are most vulnerable in the early stages of life, although few species press attacks on the owl's nests due to the ferocious defensive abilities of the parents. Occasionally, nestlings and fledglings will fall from the nest too early to escape or to competently defend themselves and fall prey to foxes, bobcat, coyotes, or wild or feral cats. Occasionally raccoons and American black bears consume eggs and nestlings from tree nests and Virginia opossum may take the rare unguarded egg.[6][15] Crows and ravens have been reported eating eggs and small nestlings. This can normally only happen when owls are driven from the nest by human activity or are forced to leave the nest to forage by low food resources but on occasion huge flocks of crows have been able to displace owls by harassing them endlessly.[7][15] In general, great horned owls rarely engage in siblicide, unlike many other raptorial birds. Siblicide occurred at 9 of 2,711 nests in Saskatchewan.[74] Most cases where young owls are killed and/or consumed by their siblings or parents appear to occur when the nestling is diseased, impaired or starving or is inadvertently crushed.[81] Adults generally have no natural predators, excepting both North American eagles and other owls of their own species.[7]
Occasionally, great horned owls may be killed by their own prey. Although typically able to kill skunks without ill effect, five owls were found blind after getting sprayed in their eyes by skunks.[196] Cases where the quills of porcupines have killed or functionally disabled them have been observed as well.[95] Violent fights have been observed between great horned owls after attempts to capture rat snakes and black racers.[7][197][198] When a peregrine falcon repeatedly attacked a great horned owl near its nest along the Hudson River, it was apparently unable to dispatch the larger raptor despite several powerful strikes.[199] During their initial dispersal in fall, juvenile owls have a high mortality rate, frequently more than 50%.[15] For owls in the Yukon Territory, juvenile survival in the 9 weeks after dispersal has dropped from 80% to 23.2% in a span of three years in response of instability of food supply. In the Yukon, adults on territory had an average annual survival rate of 90.5%.[43] Anemia, caused by Leucocytozoon ziemanni and the drinking of blood by swarming, blood-drinking blackflies (Simulium ssp.), was a leading cause of juvenile mortality in the Yukon.[66]
The great horned owl is not considered a globally threatened species by the IUCN.[1] Including the Magellanic species, there are approximately 5.3 million wild horned owls in the Americas.[19] Most mortality in modern times is human-related, caused by owls flying into man-made objects, including buildings, cars, power lines, or barbed wire.[15] In one study, the leading cause of death for owls was collision with cars, entanglement with wires, flying into buildings and, lastly, electrocution.[200] Among 209 banded nestlings in yet another study, 67% were found dead after independence: 56 were found shot, 41 were trapped, 15 hit by cars, 14 found dead on highways and 14 electrocuted by overhead power lines.[201] Secondary poisoning from pest control efforts is widely reported variously due to anticoagulant rodenticides, strychnine, organophosphates (famphur applied topically to cattle (Bos primigenius taurus)), organochlorines, and PCBs.[202][203][204][205][206][207]
Frequently, the species were denominated a pest due to the perceived threat it posed to domestic fowl and potentially small game. The first genuine nature conservationists, while campaigning against the "Extermination Being Waged Against the Hawks and Owls", continued to advocate the destruction of great horned owls due to their predatory effect on other wildlife.[6] Thus, small bounties were offered in trade for owl bodies. Around the turn of the 20th century, the great horned owl was considered endangered in the state of Michigan because of the large number of poachers who were illegally hunting and collecting it.[208] Hunting and trapping of great horned owls may continue on a small scale but is now illegal in most countries.
Occasionally, these owls may prey on threatened species. Following the devastation to its populations from DDT, the reintroduction of the peregrine falcon to the Mississippi and Hudson Rivers was hampered by great horned owls killing both young and adult peregrines at night.[209] Similarly, as mainly recorded in New England, attempts to reintroduce ospreys, after they were also hit hard by DDT, were affected by heavy owl predation on nestlings, and the owls were also recorded to take a large toll locally on the threatened colonies of roseate terns.[15] Where clear-cutting occurs in old-growth areas of the Pacific Northwest, spotted owls have been badly affected by considerable great horned owl predation.[40][210] While at least the ospreys and peregrines have rebounded admirably nonetheless, bird and mammal species that are much rarer overall sometimes fall prey to great horned owls, many in which even sporadic losses can be devastating. Among the species considered threatened, endangered or critically endangered by the IUCN which are also known to be killed by great horned owls are Townsend's ground squirrels (Urocitellus townsendii),[100] Pacific pocket mice (Perognathus pacificus),[211] giant kangaroo rats,[212] Stephens' kangaroo rat (Dipodomys stephensi),[213] black-footed ferrets,[214] greater and lesser prairie chickens,[215][216] marbled murrelets (Brachyramphus marmoratus),[217] ivory-billed woodpeckers, Florida scrub jays (Aphelocoma coerulescens),[218] pinyon jays,[219] Kirtland's warblers (Setophaga kirtlandii)[220] and rusty blackbirds (Euphagus carolinus).[132] The American Bird Conservancy's "green list" includes birds with considerable population declines (many classed as near threatened by the IUCN) or other immediate threats and/or restricted populations. Altogether, great horned owls hunt 50 different species from that list.[6][221]
Many warrior-based tribes of Native Americans admired the great horned owl for their "strength, courage and beauty".[88] The Pima of the Southwest believed that owls were reincarnations of slain warriors who fly about by night. The Arikara of the Great Plains had mystic owl societies in which initiates were made to adorn a facial mask made of the wing and tail feathers of great horned owls. Some Indian nations regarded the great horned owl as a friendly spirit that could aid in matters of love, such as the Passamaquoddy of Maine, who felt the call of this species was a magical love flute designed to ignite human passions. The Hopi of the Southwest also associated this owl with fertility, albeit of a different kind: they believed the calling of the owls into summer predicted hot weather, which produced good peach crops. During the winter solstice, the Hopi performed a ceremony with great horned owl feathers in hopes of summoning the heat of summer. Tribes in New Mexico were known to use owl wing-feathers to produce arrows which could strike their enemies with a minimum of sound. The Zuni held owl feathers in their mouths hoping to gain some of the silence that owls use in ambushes while striking their own enemies from other tribes. The Iroquois felt the origin of the great horned owl was due to an unformed owl annoying Raweno, the almighty creator, while Raweno created the rabbit, causing Raweno to make the owl "covered with mud" (dark camouflage) and doomed to ceaselessly call "whoo whoo", which he used while harassing Raweno by night because Raweno was active during the day.[88]
The great horned owl is the provincial bird of Alberta.[222]
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: CS1 maint: multiple names: authors list (link) The great horned owl (Bubo virginianus), also known as the tiger owl (originally derived from early naturalists' description as the "winged tiger" or "tiger of the air"), or the hoot owl, is a large owl native to the Americas. It is an extremely adaptable bird with a vast range and is the most widely distributed true owl in the Americas. Its primary diet is rabbits and hares, rats and mice, and voles, although it freely hunts any animal it can overtake, including rodents and other small mammals, larger mid-sized mammals, birds, reptiles, amphibians, and invertebrates. In ornithological study, the great horned owl is often compared to the Eurasian eagle-owl (Bubo bubo), a closely related species, which despite the latter's notably larger size, occupies the same ecological niche in Eurasia, and the red-tailed hawk (Buteo jamaicensis), with which it often shares similar habitat, prey, and nesting habits by day, thus is something of a diurnal ecological equivalent. The great horned owl is one of the earliest nesting birds in North America, often laying eggs weeks or even months before other raptorial birds.
La granda kornostrigo aŭ virginia kornostrigo, Bubo virginianus, estas specio de granda birdo el la ordo de strigoformaj, familio de strigedoj, kun granda plumtufo super ĉiu okulo. Ĝi estas indiĝena de Norda kaj Suda Ameriko. Ĝi estas adaptema birdo kun ampleksa teritorio, kvankam ne tiom disvastigata kiom tiu de la Turstrigo.
La reprodukta vivejo de la granda kornostrigo disvastiĝas tra Nordameriko kaj Sudameriko. Ene de ties biotopo ili povas loĝi ĉe arboj kiuj inkludas deciduajn, koniferajn kaj miksitajn arbarojn, tropikajn pluvarbarojn, pampojn, herbejojn, montajn areojn, dezertojn, subarktan tundron, rokajn marbordojn, mangrovojn kaj kelkajn urbajn areojn. Kvankam mal pli komuna en la plej ekstremaj areoj (ekz., en la centro de dezertoj, plej densaj pluvarbaroj, ktp.) kaj malesta ĉe la alta arkta tundro, ili troviĝas en plej parto de biotopoj.
La granda kornostrigo estas el 46 ĝis 68 cm longa kaj havas enverguron de 101 ĝis 153 cm. Mezaveraĝa granda kornostrigo estas 55 cm longa, havas enverguron de 124 cm kaj pezas ĉirkaŭ 1400 g. Ĝenerale, la plej grandaj kornostrigoj troviĝas proksime de la polusaj regionoj kaj la plej malgrandaj proksime de la Ekvatoro. Inoj estas pli grandaj ol maskloj. Plenkreskuloj havas grandajn oreltufojn, ruĝecan, brunan aŭ grizan vizaĝon limigitan de nigra bordo kaj kun nigra beko centre kaj blankan makulon en la gorĝo. La irisoj estas flavaj, escepte en la raso B. v. nacurutu ĉe kiuj ĝi estas sukcenkolora. La oreltufoj ne estas vere oreloj, sed simple plumotufoj. La subaj partoj estas helaj kun bruna horizontala striado; la supraj partoj estas makulitaj je bruno. La kruroj kaj piedoj estas kovritaj el plumoj ĝis la kalkanoj.
Estas individuaj kaj regionaj varioj laŭ koloro; birdoj el sub-Arkto estas malpli striitaj, helsablokoloraj, dum tiuj de Centrameriko povas esti malhele ĉokoladbrunaj. Tiuj strigoj havas ankaŭ spektaklan duokulan vidkapablon necesa por lokigi eventualjn predojn kaj vidi en malhelo. Strigoj ne povas movi siajn okulojn kiel homoj ekzemple. Tiuj estas enfermitaj en speciala cirkla osto. Tamen, iliaj koloj povas turniĝi 270 gradojn por vidi en aliaj direktoj sen movi siajn enterajn korpojn. La aŭdkapablo de tiuj strigoj estas tiom bonkvalita —se ne pli bone— ol ilia vidkapablo. Tiu strigoj havas sterean aŭdkapablon, kiu permesas ilin trovi la precizan lokon de iliaj predoj. Tiuj birdoj havas ankaŭ tre fortajn kalkanojn.
La granda kornostrigo estas inter la plej fruaj reproduktantoj de Nordameriko. Ili reproduktiĝas en malfrua januaro aŭ frua februaro kaj ofte oni aŭskultas ilin alvokante unu la alian aŭtune, komencante en oktobro. Ili elektas partneron ĉirkaŭ decembro kaj ofte ili estas aŭdataj duope antaŭ tiu epoko. Ĉ estrigoj de pli tropikaj klimatoj, la datoj de reprodukta sezono estas iom necerta. Ili ofte uzas neston uzitan de aliaj granda birdo, foje aldonante plumojn por kovri la neston, sed kutime ne multe pli. Ili preferas nestojn de korvoj, korakoj kaj de jamajka buteo aŭ de grandaj sciuroj en Nordameriko. Tamen, ili tute ne dependas el oldaj nestoj de aliaj specioj, sed male ili povas uzi truojn en arboj kaj stumpoj, klifoj, abandonitaj konstruaĵoj kaj eĉ artefaritaj platformoj.
Kutime estas 2 ovojn en ĉiu ovodemetado, sed la kvanto povas varii el 1 ĝis 5 ovoj (5 estas tre rara). La mezaveraĝa ovolarĝo estas 46.5 mm, la mezaveraĝa longo estas 55.2 mm kaj la mezaveraĝa pezo estas 51 g. La kovado daŭras el 30 ĝis 37 tagojn, mezaveraĝe 33 tagojn. Kovado estas preskaŭ konstanta ĝis kiam la idoj estas 2semajnaĝaj. La strigidoj moviĝas al proksimaj branĉoj je 6 semajnoj kaj ekflugas post ĉirkaŭ unu semajno plia. Oni vidis idojn petante manĝon eĉ en malfrua oktobro (5 monatoj post elnestiĝo) kaj plej parto ne separiĝas el siaj gepatroj preskaŭ ĝis kiam tiuj komencas reproduktiĝi denove (kutime decembro). La birdoj povas ne reproduktiĝi dum alia jaro aŭ eĉ dua kaj estas ofte vagantoj ĝis kiam ili setlas siajn proprajn teritoriojn.
Ĉiu plenkreskulo de granda kornostrigo estas konstanta loĝanto de sia teritorio. Ovoj, idoj kaj junuloj povas esti predataj de vulpoj, kojotoj, katoj. Preskaŭ ne estas predantoj de plenkreskuloj, sed ili povas esti mortigitaj en luktoj kontraŭ agloj, neĝostrigoj kaj, ĉefe, kontraŭ alia granda kornostrigo, kio povas finiĝi en manĝo de la ĵus mortinta strigo.
Tiuj nearktisaj kaj neotropisaj birdoj ĉasas dumnokte per gvatado sur alta gvatejo kaj falŝvebante super la predo. Tiu povas esti tre varia, sed ĉefe el malgrandaj al mezgrandaj mamuloj kiel ratoj, sciuroj, muŝoj, talpoj, kamporatoj, marmotoj, mefitoj, sorikoj, vespertoj, musteloj, gerboj kaj eĉ histrikoj. Iuloke leporoj kaj kunikloj povas konsistigi la plej parton de la manĝobezono de Grandaj kornostrigoj. Birdoj konsistigas la alian grandan parton de la predoj de la Granda kornostrigo, kun birdogrando el regolo ĝis Herodiardeo. Iuloke, akvobirdoj, ĉefe fulikoj kaj anasoj, povas esti gravaj predoj; tiuj strigoj povas predi ankaŭ rabobirdojn gsix la grando de neĝostrigo. Reptilioj, amfibioj, fiŝoj, krustulojn kaj eĉ insektoj povas esti eventualaj predoj. En nordaj regionoj, kie pli grandaj predoj ne povas esti manĝataj rapide, ili povas lasi nemanĝitan manĝaĵon frostitan kaj poste varmigi ĝin per sia propra korpa varmo. Ili kutime manĝas kaj vomas manĝaĵon en la samaj lokoj.
Ili havas elstarajn aŭdkapablon kaj vidkapablon en malforta lumo. La aŭdkapablo estas multe pli pova ol tiu homa kaj same la percepto de la sonaltiĝo. Tio lasta eblas ĉar la oreloj de la strigoj ne estas samloke en ambaŭ flankoj de la kapo: la dekstra orelo estas tipe pli alta en la kranio kaj je ioma diferenca angulo. Movante aŭ turnante sian kapon ĝis la sono estas sama en ĉiu orelo, strigo povas lokigi kaj la horizontalan kaj la vertikalan direkton de sono. La okuloj de la Granda kornostrigo estas preskaŭ tiom grandaj kiom tiuj homaj kaj estas nemoveblaj en siaj ingoj. Anstataŭ turni siajn okulojn, la strigo turnas sian kapon.
La alvoko estas altatona sed laŭta "ho-ho-hu hu hu." Foje estas nur kvar silaboj anstataŭ kvin. La alvoko de la ino estas pli alta kaj laŭtiĝas fine de la alvoko. Junuloj povas produkti susurajn aŭ kriĉajn sonojn kiuj ofte povas esti konfuzitaj kun tiuj de la Turstrigo. La alvoko de la masklo estas ofte uzata en holivudaj filmoj, nedepende de kiu strigo aperas surekrane (simila al krio de jamajka buteo).
La Granda kornostrigo estas la oficiala birdo de Alberto. La Granda kornostrigo povas facile esti konfuzita kun la Bubo magellanicus, la Magelana kornostrigo (kiu iam estis konsiderata kiel apartenanta al tiu ĉi specio), kaj kun aliaj gufoj aŭ gufoj.
Estis nomita granda nombro de subspecioj. Kiel dirite supre, multaj al tiuj estas nur ekzemploj de individuoj aŭ klina variado. Diferencoj inter subspecioj estas ĉefe pri koloro kaj grando kaj ĝenerale sekvas la regulojn de Gloger kaj Bergmann.
La sinklera gufo de pleistoceno el Kalifornio, Bubo sinclairi, povus esti paleosubspecio de tiu ĉi specio (Howard 1947).
Piedodetalo de Bubo virginianus. Muntita specimeno.
La granda kornostrigo aŭ virginia kornostrigo, Bubo virginianus, estas specio de granda birdo el la ordo de strigoformaj, familio de strigedoj, kun granda plumtufo super ĉiu okulo. Ĝi estas indiĝena de Norda kaj Suda Ameriko. Ĝi estas adaptema birdo kun ampleksa teritorio, kvankam ne tiom disvastigata kiom tiu de la Turstrigo.
El búho americano[2] (Bubo virginianus), con los nombres locales en Brasil y Argentina derivados del guaraní: yacurú y jacurutú; también conocido en inglés como búho cornudo, búho tigre o búho real americano,[3] es una especie de ave de la familia Strigidae nativo de América. Es un ave extremadamente adaptable que vive en una gran extensión de territorio y es el búho más ampliamente distribuido en las Américas. Si bien es de gran tamaño, presenta gran variación (en tamaño y coloración) dentro de su rango de distribución (no consistente con la latitud). De todas las especies del género Bubo que hay en el mundo, el búho cornudo es el único que vive en América. Habita una gran variedad de hábitats, áreas abiertas asociadas a bosques y cuerpos de agua, bosques tropicales, templados, pantanosos y de coníferas, además manglares, desiertos y páramos, y asimismo vegetación secundaria y parques (este búho está asociado a paisajes fragmentados por ser tolerante a las actividades humanas). Está estrechamente relacionado con el Búho real que ocupa el mismo nicho ecológico en Eurasia. El busardo colirrojo podría considerarse su equivalente ecológico diurno pues comparte con el búho americano hábitats, presas y hábitos de anidación similares.
El búho americano forma parte del género Bubo, que puede incluye otras especies de búho distribuidos predominantemente por Eurasia y África. Se cree que los antepasados de este búho llegaron a América a través del Puente de Beringia. Posteriormente, el Búho magallánico se separó del búho americano cuando este ya se encontraba ampliamente distribuido por América. Según el consenso general entre los científicos la división entre el búho nival y el búho americano se produjo en Eurasia y desde allí emigraron como especies separadas a América. Se ha sugerido que el búho americano y el búho real puedan ser conespecíficos, es decir, que ambos sean de la misma especie. Sin embargo, los estudios genéticos revelan que es el búho nival la especie viva más estrechamente relacionada con el búho americano. Se han encontrado restos fósiles del Pleistoceno de búhos pertenecientes al género Bubo en América del Norte pero parece ser que son especies diferentes o paleosubespecies del búho americano.
El número de subespecies es muy debatido entre los científicos. Generalmente, 12 subespecies son reconocidas:
Búho americano de Baja California (Bubo virginianus elachistus) De color similar al pacificus pero aún más oscuro y con más barras, parecido a un saturatus miniaturizado. Es considerablemente más pequeño que pacificus;se la considera la subespecie más pequeña.[4][5] Los machos tienen una longitud en el ala de 30 a 33 cm, una longitud de la cola de 17 a 20 cm y una longitud del pico de 3,3 a 3,8 cm. Vive en la misma zona todo el año y no realiza migraciones estacionales.
Búho americano nororiental (Bubo virginianus heterocnemis) Se reproduce en el este de Canadá (norte de Quebec, Labrador, Terranova). Su área de reproducción parece estar delineada al sur por el Río San Lorenzo. En invierno, esta raza puede dispersarse hacia el sur a lo largo de Ontario hasta el noreste de los Estados Unidos. Esta subespecie puede ser sinónimo de saturatus, aunque su distribución se aleja bastante de esta raza al este. B. v. heterocnemis está rodeado al oeste por la subespecie bastante más pálida subarcticus y al sur por virginianus, con esta última subespecie los rangos se superponen y pueden llegar a hibridar. Es una raza bastante oscura y gris, con una multitud de barras en el plumaje. Una forma bastante oscura y gris, fuertemente barrada. Algunos naturalistas defienden[¿quién?] que es la subespecie de mayor tamaño y los machos tienen un ala con una longitud de entre 35 y 36 cm y las hembras entre 37 y 39 cm.[6][7][8] En ambos sexos, la cola mide 22 a 25 cm y el pico es de 3,8 a 4,8 cm.
Búho americano de Alaska (Bubo virginianus lagophonus)
Búho americano del Yucatán (Bubo virginianus mayensis) Residente todo el año en la misma zona, sin realizar migraciones estacionales. Es una subespecie medianamente pálida, bastante similar a pallescens tanto en tono como en marcas ventrales. B. v. Mayensis es más pequeño que todas las subespescies de Norteamérica y es solo un poco más grande que elachistus. Los machos tienen unas alas con una longitud de 29-34 cm y una cola de 18-19 cm. Las hembras, en cambio, tienen unas alas de 30-35 cm de longitud y la cola entre 19-21 cm.
Búho americano centroamericano (Bubo virginianus mesembrinus)
Búho americano sudamericano o Ñacurutú (Bubo virginianus nacurutu) Incluye las subespecies propuestas scotinus, elutus y deserti. Es un ave pálida de color marrón en tonos tierra. Las aves del interior semiárido de Brasil, a menudo, son más blancas contra un fondo gris oscuro en las coberteras de la cola y los penachos en forma de orejas (a veces separadas como deserti). Esta especie es menos oscura que nigrescens. Es la única subespecie donde el iris es ámbar, no amarillo. B. v. nacurutu es una raza de tamaño mediano, más pequeña que la mayoría de América del Norte, pero no tan pequeña como algunas de las especies mexicanas. La longitud del ala es de 33–35 cm en los machos y 34-37 cm en las hembras. La cola en ambos sexos puede variar de 18 a 21 cm. La característica más notable de esta especie es su gran pico,[cita requerida] de 4,3 a 5,2 mm (1.7 a 2.0 pulgadas), que es el pico más grande en comparación con su tamaño total de entre todas las subespecies de búho americano.[7][9]
Búho americano andino (Bubo virginianus nigrescens) Es una subespecie oscura de color marrón grisáceo con marcadas manchas oscuras. Esta es la especie de color más oscuro, aunque compite por ello con saturatus y elachistus. Esta especie apenas tiene el matiz rojizo de otras subespecies, aunque algunos nigrescens pueden tener un disco facial de color canela. Es la subespecie más grande de Sudamérica, tiene una longitud de ala de 34–36 cm en machos y 35–38 cm en hembras. La cola en ambos sexos puede variar de 18 a 21 cm. La longitud del pico es de 4 a 5 cm, relativamente grande como sucede en nacurutu.
Búho americano de California (Bubo virginianus pacificus) Plumaje bastante marrón y con vermiculaciones menos marcadas que en saturatus pero más marcadas que en pallescens. Las garras están manchadas de oscuro. El disco facial a menudo tiene manchas oscuras. Esta raza de cuerpo bastante pequeño tiene el registro de menor peso en un macho del búho americano. La longitud del ala es de 30-36 cm en los machos y 33–37 cm en las hembras. La masa corporal varía de 680 a 1,272 g en los machos y de 825 a 1,668 g en las hembras. La longitud de la cola es de 17 a 21 cm y de 20 a 23 cm en machos y hembras, respectivamente.
Búho americano del desierto (Bubo virginianus pallescens) Es una subespecie de color beige oscuro con vermiculaciones en la parte inferior. Una raza pequeña, tiene una de longitud de ala ligeramente mayor que el pacificus, pero pesa menos de media. La longitud del ala es de 31–36 cm en los machos y 33–38 cm en las hembras. La masa corporal varía de 724 a 1.257 g en machos y de 801 a 1.550 g en hembras. En ambos sexos, la longitud de la cola es de 19 a 23 cm (7,5 a 9,3 pulgadas) y la longitud del pico es de 3,3 a 4,3 cm.
Búho americano del Pacífico (Bubo virginianus saturatus) Una subespecie oscura y pardusca en general con la parte inferior fuertemente barrada y moteada, con una base de color marrón oscuro. Las aves del interior (para algunos científicos separadas en lagophonus) tienden a tener una base más grisácea, siendo las lechuzas costeras puramente marrones. Por lo demás, los búhos del interior y de la costa son prácticamente iguales. El disco facial puede variar entre gris, gris rojizo y rojo oscuro. Las patas suelen ser de color gris oscuro y están más fuertemente barradas que en las otras subespecies norteamericanas. Es una subespecie bastante grande en líneas generales y los búhos de Alaska probablemente superen a todas las demás subespecies en tamaño con la excepción de heterocnemis. La longitud del ala es de 33–37 cm en los machos y 33–40 cm en las hembras. La longitud de la cola es de 19 a 24 cm y de 19 a 25 cm en machos y hembras respectivamente. En ambos sexos, la longitud del pico y tarso es de 3,5 a 4,4 cm.
Búho americano norteño (Bubo virginianus subarcticus) Esta es la subespecie más pálida de búho americano, con el color de fondo esencialmente blanquecino con un leve tono amarillo brillante en la parte superior; la nitidez de las vermiculaciones negras en la parte inferior es variable entre barras más definidas y otras más difusas. Esta raza muestra poca o ninguna coloración rojiza. Muestra una gran variación en su aspecto entre poblaciones siendo las de Estados Unidos de color grisáceo y bastante barrados y los de las zonas subárticas de Canadá que son de color muy pálido y apenas barrados. Las aves jóvenes muy pálidas son similares a las lechuzas nivales hembra y pueden ser identificadas erróneamente desde una distancia lejana. En el oeste de Canadá, subarcticus puede hibridar con saturatus y lo mismo sucede con heterocnemis en el este. En ambos casos, pueden producir híbridos de aspecto intermedio de tono rojizo, parecido a un virginianus pero con un contraste de colores más agudo. La longitud del ala es de 32–37 cm (12.7–14.6 in) en los machos y 33–39 cm en las hembras. La masa corporal varía de 865 a 1,460 g (1.907 a 3.219 lb) en los machos y de 1,112 a 2,046 g en las hembras. La longitud de la cola es de 20 a 22 cm y de 20 a 24 cm en machos y hembras, respectivamente. La longitud del pico es de 3,5 a 4,3 cm en ambos sexo.
Búho americano oriental (Bubo virginianus virginianus) La subespecie nominal es una forma de tono medio, ni muy oscura ni muy pálida. Tiende a tener un plumaje con bastante tonalidad rojiza y abundante barrado de color pardo oscuro en contraste con el color de fondo más claro. Los dedos suelen ser de color castaño, amarillento o crema y las patas están profusamente barradas. El disco facial es, por lo general, de un color rojo o anaranjado. Esta es una subespecie moderadamente grande, con una longitud del ala de 31–37 cm en machos y 34–38 cm en las hembras. mujeres. Esta es la subespecie conocida de mayor masa corporal, aunque esto podría cambiar oyes se desconoce los pesos de la mayoría de las subespecies, llegando los machos a pesar de 985 a 1,588 g y las hembras de 1,417 a 2,503 g. La longitud de la cola es de 19 a 23 cm (7.5 a 9.3 in) y la longitud del pico de 3,5 a 5 cm. B. v. virginianus es también la subespecie con los penachos más grandes en relación con su tamaño general.
El búho americano es el búho más pesado existente en América Central y del Sur y es el segundo búho más pesado en América del Norte, después del búho nival con el que esta estrechamente relacionado. Tiene una constitución fuerte, con un cuerpo en forma de barril, una cabeza grande y alas anchas. Su tamaño puede variar considerablemente en su rango, con poblaciones en el interior de Alaska y Ontario siendo más grandes y poblaciones en California y Texas siendo más pequeñas, aunque las de la península de Yucatán y Baja California parecen ser aún más pequeñas. Los búhos adultos tienen una longitud de 43 a 64 cm, con un promedio de 55 cm y poseen una envergadura de 91 a 153 cm, con un promedio de 122 cm. Las hembras son algo más grandes que los machos. De media el peso corporal es de 1.608 g en las hembras y 1.224 g para los machos. Dependiendo de la subespecie, el peso máximo puede alcanzar 2,503 g.
La longitud del ala es de 29–40 cm, siendo unas alas relativamente pequeñas en comparación con la masa corporal del ave. La cola, que es relativamente corta, como es típico en la mayoría de los búhos, tiene una longitud de 17 a 25 cm. Al igual que otras especies de búhos, el búho americano es capaz de realizar un "vuelo silencioso", que es la forma en que los búhos vuelan sin hacer casi ningún ruido perceptible, a pesar de su gran tamaño. Esto es posible gracias a tres componentes de la estructura del ala del búho.
Las patas, los pies y las garras son grandes y poderosos. La longitud del pie completamente extendido, de una garra a otra, es de alrededor de 20 cm, en comparación con los 8 cm del búho chico, los 13 a 15 cm en las lechuza común y los 18 cm en el cárabo lapón. Los búhos americanos pueden aplicar una gran fuerza con sus garras, una presión considerablemente mayor que la que la mano humana es capaz de ejercer. En algunas hembras grandes, el poder de agarre del gran búho americano puede ser comparable a especies de rapaces mucho más grandes como el águila real. El pico duro e inflexible del búho americano mide 3.3–5.2 cm de largo.
Las aberturas externas del oído, que están ocultas por plumas en los costados de la cabeza, son relativamente pequeñas, con el oído izquierdo ligeramente más grande que el derecho. Al igual que otras especies nocturnas, el búho americano tiene los oídos asimétricos lo que le permite la triangulación de los sonidos al cazar en la oscuridad. Los oídos a diferentes alturas, aunque la diferencia no sea muy grande, se diferencian lo suficiente como para que el búho pueda usar el tiempo y la dirección de las ondas de sonido que golpean cada oído para ubicar con precisión la presa. La forma de disco de sus caras también ayuda a dirigir los sonidos que escuchan hacia sus oídos. Si bien se desconoce la verdadera naturaleza o propósito de los penachos emplumados con forma de orejas que están presentes en el búho americano, los investigadores coinciden en que los mismos no juegan ningún papel en la capacidad auditiva del búho. Se estima que su audición es hasta diez veces mayor que la de un ser humano.
Los ojos del búho americano, un poco más pequeños que los ojos de un ser humano, son grandes incluso para un búho y se encuentran entre los ojos más grandes de todos los vertebrados terrestres proporcionalmente al tamaño general del cuerpo. El búho americano tiene ojos cilíndricos que crean una mayor distancia desde la lente del ojo hasta la retina, lo que le permite actuar más como un teleobjetivo para una mejor visión a mayor distancia que la que le proporcionaría unos ojos redondos. Sus ojos están visualmente muy adaptados para la caza nocturna y proporcionan un campo de visión amplio, casi completamente binocular. En lugar de girar los ojos, el búho debe girar toda su cabeza, y puede girar su cuello 270 °. El iris es amarillo, excepto en el búho americano sudamericano que son de color ámbar (B. v. nacurutu).
La finalidad principal del plumaje del búho americano es el camuflaje. Las partes inferiores del cuerpo son generalmente claras con vermiculaciones pardas; las partes dorsales y la parte superior de las alas son moteados de diversos tonos de marrón. Todas las subespecies también tienen vermiculaciones, en distinta intensidad, en los lados.
Posee una mancha blanca de tamaño variable en la garganta. Esta mancha puede extenderse hasta la mitad del pecho e, incluso en ejemplares particularmente pálidos, puede agrandarse hasta el vientre. Los búhos americanos de Sudamérica suelen tener esta mancha blanca más pequeña y rara vez se extiende hasta el pecho. Existen variaciones en la coloración del plumaje tanto individuales como regionales, con los búhos del subártico siendo de color claro y tonos pálidos, mientras que los de la costa del Pacífico de Norteamérica, los de América Central y gran parte de Sudamérica suelen tener un color marrón oscuro parcheado con manchas negruzcas. La piel de los pies y las patas, aunque casi completamente oculta tras las plumas, es negra. El pico y las garras es de color gris oscuro.
Todos los búhos americanos tienen un disco facial. Este puede ser de color rojizo, marrón o gris (variando según la zona geográfica y la subespecie) y está demarcado por un borde oscuro. Las "orejas" de esta especie son en realidad penachos de plumas. El propósito de los mismos no se ha identificado completamente, pero está generalmente aceptada la teoría de que sirven como una señal visual en las interacciones territoriales y sociosexuales con otros búhos.
El búho americano se distribuye por todo América del Norte con la excepción de las zonas más frías del ártico donde es sustituido por el búho nival. En América Central su distribución está más fragmentada y solo se encuentra en enclaves aislados. En América del Sur se distribuye por el norte del subcontinente desde Colombia hasta las Guayanas y el noreste de Brasil y también en las cordilleras andinas de Ecuador y Perú. En el sur de Sudamérica también ocupa una amplia zona entre Bolivia y el sureste Brasil hasta el norte de Argentina; más al sur es sustituido por el búho magallánico. La especie esta ausente de lo más profundo de los bosques tropicales del Amazonas, así como de islas del Caribe. Es la segunda especie de búho con una mayor distribución en las Américas tras la Lechuza común.
Esta especie de búho se encuentra entre las especies de aves más adaptables del mundo en lo que se refiere a su hábitat. Puede vivir en árboles pertenecientes a todo tipo de hábitats: bosques templados, bosques de coníferas, bosques mixtos, bosques tropicales, pampas, praderas, zonas montañosas, desiertos, tundra, costas rocosas, manglares e incluso algunas áreas urbanas. Se encuentra ausente de las áreas con climas más extremos como el interior de los desiertos de Mojave y Sonora. También evita las zonas de bosque profundo y prefiere vivir en áreas de bosque más fragmentado con zonas abiertas donde cazar y grupos de árboles donde descansar y refugiarse. En lugares abiertos como praderas y desiertos pueden residir todo el año mientras existan cañones rocosos, barrancos o zonas arboladas que les sirvan de refugio y lugar de anidación.
En las zonas montañosas de América del Norte, generalmente están ausentes por encima del límite del bosque, pero se pueden encontrar de hasta 2,100 m en California y 3,300 m en las Montañas Rocosas. En las montañas de los Andes, por otro lado, se han adaptado a ser verdaderas aves montanas, a menudo se encuentran al menos a 3,300 msnm y se registran regularmente en zonas de pastizales de la Puna sin árboles a 4,100 a 4,500 m en Ecuador y Perú. En general, es raro verlos en humedales. Aunque se adapta bien a la vida en áreas urbanas prefiere zonas con menor actividad humana como grandes parques y zonas de cultivo. Todos los búhos americanos son aves residentes que no realizan migraciones salvo cuando las aves no emparejadas o ejemplares jóvenes se mueven en busca de pareja o territorio.
Anida en oquedades de troncos, y puede poner de dos a tres huevos. Se alimenta de pequeños mamíferos, reptiles e incluso peces. Se ha reproducido en cautiverio. Se utilizó y se sigue utilizando para cetrería.
Aunque la especie presenta aparentemente amplia distribución en México, existe poca información sobre el estado actual de sus poblaciones y rango de distribución. Al parecer, va desde el norte del país, incluyendo Baja California Norte y Sur, hasta el sur de México incluyendo la Península de Yucatán. La IUCN2019-1 considera a la especie como de preocupación menor. Los principales riesgos que amenazan a la especie son la pérdida del hábitat, disminución de presas, cacería ilegal, uso de plaguicidas y colisión con automóviles, cables eléctricos y construcciones.[10]
El búho americano (Bubo virginianus), con los nombres locales en Brasil y Argentina derivados del guaraní: yacurú y jacurutú; también conocido en inglés como búho cornudo, búho tigre o búho real americano, es una especie de ave de la familia Strigidae nativo de América. Es un ave extremadamente adaptable que vive en una gran extensión de territorio y es el búho más ampliamente distribuido en las Américas. Si bien es de gran tamaño, presenta gran variación (en tamaño y coloración) dentro de su rango de distribución (no consistente con la latitud). De todas las especies del género Bubo que hay en el mundo, el búho cornudo es el único que vive en América. Habita una gran variedad de hábitats, áreas abiertas asociadas a bosques y cuerpos de agua, bosques tropicales, templados, pantanosos y de coníferas, además manglares, desiertos y páramos, y asimismo vegetación secundaria y parques (este búho está asociado a paisajes fragmentados por ser tolerante a las actividades humanas). Está estrechamente relacionado con el Búho real que ocupa el mismo nicho ecológico en Eurasia. El busardo colirrojo podría considerarse su equivalente ecológico diurno pues comparte con el búho americano hábitats, presas y hábitos de anidación similares.
Bubo virginianus Bubo generoko animalia da. Hegaztien barruko Strigidae familian sailkatua dago.
Amerikanhuuhkaja (Bubo virginianus) on amerikkalainen suurikokoinen pöllö.
Linnun pituus on 46–63,5 cm, siipien kärkiväli 91–152 cm ja paino 900–1 800 g. Kooltaan amerikanhuuhkaja on selvästi huuhkajaa pienempi. Sen väritys vaihtelee punaruskeasta harmaaseen ja mustavalkoiseen. Sillä on keltaiset silmät oranssin naamakiehkuran keskellä ja pitkät korvatöyhdöt. Naaras on koirasta kookkaampi.
Amerikanhuuhkaja elää kaikissa kolmessa Uuden maailman maanosassa, pohjoisessa Alaskasta ja Kanadan keskiosista Yhdysvaltain kautta Keski-Amerikkaan ja monin paikoin Etelä-Amerikassa, kuten Andeilla, Amazonin altaan eteläpuolella ja aivan mantereen koillisella rannikkokaistaleella. Sen elinympäristön ala on noin 24 miljoonaa neliökilometriä ja maailman populaation koko on noin 5,3 miljoonaa yksilöä. Se on enimmäkseen paikkalintu, jonka pohjoisimmat kannat voivat muuttaa hieman etelämmäksi talveksi.
Lajille kelpaavat monenlaiset elinympäristöt tiheistä metsistä aavikoihin ja kaupunkien puistoihin.
Amerikanhuuhkaja ei rakenna varsinaista pesää, vaan pesii esimerkiksi muiden lintujen, kuten varislintujen, haukkojen tai haikaroiden vanhoihin pesii, rakennuksiin, kalliojyrkänteen ulkonemalle, puun onkaloon tai vanhaan oravanpesään. Naaras munii 2–4 munaa, joita se hautoo 26–35 päivää. Poikaset lähtevät pesästä 6–7 viikon ikäisinä ja oppivat lentämään 9–10 viikkoisina, jonka jälkeen emot ruokkivat niitä vielä joidenkin viikkojen ajan. Poikaset itsenäistyvät syksyllä ja lähtevät vaeltamaan jopa 250 kilometrin päähän. Laji on yksiavioinen ja sen reviirin koko on noin 2,5 neliökilometriä. Vankeudessa se on elänyt yli 30-vuotiaaksi, luonnossa vanhin yksilö on ollut 13-vuotias.
Amerikanhuuhkajan pääravintoa ovat kanit ja jänikset, mutta sen ruokavalioon kuuluvat myös jyrsijät ja muut nisäkkäät, linnut, matelijat, sammakkoeläimet, kalat, kovakuoriaiset ynnä muut selkärangattomat ja tuoreet raadot.
Amerikanhuuhkaja (Bubo virginianus) on amerikkalainen suurikokoinen pöllö.
Bubo virginianus
Le Grand-duc d'Amérique[a] ou Grand-duc de Virginie (Bubo virginianus) est une espèce de rapaces nocturnes appartenant à la famille des Strigidae et à la sous-famille des Striginae. Il est souvent comparé avec son cousin le Grand-duc d'Europe avec qui il partage de nombreux points communs.
Cet oiseau aux aigrettes caractéristiques est le deuxième plus grand des hiboux d'Amérique après le Harfang des neiges; sa taille varie cependant significativement selon son habitat et l'abondance de la nourriture[4].
Avec un bec crochu, de grandes ailes, des serres puissantes, le Grand-duc est parfaitement adapté à la chasse nocturne d'animaux de petite taille. Ses yeux jaunes perçants et ses aigrettes en font un oiseau impressionnant pour l'homme.
Cet oiseau mesure 45 à 63 cm de longueur pour une envergure de 90 à 162 cm et une masse de 675 g à 2,5 kg. Il ne présente pas de dimorphisme sexuel en termes de couleurs, mais en termes de grosseur, les femelles étant un tiers plus grosse que les mâles comme chez la plupart des oiseaux de proies.
Il a la gorge blanche.
Le Grand-duc d'Amérique niche dans la majeure partie du continent américain. Son aire de répartition s'étend loin au nord, occupant une bonne partie du Canada, et en Amérique du Sud jusqu'au nord de l'Argentine, ainsi qu'au Brésil et en Bolivie.[5]
Cet oiseau est un des hiboux les plus adaptables, résidant dans les arbres de tout type de forêts, de jungles, de prairies, de déserts, de toundras, de mangroves et même de zones urbaines. Il évite cependant les zones trop extrêmes, comme le cœur des déserts, ou trop boisées. On le retrouve rarement en altitude en Amérique du Nord[6], alors qu'il s'est bien adapté aux plateaux des Andes dans le sud de son aire de répartition.[7]
Généralement sédentaire, cet oiseau défend son territoire, surtout en période de reproduction, avec toutefois des jeunes ayant un comportement non territorial[8].
Vocalisations : Très bruyant à la saison de reproduction, il émet un hululement puissant[9], typique du chant des hiboux[10].
Il niche dans d'anciens nids d'autres grands oiseaux, dans des trous d'arbres, des corniches de falaise et même au sol.
Habituellement le plus actif au crépuscule et à l'aube, c'est un chasseur efficace. Il bénéficie d'une bonne vision nocturne et d'une bonne acuité visuelle[11] ainsi que d'une ouïe particulièrement développée.
Il capture surtout de petits mammifères (campagnols, etc.) dont certains ont développé des "comportements anti-prédateurs"[12], des insectes, des reptiles, des amphibiens et des oiseaux (y compris d'autres rapaces nocturnes et des gélinottes).
Il peut chasser et manger les moufettes, grâce à son odorat très peu développé. La prédation a été observée sur tous les types de mouffettes nord américaines, dans certains cas sur des animaux au moins trois fois plus gros que le Grand-duc prédateur [13],[14],[15], et un nid a été trouvé contenant les restes de 57 mouffettes de tous types [16]. Une conséquence est que les nids de Grands-ducs ont tendance à manifester une forte odeur de mouffette[17],[18].
Cet oiseau est sédentaire. Après leur émancipation, les jeunes explorent leur environnement pour trouver un territoire disponible et leur convenant et s'y établir.
L'espèce est en régression, probablement à cause de la destruction, fragmentation et régression de ses habitats, et à cause d'une dégradation de la qualité de certaines de ses proies, contaminées par des pesticides, métaux lourds (plomb notamment, qui est cause de saturnisme aviaire[19]. Des parasitoses ou attaques des jeunes au nid par des tiques ou mouches hématophages peuvent affaiblir les jeunes et faciliter certaines maladies (leucocytozoonoses)[20].
Bubo virginianus
Le Grand-duc d'Amérique ou Grand-duc de Virginie (Bubo virginianus) est une espèce de rapaces nocturnes appartenant à la famille des Strigidae et à la sous-famille des Striginae. Il est souvent comparé avec son cousin le Grand-duc d'Europe avec qui il partage de nombreux points communs.
O bufo americano (Bubo virginianus) é unha especie de ave estrixiforme da familia dos bufos (Strigidae). É nocturna, de plumaxe raiada.
O bufo americano (Bubo virginianus) é unha especie de ave estrixiforme da familia dos bufos (Strigidae). É nocturna, de plumaxe raiada.
Il gufo della Virginia (Bubo virginianus Gmelin, 1788) è un grande rapace notturno della famiglia degli Strigidi.[2]
Misura da 50 a 66 cm, pesa dai 675 ai 2500 grammi e ha un'apertura alare di 140–170 cm. È il gufo più grande del continente americano. Ha una corporatura molto robusta con piedi grandi e artigli affilati. Il piumaggio è vario, ma sempre di tonalità brune tranne sulla gola che è sempre bianca. Si va dal marroncino chiaro, quasi biancastro, delle sottospecie che vivono più a nord, al bruno scuro di quelle che vivono nelle foreste. In tutti i casi comunque il piumaggio è striato di nero dal capo alla coda. Il becco è adunco, gli occhi giallo chiaro, ma il tratto distintivo di questo gufo sono i grandi ciuffi di piume sulle orecchie.
Vive in tutto il continente americano dal Canada fino al Cile e all'Argentina (è stato avvistato anche vicino allo Stretto di Magellano e più a sud sulle isole della Georgia del Sud e sulle Sandwich Australi), con l'esclusione delle zone polari, del fitto della foresta amazzonica e di alcune isole dei Caraibi.
Il largo areale permette al gufo della Virginia di frequentare posti assai diversi tra loro. Principalmente lo si incontra nei fitti boschi di conifere o di latifoglie, ma è presente anche lungo burroni e canyon rocciosi, nel deserto e nella taiga canadese, ad altezze variabili ma anche in alta montagna.
È un rapace stanziale e solitario, fortemente territoriale. Difende assiduamente i propri territori di caccia e di nidificazione, non esitando ad attaccare qualsiasi intruso, compreso l'uomo. Sebbene veda anche di giorno, diviene attivo soprattutto la notte sia perché la vista è migliore, sia perché le prede del gufo sono animali notturni. Il volo è silenzioso, grazie alle soffici piume, ed inoltre è dotato di un udito eccellente. Al contrario, l'olfatto è estremamente limitato, quasi assente, il che lo rende capace di cacciare le moffette senza temere le secrezioni dall'odore nauseabondo che usano come difesa. I piccoli se si sentono minacciati gonfiano il piumaggio per sembrare più grandi e minacciosi.
Il gufo della Virginia, come gli altri gufi, è un carnivoro. Si nutre solitamente di piccoli mammiferi come conigli, topi, scoiattoli, marmotte, moffette e ratti. Mangia anche altri uccelli di piccole e grandi dimensioni come quaglie e anatre, o oche e tacchini, e talvolta persino altri gufi. Non disdegna rane e altri anfibi, rettili e raramente anche insetti. Le parti non digeribili delle prede, come ossa e piume, vengono rigettate sotto forma di borre.
Il periodo riproduttivo del gufo della Virginia inizia tra gennaio e i primi di febbraio. Maschi e femmine diventano molto loquaci, modulando una certa quantità di note per attrarre il partner. Una volta accoppiati, la femmina depone da una a cinque (in genere due o tre) uova nella cavità di un albero o nei nidi abbandonati di altri uccelli. Il periodo di incubazione delle uova è di circa 30 giorni, dopodiché i genitori accudiranno i piccoli per oltre un mese dopo l'impiumazione che avviene ai due mesi dalla schiusa.
Esistono 14 sottospecie di Bubo virginianus:[2]
Il gufo della Virginia (Bubo virginianus Gmelin, 1788) è un grande rapace notturno della famiglia degli Strigidi.
De Amerikaanse oehoe (Bubo virginianus) is een algemene uilensoort van het Amerikaanse continent.
Met een grootte van 43-55 cm is de oehoe één van de grootste uilensoorten, maar een slag kleiner dan de Europese oehoe. Het dier heeft duidelijk horizontale oorpluimen. Het verenkleed is bruin.
's Nachts gaat deze soort op jacht naar kleine zoogdieren, vogels, reptielen en ongewervelde dieren. De grootte van de prooi varieert van grote insecten tot skunks, konijnen en ruigpoothoenders. De oehoe gebruikt vaak verlaten nesten van buizerds als nest. Daarnaast nestelt hij ook in grote boomholten of menselijke bouwsels.
Deze vogel is in een groot aantal biotopen te vinden: laagland- en bergbossen, savannes, bouwland en zelfs voorsteden.
De soort telt 14 ondersoorten:
De Amerikaanse oehoe (Bubo virginianus) is een algemene uilensoort van het Amerikaanse continent.
Amerikahubro (Bubo virginianus) er en ugle i gruppen Bubo. Den hører hjemme i både Nord- og Sør-Amerika, men er ikke fullt så vanlig som tårnuglen. Amerikahubro er aldri blitt observert i palearktis. Den er provinsfugl for den canadiske provinsen Alberta. Amerikahubro kan lett forveksles med Bubo magellanicus, som man en tid trodde tilhørte denne arten.
Amerikahubro måler fra 46 til 68 cm og har et vingespenn på 101 til 152 cm. En gjennomsnittlig størrelse er 55 cm med et vingespenn på 124 cm og vekt på 1400 gram. Hunnen er større enn hannen, og de største individene finnes i de nordligste regionene. Mot ekvator er de gjerne mindre.
Voksne fugler har store øredusker, rødlig, brunt eller grått ansikt og en hvit flekk på halsen. Iris er gul, unntatt for arten B. v. nacurutu, som har en amber farge på iris. Øreduskene er ikke ører, men fjærdusker. Legger og føtter er dekket av fjær. Undersiden av fuglen er lys med brune kanter. Det er både individuelle og regionale variasjoner i fargene; fugler fra nord har en lysebrun farge mens fugler fra Sentral-Amerika kan være mørk sjokoladebrune.
Amerikahubroen har et ekstremt godt syn i lite lys, noe som er nødvendig for å se byttet også i mørke. Fordi den ikke kan bevege øynene, kan den vri halsen i 270 grader for å se i andre retninger uten å flytte hele kroppen. Øynene er nesten like store som menneskeøyne og ligger fast i øyehulen.
Også hørselen er svært god. Hørselen oppfatter dybde bedre enn mennesket og fanger også opp høydeforskjell. Fordi ugleører ikke ligger likt på hver side av hodet, det høyre øret er litt høyere enn det venstre og har en litt annen vinkel i plasseringen, kan en ugle som snur og bikker på hodet, fastlegge både horisontal og vertikal retning av lyd. Ettersom de hører i stereo, kan de plassere byttet nøyaktig ut fra lyden.
Amerikahubro finnes nesten over hele Nord- og Sør-Amerika. De finnes i de fleste omgivelser, men er ikke så vanlige i de mest ekstreme områdene (tundra, sentrale ørkenområder og tykke regnskoger). Men den finnes i blandingsskog, tropisk regnskog, pampas, prærie, fjellområder, klippekyst og mangrovesumper, til og med i byområder.
Fuglene jakter om natten ved å vente på et utsiktspunkt og kaste seg ned på byttet, som kan variere mye, men for det meste er små til middels store pattedyr som rotter, ekorn, mus, vånd, murmeldyr, skunker, spissmus, flaggermus, vaskebjørner, katter og til og med trepinnsvin. Harer og bomullshalekaniner kan også etes, så vel som fugler av ulike slag fra fuglekonge til hegre. Dette inkluderer sothøner og ender, men også rovfugler som snøugler og fiskeørn kan være på menyen sammen med krypdyr, amfibier, fisk, krepsdyr og insekter. I nord, hvor større bytte ikke spises opp med det samme kan den la maten fryse og siden tine den opp igjen med sin egen kroppsvarme.
Det blir ofte sagt at amerikahubro er den farligste uglen, og det er rapportert at den har drept mennesker. Det bør i den forbindelse nevnes at slike angrep ikke er for mat og at det eneste kjente dødelige angrepet ble forårsaket av offeret selv, da han prøvde å stjele egg eller kyllinger fra reiret til hubroen.
Amerikahubro er en av de fugler som tidligst får unger i Nord-Amerika. Man hører fuglene kalle fra oktober, og i desember har de valgt make. Da kan man høre dem i duett. Kallingen er en dyp, men høylytt «ho-ho-hoo hoo hoo». Noen ganger er det bare fire stavelser i stedet for fem. Hunnens ligger høyere enn hannens og stiger i tone mot slutten. Ungfuglenes hissing og skrikende lyder blir ofte tatt for å komme fra tårnugler.
Så legges eggene i januar eller tidlig i februar. For fugler i mer tropisk klima er sesongen mer ubestemmelig.
Amerikahubro tar ofte over reir etter andre større fugler, noen ganger legger de fjær til i reiret, men til vanlig ikke mye mer. De kan velge seg gamle reir etter kråke, ravn, hauk eller store ekornreir. Men de er ikke avhengige av gamle reir og kan bruke huler i trær, stein, fraflyttede bygninger eller kunstige plattformer.
Vanligvis er det to egg i hvert kull, men det er variasjoner mellom ett og fem. Gjennomsnittsegget er 46,5 mm bredt og 55,2 mm langt. Vekta ligger omkring 50 gram. Rugeperioden strekker seg fra 30 til 37 dager, i snitt 33 dager. Så følger en periode på to uker med kontinuerlig foring, siden reduseres matingen. Etter seks uker flytter unge ugler ut på greiner i nærheten, en uke seinere begynner de å fly. Men man har sett at de tigger foreldrene om mat sent i oktober, fem måneder etter at de forlot reiret. De forlater ikke foreldrene før like før disse starter med å forberede et nytt kull. Ungene kan bruke et par år på å etablere seg i egne territorier, som så blir deres permanente tilholdssted.
Egg, unger og ungfugl er byttedyr for rødrever, coyoter, vaskebjørner, ville katter og huskatter. Det er nesten ingen som angriper voksne amerikahubroer, men de kan bli drept i konfrontasjoner med ørner, snøugler og andre amerikahubroer. Slike kamper kan ende med at seierherren spiser taperen.
Amerikahubro (Bubo virginianus) er en ugle i gruppen Bubo. Den hører hjemme i både Nord- og Sør-Amerika, men er ikke fullt så vanlig som tårnuglen. Amerikahubro er aldri blitt observert i palearktis. Den er provinsfugl for den canadiske provinsen Alberta. Amerikahubro kan lett forveksles med Bubo magellanicus, som man en tid trodde tilhørte denne arten.
Puchacz wirginijski (Bubo virginianus) – gatunek ptaka z rodziny puszczykowatych (Strigidae), zamieszkujący Amerykę Północną, Środkową i Południową. Teren lęgowy sięga od północnej granicy lasu na Alasce i w Kanadzie, przez Stany Zjednoczone, Meksyk, kraje Ameryki Środkowej. W Ameryce Południowej występuje w Wenezueli, Kolumbii, Peru, Boliwii, Brazylii, Paragwaju i Argentynie.
Puchacz wirginijski zamieszkuje zależnie od podgatunku[3][4][5]:
Lasy liściaste, mieszane i iglaste. Przebywa w zwartych drzewostanach, zagajnikach, małych laskach, dużych parkach miejskich.
Poluje na małe i średnie ssaki (np. szczury, króliki i skunksy) i ptaki (np. inne sowy, krukowate, kaczki) oraz czasami na gady, płazy i duże owady.
Puchacz wirginijski (Bubo virginianus) – gatunek ptaka z rodziny puszczykowatych (Strigidae), zamieszkujący Amerykę Północną, Środkową i Południową. Teren lęgowy sięga od północnej granicy lasu na Alasce i w Kanadzie, przez Stany Zjednoczone, Meksyk, kraje Ameryki Środkowej. W Ameryce Południowej występuje w Wenezueli, Kolumbii, Peru, Boliwii, Brazylii, Paragwaju i Argentynie.
A jacurutu (Bubo virginianus), também conhecida como corujão-orelhudo, jucurutu, mocho-orelhudo ou corujão-da-virgínia, é uma coruja de grande porte nativa das Américas. É uma ave extremamente adaptável com uma vasta distribuição, sendo a mais amplamente distribuída do continente.[2] Sua alimentação consiste em coelhos e lebres e ratos, apesar de caçar livremente qualquer animal que consiga, incluindo roedores e outros pequenos mamíferos, mamíferos de médio porte, aves, répteis, anfíbios e invertebrados. Em estudos ornitológicos, a jacurutu é frequentemente comparada ao bufo-real (Bubo bubo), uma espécie proximamente aparentada, que, apesar do tamanho notavelmente maior, ocupa o mesmo nicho ecológico na Eurásia, e ao búteo-de-cauda-vermelha (Buteo jamaicensis), com o qual frequentemente compartilha habitat, presas e hábitos de nidificação similares, sendo assim um equivalente ecológico durante o dia.[3] É uma das primeiras espécies a nidificar na América do Norte, pondo seus ovos semanas ou até meses antes de outras aves de rapina.[4]
A jacurutu tem uma coloração para camuflagem,[4] sendo geralmente clara com faixas marrons por baixo e marrom-manchada, geralmente com marcações pesadas, complexas e mais escuras por cima. Todas as subespécies apresentam barras escuras em certa medida ao longo dos lados.
Uma mancha branca de tamanho variável é vista na garganta, podendo continuar como uma listra que desce até o meio do peito até quando as aves não estão em exibição e que em indivíduos particularmente pálidos pode ser ampliada como uma grande área branca na barriga. A subespécie B. v. nacurutu, que ocorre no Brasil, costuma apresentar essa mancha em tamanho reduzido, muitas vezes invisível, ao menos quando em exibição, e raramente exibe a área branca do peito.[3] Variações individuais e regionais na coloração geral existem, com os indivíduos do subártico apresentando uma cor amarela desbotada, enquanto aqueles da costa do Pacífico das Américas do Norte, Central e de grande parte da do Sul podem ter cor marrom-escura coberta com manchas pretas. As pernas, embora quase totalmente obscurecidas por penas, são pretas. As penas nas pernas da jacurutu são as segundas maiores conhecidas em qualquer coruja (atrás apenas das da coruja-das-neves).[3] O bico, assim como as garras, é cinza-metálico.[5]
Todos os indivíduos da espécie têm um disco facial, que pode ter coloração avermelhada, marrom ou cinza (dependendo das variações geográfica e racial) e que é demarcado por um arco escuro.[6] Os "chifres" são tufos de penas de propósito não totalmente entendido, embora a teoria de que estes sirvam como pistas visuais em interações territoriais e sociossexuais com outras aves seja geralmente aceita.[3]
A jacurutu é a coruja mais pesada das Américas do Sul e Central e a segunda mais pesada da América do Norte, abaixo apenas da coruja-das-neves.[4][5] É robusta, com corpo em forma de barril, cabeça larga e asas grandes.[5] O tamanho pode variar consideravelmente através da distribuição geográfica, sendo as populações do interior do Alasca e Ontário maiores e as da Califórnia e do Texas menores, apesar de aquelas da Península de Yucatán e da Baixa Califórnia aparentarem ser ainda menores.[7][8] Os adultos chegam a medir de 43 a 64 cm de comprimento, sendo a média 55 cm, e 91 a 153 cm de envergadura de asas, sendo a média 122 cm. As fêmeas são um pouco maiores que os machos.[9][10] Em média, as fêmeas pesam 1608 g e os machos 1224 g.[11][12] Dependendo da subespécie, o peso máximo pode chegar a 2503 g.[13]
O comprimento da corda máxima é de 297-400 mm.[14] A carga alar, a razão entre o peso da ave e a área da asa, é alta, o que significa que as asas são pequenas em relação ao peso, sendo descrita como a proporcionalmente mais alta entre as aves de rapina.[6][15] A cauda é relativamente curta, como é típico da maioria das corujas, medindo de 175 a 252 mm de comprimento. Assim como outras corujas, a jacurutu é capaz de realizar um voo silencioso, o modo pelo qual as corujas, apesar de seus grandes tamanhos, voam sem fazer nenhum barulho discernível. Isso é possível graças a três componentes principais da estrutura das asas: a ponta das penas de suas asas ser serrilhada, o que ajuda a interromper a turbulência gerada pelo bater das asas; as penas mais macias ajudarem a amortecer o som; e, por fim, as bordas das penas acabarem de eliminar os sons emitidos. A estrutura da asa da jacurutu também lhe permite voar em velocidades muito baixas para o tamanho da espécie, tão devagar quanto 3 km/h quando está planando no vento.[16]
As pernas, os pés e as garras são grandes e poderosos. O tarso mede 54-80 mm.[5] A envergadura do pé, quando totalmente aberto, de garra a garra, é de aproximadamente 20 cm, comparado a 8 cm na coruja-pequena, 13-15 cm na coruja-das-torres e 18 cm na coruja-lapônica.[3][17] A jacurutu consegue aplicar ao menos 300 psis de força com suas garras, uma pressão consideravelmente maior do que a mão humana consegue exercer. Em algumas fêmeas grandes, o poder de preensão pode ser comparado ao de aves de rapina muito maiores, como a águia-real.[18]
O bico, duro e inflexível, mede 3,3-5,2 cm de comprimento, apesar de o cúlmen, a parte exposta do bico medida ao longo da parte superior do bico, medir 2,1-3,3 cm.[19]
As aberturas externas das orelhas, que estão ocultas por penas nas laterais da cabeça, são relativamente menores do que as do bufo-real, medindo 2,3 cm no eixo vertical, com a orelha esquerda sendo um pouco maior que a direita.[20] Essa assimetria, existente na maioria das espécies exclusivamente (ou quase exclusivamente) noturnas, permite a triangulação dos sons escutados quando a coruja caça à noite e é suficiente para que a ave consiga usar o tempo e a direção das ondas do som que chegam em cada orelha para localizar a presa com precisão, mesmo se esta estiver embaixo de alguma cobertura como neve. O formato de disco do rosto também ajuda a direcionar os sons que são ouvidos para as orelhas. Embora a verdadeira natureza/propósito dos tufos de orelha que estão presentes na jacurutu seja desconhecida, os pesquisadores concordam que eles não desempenham nenhum papel na capacidade auditiva da ave. Estima-se que sua audição seja até dez vezes maior que a de um ser humano.[21]
Os olhos da jacurutu, apenas um pouco menores que os dos humanos, são grandes até mesmo para uma coruja e estão, proporcionalmente, entre os maiores olhos de todos os vertebrados terrestres.[22] Essa espécie possui olhos cilíndricos que criam mais distância entre a lente do olhos e a retina, permitindo assim o funcionamento destes como uma lente objetiva para distâncias maiores comparado com o que é possível com olhos redondos.[23] Essa espécie tem os olhos altamente adaptados para a caça noturna, que proporcionam um amplo campo de visão, quase completamente binocular, uma grande superfície da córnea e uma retina predominantemente de haste.[24] Os olhos contêm hastes e cones, assim como na maioria das espécies que vê cores, mas a visão se assemelha muito à de muitas outras espécies noturnas. O comprimento de onda máximo observado pelos cones é de 555 nm e a pesquisa sugere que a jacurutu tenha fraca visão de cores, especialmente comparado a outras espécies de ave. Apesar do pior senso de visão de cores (ou talvez devido a isso), a espécie tem ótima visão noturna.[25] Ao invés de virar os olhos, uma coruja precisa virar a cabeça toda, e a jacurutu consegue girar a cabeça em 270°. A íris é amarela, exceto na subespécie nacurutu (da América do Sul), na qual é âmbar.
A combinação do porte, dos tufos de orelha proeminentes e da plumagem barrada da espécie distingue a jacurutu em grande parte de sua distribuição. Contudo, essa espécie pode ser facilmente confundida com Bubo magellanicus, com a qual pode haver sobreposição na área de ocorrência.[5] A última já foi considerada uma subespécie da primeira, mas atualmente é quase universalmente considerada uma espécie diferente, o que é apoiado pelo material genético, com a jacurutu sendo uma paraespécie.[5][6] A coloração geral é similar, mas B. magellanicus é notavelmente menor, com pés e cabeça menores, barras mais finas e mais numerosas por baixo, ao contrário das barras manchadas e irregulares de B. virginianus.[5] Outras espécies do gênero Bubo podem ser um pouco similares, mas a espécie é geralmente alopátrica, com exceção da coruja-das-neves durante o inverno. Espécies mais tropicais com tufos de penas nas orelhas, como o mocho-diabo (Asio stygius) e a coruja-orelhuda (A. clamator), são muito menores.[5] Outras corujas maiores não apresentam tufos de penas na orelha.[3]
A jacurutu é uma espécie do gênero Bubo, que pode incluir outras 25 espécies viventes, distribuídas predominantemente na África.[6] Essa coruja é uma das uma ou duas radiações do gênero através da Beríngia para a América. Considerando Bubo magellanicus uma divisão da jacurutu quando esta já havia se espalhado pelo continente, o consenso parece ser que a coruja-das-neves e a jacurutu já tinham se dividido na Eurásia e a primeira se espalhou em volta do Ártico pelo extremo norte da América do Norte, separadamente da última.[5][26] A jacurutu e o bufo-real podem ser coespecíficos, com base em semelhanças em história natural, distribuição geográfica e aparência.[3] Em um caso, um macho de jacurutu e uma fêmea de bufo-real em cativeiro produziram um híbrido aparentemente saudável.[27] Testes genéticos indicaram que a coruja-das-neves, não o bufo-real, é a espécie vivente mais proximamente aparentada.[5] Foram encontrados na América do Norte fósseis do Pleistoceno de corujas do gênero Bubo que podem ser ou de uma espécie diferente ou de uma paleosubespécie, que existiria desde o oeste das Montanhas Rochosas, sendo predominante nelas, para o leste até a Geórgia.[9][28] Quase todos os fósseis indicam que essas corujas eram maiores que as atuais.[29][30]
Uma grande quantidade de subespécies, mais de 20 ao todo, foram descritas. No entanto, muitas destas não são subespécies verdadeiras, mas apenas exemplos de variação individual ou clinal. As diferenças entre as subespécies são principalmente na coloração e no tamanho e geralmente seguem as regras de Gloger e de Bergmann.[9] As classificações mais conservadoras de subespécies da jacurutu descrevem tão pouco quanto 10,[5] apesar de um número intermediário ser típico na maioria.[9]
A jacurutu ocorre na maior parte das Américas do Norte e do Sul e muito irregularmente na América Central. Na porção mais austral da América do Sul, dá lugar à Bubo magellanicus, que ocupa todo o caminho para a Terra do Fogo, o extremo sul do continente. É ausente ou rara desde o sul de Guatemala, El Salvador, Nicarágua, e da Costa Rica ao Panamá (onde há apenas dois registros) e as florestas de mangue do noroeste da América do Sul. Também é ausente nas Índias Ocidentais, nas Ilhas da Rainha Carlota e em quase todas as ilhas das Américas, sendo assim a sua habilidade de colonizar ilhas aparentemente menor do que aquela da coruja-das-torres ou da mocho-dos-banhados.[3][32][34][43][44] Desde a sua divisão em duas espécies, é a segunda coruja mais amplamente distribuída das Américas, atrás apenas da coruja-das-torres.[5]
É uma das corujas ou até entre as aves mais adaptáveis do mundo quanto ao habitat, podendo fixar residência em árvores de vários tipos de vegetação, como florestas caducifólias, coníferas, decíduas temperadas e tropicais, pampas, pradarias, áreas montanhosas, desertos, tundra subártica, costas rochosas, mangues, e algumas áreas urbanas.[5] É menos comum nos lugares mais extremos das Américas. Nos desertos de Mojave e de Sonora, estão ausentes nas áreas mais secas e só são encontradas nas áreas vegetadas ou rochosas. Até na América do Norte, são raras em paisagens com mais de 70% de floresta primária, como nas florestas de faia das Montanhas Rochosas.[9][45] Foram registradas apenas poucas vezes em florestas tropicais como a Amazônia.[3] Nos Apalaches, aparentam usar a floresta primária,[46] mas no Arkansas são encontradas frequentemente próximas a aberturas agrícolas temporárias no meio de grandes áreas de floresta.[47] Assim como no centro-sul da Pensilvânia, usa terras agrícolas e pastagens mais do que coberturas totais de floresta decídua, indicando preferência por paisagens fragmentadas.[48] Em pradarias, campos e desertos, pode viver desde que existam cânions rochosos, ravinas íngremes e/ou barrancos arborizados com árvores que dão sombra para fornecer abrigo e locais de nidificação.[3][49]
Em áreas montanhosas da América do Norte, geralmente são ausentes acima da linha de árvores, mas podem ser encontradas até 2100 m na Califórnia e 3300 m nas Montanhas Rochosas.[3][50] Na Cordilheira dos Andes, por outro lado, adaptaram-se em uma espécie verdadeiramente montana, encontrada frequentemente a pelo menos 3300 m acima do nível do mar e são registradas regularmente na região sem árvores da puna entre os 4100 e 4500 m de altitude no Equador e no Peru.[51] São geralmente raras em habitats de pântanos sem marés,[52] e são substituídas na tundra ártica pela coruja-das-neves.[5] Prefere áreas onde habitats abertos (nos quais muitas vezes caça) e bosques (onde tende a se empoleirar e a nidificar) estão justapostos.[53][54][55] Assim, regiões rurais pouco povoadas podem ser ideais. Esta espécie pode ocasionalmente ser encontrada em áreas urbanas ou suburbanas. Contudo, nestes espaços ela aparenta preferir áreas com menos atividade humana e é mais provavelmente encontrada em configurações como parques, ao contrário das corujas Megascops asio e M. kennicottii, que podem ocorrer regularmente em ambientes suburbanos movimentados. Todas as jacurutus acasaladas são residentes permanentes de seus territórios, mas indivíduos solteiros e jovens movimentam-se livremente em busca de companhia e territórios, e deixam áreas com pouco alimento no inverno.[5]
Grande parte dos aspectos do comportamento da jacurutu é típico de outras corujas e da maioria das aves de rapina. Pela criação experimental de jovens em cativeiro, Paul L. Errington sentiu que esta era uma ave de "inteligência essencialmente baixa" que podia caçar apenas quando parcialmente selvagem e instintivamente movida pela fome para caçar a primeira presa que encontrasse. Ele mostrou que indivíduos em cativeiro que recebiam carne desde o nascimento, ao invés de terem que caçar ou simular uma caça para obter comida, não tinham essa capacidade.[56] Pelo contrário, William J. Baerg comparou suas jacurutus cativas criadas de modo comportamental a papagaios, aves famosamente inteligentes. Embora não sejam tão frequentemente brincalhonas, elas "conhecem seu guardião e geralmente aceitam tudo o que ele deseja fazer com uma boa dose de tolerância".[57] Arthur C. Bent também notou a variabilidade nos temperamentos de jacurutus quanto aos seus treinadores, algumas geralmente simpáticas, apesar da maioria ser eventualmente agressiva.[4] A maioria dos espécimes em cativeiro, uma vez maduros, parece ressentir-se com tentativas de contato e são frequentemente dados a atacar seus guardiões. Vão seguir pistas apenas se condicionadas desde jovens, mas raramente no mesmo nível de sucesso que é visto em algumas aves de rapina diurnas quando treinadas para falcoaria ou entretenimento, embora isso não esteja necessariamente relacionado à inteligência, como proposto por Errington.[56][57] Carl D. Marti também discorda das observações de Errington, notando que a sua seleção de presas não é "completamente aleatória como Errington sugeriu"; e sim "aparentando selecionar as suas presas mamíferas em relação geral com as populações destas. Coelhos-de-cauda-de-algodão parecem ser selecionados como presa em relação ao seu status populacional."[17]
Assim como a maioria das corujas, a jacurutu faz ótimo uso da discrição. Devido à sua plumagem de cor natural, camufla-se bem quando ativa à noite e quando descansa durante o dia. Durante o dia costuma descansar em árvores grandes (incluindo protuberâncias e grandes ocos, mas geralmente galhos grossos) mas pode ficar ocasionalmente em fendas ou pequenas cavernas em rochas ou arbustos densos. Pinheiros e outras coníferas podem ser preferidos quando estão disponíveis desde que particularmente densos e forneçam cobertura ao longo do ano. Tipicamente, os machos têm um poleiro não distante dos ninhos, algumas vezes usado por anos sucessivos.[58] Quando empoleiradas, estas aves podem descansar em uma posição na qual ficam eretas e o mais finas possível. O tipo de postura é conhecido como um método adicional de camuflagem para corujas, como a coruja-pequena e a coruja-lapônica, especialmente se humanos ou outros mamíferos potencialmente carnívoros se aproximam delas. O bufo-real assume essa posição raramente ou nunca.[59] Fora da temporada de nidificação, pode se empoleirar onde quer que seu trajeto de forrageamento termine ao amanhecer.[60] São geralmente ativas à noite, mas em alguns lugares podem ser ativas no fim da tarde ou no início da manhã. No crepúsculo, realiza algumas vocalizações antes de voar para um lugar mais aberto, isto é, um grande galho descoberto ou grandes pedras, para cantar. Normalmente são usados vários poleiros para marcar o território ocupado ou para atrair uma fêmea.[5] Apesar de sua camuflagem e de gostar de lugares ocultos, pode ser vista algumas vezes nos seus poleiros de passar o dia, principalmente por corvos-americanos (Corvus brachyrhynchos). Uma vez que estas corujas são, ao lado do búteo-de-cauda-vermelha, talvez a principal predadora de corvos e seus jovens, estes algumas vezes se juntam de uma distância considerável para atacar e grasnar para elas por horas a fio. Quando as corujas tentam voar para evitar este assédio, são muitas vezes perseguidas pelos corvos.[61]
As jacurutus são tipicamente sedentárias, frequentemente capazes de utilizarem um único território por toda a sua vida adulta.[62] Apesar de algumas espécies como a coruja-das-neves, a coruja-serra-afiada, a coruja-pequena e a mocho-dos-banhados serem verdadeiramente migratórias, a maioria das corujas norte-americanas não o são e costumar ser fiéis a um único território por todo o ano.[3] Os casais ocupam territórios por todo o ano e por um longo prazo. Os territórios são estabelecidos e mantidos por meio de vocalizações, com a maior atividade sendo antes da postura de ovos e no outono, quando os jovens dispersam, e podem medir em média de 2,1 km2 no Wyoming até 16 km2 em Yukon.[11][60]
A maior parte da defesa do território é realizada pelos machos, mas as fêmeas costumam ajudar seus parceiros em disputas de vocalização com vizinhos e intrusos, até mesmo durante a incubação.[9] Apesar de os limites do território serem mantidos com sucesso através apenas de vocalizações sem nem mesmo ver a coruja oponente, tais confrontos podem se tornar físicos, com vários níveis distintos de ameaça. O nível de ameaça mais alto envolve o abrir de asas, bater do bico, assobios, gritos agudos de longa duração, com o corpo em geral pronto para golpear o intruso com os pés. No caso de o intruso continuar confrontando, a coruja defensora dá um "salto" para a frente e atinge o oponente com os pés, tentando agarrá-lo com as garras.[9]
A territorialidade parece colocar um limite no número de pares reprodutores em uma determinada área. Indivíduos impedidos de estabelecer um território vivem uma existência silenciosa como "flutuadores". A radiotelemetria revelou que tais flutuadores se concentram ao longo dos limites de territórios já estabelecidos. No Lago Kluane, em Yukon, incursões em territórios vizinhos foram observadas apenas duas vezes — por fêmeas quando a fêmea vizinha morreu ou emigrou, o que sugere que a defesa do território pode ser específica do sexo. Pelo menos quatro indivíduos morreram em Kluane aparentemente mortas por outros de sua própria espécie em conflitos de território.[60] Corujas mortas por outras da mesma espécie são algumas vezes canibalizadas, embora a morte possa ter sido por causa de agressão por território.[63] As populações mais setentrionais irrompem ocasionalmente no sul durante épocas de escassez de alimentos,[64] mas não há migração anual até no limite norte da distribuição da espécie.[60]
O pico da atividade de caça tende a ser entre as 20:30 e a meia-noite e então pode retornar das 04:30 ao nascer do sol.[65] A caça também costuma ser mais prolongada durante o inverno devido à escassez de presas.[66] No entanto, a jacurutu pode aprender a ter uma certa presa como alvo durante a tarde quando esta estiver mais vulnerável, como o esquilo Sciurus niger enquanto constrói os seus ninhos e a iguana Sauromalus ater quando toma sol nas rochas do deserto.[67][68] Caça principalmente por meio da observação a partir de um poleiro alto. Durante as incursões de caça, costuma voar cerca de 50 a 100 m de poleiro a poleiro, parando para procurar alimento em cada um, até que percebam uma presa. A partir de tais pontos de vista, a coruja desce até o solo, frequentemente com as asas fechadas, para emboscar a presa.[5] A distância máxima de caça a partir de um poleiro elevado é de 90 m.[69] Devido às suas asas pequenas, mas amplas, essa espécie é adequada para baixa velocidade e capacidade de manobra.[15] Apesar de relatos de que não caça com as asas,[70] algumas vezes o faz voando baixo sobre aberturas no chão, procurando por atividade de presas.[5] Pode alcançar velocidades de mais de 65 km/h em voo nivelado.[3] Os voos para caça são devagar, muitas vezes bem acima do solo, onde a presa pode ocorrer em campo ou floresta abertos. O voo pairado breve (de aproximadamente 6–18 segundos) foi descrito, principalmente em áreas com vento.[71] Também pode ocasionalmente caçar andando no chão em perseguição a presas de pequeno porte ou, raramente, dentro de um galinheiro para atacar as aves dentro deste.[10] Roedores e invertebrados podem ser pegos a pé em torno da base de arbustos, através de áreas gramadas e perto de bueiros e outras estruturas humanas como fazendas.[9] Essa espécie não anda bem no solo: caminha como um estorninho, com uma maneira de andar lado-a-lado pronunciada. É conhecida por entrar em águas rasas para procurar presas aquáticas, embora isso tenha sido raramente relatado.[9] Pode apanhar aves e alguns mamíferos arbóreos diretamente dos galhos das árvores ou também em voo planado. As penas rígidas de suas asas permitem que produzam um som mínimo durante o voo.[2][5][10]
Quase todas as presas são mortas por esmagamento com os pés ou por serem incidentalmente apunhaladas com as garras, embora algumas também possam ser mordidos no rosto. A presa é engolida inteira quando possível e, quando isso acontece, a coruja regurgita plumadas com ossos e outros pedaços não-digeríveis aproximadamente 6 a 10 horas depois, geralmente no mesmo local onde a presa é consumida.[5] Essas plumadas são de cor cinza-escura ou marrom e muito grande, com 7,6 a 10,2 cm de comprimento e 3,8 cm de espessura, e são conhecidas por terem crânios de 3 cm de largura dentro delas.[10] Contudo, nem todas as presas podem ser engolidas de uma só vez, e desse modo as corujas voam com estas até um poleiro e arranca pedaços com o bico. A maioria dos estudos da dieta da espécie foca nas plumadas encontradas embaixo dos poleiros e ao redor dos ninhos, uma vez que estas proporcionam uma visão da diversidade das presas que são consumidas, mas restos da presa fora das plumadas podem fornecer pistas para presas excluídas destas. Assim, é recomendada uma combinação dos dois métodos.[3][72][73] Muitas presas de grande porte são desmembradas. A jacurutu pode tirar a cabeça de presas grandes antes de levá-las ao ninho ou ao poleiro onde vai consumi-la. As pernas também podem ser removidas, assim como as asas (em aves). Essa espécie também esmaga os ossos da presa para fazê-la mais compacta para carregar.[74] Ocasionalmente, as corujas podem retornar ao lugar da morte da presa e continuar a comê-la se esta for muito pesada para ser carregada em voo após o desmembramento.[4] Muitas corujas acumulam um esconderijo de presas, em especial aquelas que estão nidificando. Estes devem ser em um local seguro, geralmente uma forquilha em uma árvore alta. Nas regiões mais ao norte, onde presas maiores prevalecem, pode deixar o alimento que não foi consumido congelado e descongelá-lo mais tarde com o calor de seu próprio corpo.[6] O sucesso da caça parece necessitar de sub-bosque razoavelmente aberto, e testes experimentais de micro-habitat provaram que áreas abertas proporcionaram maior sucesso na caça de cinco espécies de roedor, com noites nubladas e folhagem de arbusto mais densa diminuindo-o.[75]
As presas podem variar muito, em função da oportunidade. De acordo com um autor, "quase qualquer criatura viva que anda, rasteja, voa ou nada, exceto os grandes mamíferos, é uma presa legítima da jacurutu".[18] Na verdade, a jacurutu tem o perfil de presas mais diverso entre todas as aves de rapina da América.[3] Já foram identificadas mais de 500 espécies predadas por esta coruja, com mais dúzias identificadas apenas o gênero ou aparência geral (especialmente numerosos invertebrados), e presumivelmente mais várias desconhecidas da sua população relativamente pouco estudada nos Neotrópicos. Mamíferos (mais de 200 espécies) e aves (em torno de 300 espécies) constituem a maior parte de sua dieta.[3][72] Sua dieta na América do Norte é constituída em 87,6% por mamíferos, 6,1% por aves, 1.6% por répteis e anfíbios e os 4,7% restantes por insetos, diversos outros invertebrados e peixes.[3] A massa estimada de cada presa da jacurutu vaeia de 0,4 g até 6,8 kg.[76][77] A maioria das presas está entre 4 g (musaranhos) e 2300 g (lebres).[76][78] Um único indivíduo necessita aproximadamente de 50 a 100 g de comida por dia e pode subsistir com uma grande caça por vários dias.[79] Apesar da grande diversidade de presas dessa espécie, na maior parte dos Estados Unidos Continentais, do leste ao meio-oeste, assim como no Canadá e no Alasca, vive em grande parte de poucas espécies: três lagomorfos - o coelho-da-flórida (Sylvilagus floridanus), a lebre-americana (Lepus americanus) e a lebre-da-califórnia (L. californicus); duas espécies de ratos do gênero Peromyscus: o rato-veadeiro (Peromyscus maniculatus) e P. leucopus; três espécies de rato-do-campo: o arganaz-do-campo (Microtus ochrogaster), M. pennsylvanicus e M. pinetorum e uma peste introduzida, o rato-marrom.[9][72][76]
A jacurutu é uma das aves da América do Norte que começa a sua reprodução mais cedo, aparentemente em parte por causa do longo anoitecer nesta época do ano e, adicionalmente, a vantagem competitiva que isso dá sobre outras aves de rapina. Na maior parte da América do Norte, o cortejo ocorre de outubro a dezembro e os casais são formados de dezembro até janeiro.[5] Pensava-se que esta espécie era estritamente monogâmica, mas análises recentes indicaram que um macho pode acasalar com duas fêmeas simultaneamente, como foi descoberto em Reno, Nevada, no ano de 2018.[80] Durante o cortejo no final do outono ou no início do inverno, o macho atrai a atenção de seu par vocalizando enfaticamente enquanto se inclina (com a cauda fechada ou aberta) e estufando a garganta branca para que esta pareça uma bola.[5] A garganta branca pode servir como um estímulo visual em condições de pouca luz típicas de quando o cortejo acontece.[60] O macho frequentemente voa para cima e para baixo em um poleiro, enquanto se aproxima de uma potencial parceira. Eventualmente, chega perto da fêmea e tenta esfregar o seu bico contra o dela enquanto se curva repetidamente. Se for receptiva, a fêmea vocaliza quando se encontra com o parceiro, mas é mais subjugada nos cantos e na exibição. O macho pode convencer a fêmea levando-a alimento fresco, que ambos compartilham.[4][5] Enquanto os machos costumam vocalizar enfaticamente por cerca de um mês ou seis semanas no final do ano, o período em que as fêmeas também vocalizam é geralmente de apenas uma semana a dez dias.[81] Os casais costumam procriar ano após ano e podem ficar juntos para o resto da vida, embora eles se associem uns com os outros mais livremente quando seus filhos se tornam independentes.[5] Pares que reacendem sua relação reprodutiva no inverno podem realizar um cortejo mais moderado para fortalecer os laços antes de produzir filhotes.[81]
O macho seleciona os locais de nidificação e chama a atenção das fêmeas para ele voando em sua direção e pisando nelas.[5] Devido ao grande tamanho desta ave, são preferidos ninhos abertos em vez de cercados com ramos circundantes. Assim como todas as corujas, a jacurutu não constrói o seu próprio ninho, tendendo a examinar a área em busca de um ninho abandonado, geralmente de aves de grande porte, como gaviões, e assume o controle para criar seus próprios filhos.[82] É a ave norte-americana que nidifica na maior variedade de habitats.[81] Muitos ninhos ficam em cavidades cavernosas de árvores mortas ou seus galhos, especialmente nos estados do sul dos Estados Unidos, em grandes árvores ao longo da borda de florestas primárias.[81] Em áreas montanhosas, especialmente em cânions do sudeste dos Estados Unidos e nas Montanhas Rochosas, saliências de penhascos, cavernas pequenas, e outras depressões protegidas podem ser usadas.[81] Quando vivendo em pradarias, na ausência de ninhos de outros animais, usando árvores ribeirinhas ou não nativas ou o solo descoberto de ocos de árvores ou estruturas feitas pelo homem, pedras, montículos, cortes de ferrovia, arbustos baixos e até mesmo o solo descoberto como locais de nidificação.[81] Ninhos no solo também foram registrados no meio de gramíneas altas na Flórida e de manchas de arbustos no solo do deserto.[3] Até as entradas das tocas de texugo-americano e de coiote são usadas como ninhos, apesar do risco inerente de compartilhar espaço com coabitantes potencialmente perigosos.[81] O comportamento de nidificação parece ter relação mais forte com a disponibilidade de presas do que como condições sazonais.[81] Há algumas evidências de que, se a disponibilidade de presas for baixa o suficiente, a espécie pode renunciar ao acasalamento a temporada inteira. Indivíduos de ambos os sexos já foram observados incubando os ovos assim que estes foram postos.[83]
A maioria dos ninhos em árvores usados pela jacurutu são construídos por outros animais, frequentemente entre os 4,5 e 22 m de altura. Ela costuma assumir o ninho usado por outra ave de grande porte, adicionando às vezes penas para forrar o ninho, mas geralmente não muito mais. Supostamente, há alguns casos em que o ninho foi reconstruído ou teve a sua estrutura reforçada, mas como regra nenhuma coruja jamais foi conhecida por realmente construir o ninho.[81] No sudoeste dos Estados Unidos também pode usar ninhos em cactos, construídos pelo gavião-asa-de-telha ou pelo búteo-de-cauda-vermelha, bem como grandes cavidades nestas plantas.[84] Os ninhos usados são frequentemente feitos por accipitrídeos de grande porte, desde espécies tão pequenas quanto o falcão-do-tanoeiro até a águia-careca e a águia-real, embora os mais frequentes sejam talvez os de búteos-de-cauda-vermelha e outros Buteoninae. Os segundos em popularidade são os de corvos (Corvus sp.). Além disso, já foram usados ninhos de ganso-do-canadá, savacu e garça-azul-grande, a última às vezes bem no meio de uma colônia ativa.[85][86] Os ninhos de folhas feitos por esquilos também são usados regularmente, mas são preferidos em geral ninhos de gravetos, uma vez que estes fornecem uma base muito mais firme e segura.[9]
A época do ano na qual os ovos são postos é variável na América do Norte. No sul da Flórida, a postura ocorre desde o final de novembro até o início de janeiro. No sudeste dos Estados Unidos, do sul do Texas até a Geórgia, desde o final de dezembro até o início de fevereiro. Do sul da Califórnia até o norte de Louisiana, desde o início de fevereiro até o final de março. O maior período é desde o final de fevereiro até o início de abril, na região do centro da Califórnia até a Carolina do Sul para o norte até Ohio e Massachusetts. Nas Montanhas Rochosas, no noroeste dos Estados Unidos, no norte da Nova Inglaterra e no leste do Canadá, a postura ocorre desde o início de março até o final de abril. No resto do Canadá e no Alasca, pode ocorrer do final de março até o início de maio.[81] A data mais tardia conhecida para a postura é em meados de junho em Saskatchewan e Yukon.[87] No noroeste de Utah e no centro-norte de Alberta, a postura pode acontecer 3–4 semanas mais cedo quando há abundância de alimento e o clima é favorável.[9] Em climas mais tropicais, as datas da temporada de reprodução são de algum modo indefinidas.[5] Geralmente há dois ovos por ninhada, podendo variar de um a seis (acima de três é incomum e acima de quatro é muito raro), dependendo de condições ambientais.[88][89] Um ovo mede em média 46,5 mm de largura, 55 mm de comprimento e pesa 51 g, embora a massa possa ser levemente mais alta em outros lugares, uma vez que este levantamento foi realizado no Condado de Los Angeles, na Califórnia, onde as corujas são relativamente pequenas.[90] A incubação dura entre 28 e 37 dias, sendo a média 33 dias.[91] A fêmea geralmente é a única responsável pela incubação e raramente sai do ninho, enquanto o macho caça e leva o alimento para ela, com a primeira entrega de comida à noite normalmente ocorrendo logo após o anoitecer.[9]
O filhote recém-nascido pesa em torno de 34,7 g e pode ganhar em média 33,3 g por dia nas primeiras quatro semanas de vida, com o peso típico com 25-29 dias sendo de 800 g nos machos e de 1000 g nas fêmeas.[90][91] Quando eclodem, os filhotes têm penugem cinza-esbranquiçada, com um pouco de marrom nas asas. Gradualmente, a plumagem aveludada juvenil passa pela penugem, sendo tipicamente uma amarelo-canela, mas com matizes variáveis, prevendo a eventual cor das corujas maduras. A extensão da penugem diminui gradualmente, desenvolvendo plumagem de aparência madura no final do verão, embora muitas aves do primeiro ano ainda tenham pedaços espalhados de penugem no outono. No final do outono, aves de primeiro ano têm aparência similar à dos adultos mas com um tom ligeiramente mais avermelhado, tufos de orelha menos desenvolvidos e uma mancha branca menor na garganta.[4] Os filhotes se desenvolvem principalmente no comportamento entre duas semanas e dois meses de idade, período em que adaptam a capacidade de se defender, agarrar alimentos e escalar. Vocalmente, os jovens são capazes de exercer sons fracos enquanto ainda está no ovo, que se desenvolvendo em um chiado rouco logo após a eclosão. Os chamados dos jovens aumentam rapidamente em intensidade, tom e características; alguns jovens do sexo masculino imitam a vocalização do pai no outono, mas geralmente concluem com várias notas gorgolejantes estranhas. O primeiro canto normal do juvenil não acontece antes de janeiro.[9][92] Os jovens mudam-se para galhos próximos às seis semanas e começam a voar cerca de uma semana depois. No entanto, geralmente não voam bem até que tenham em torno de 10 a 12 semanas de vida.[5] A idade na qual o juvenil sai do ninho é variável com base na abundância de alimento.[93]
Os jovens ficam em uma área entre 13,1 e 52 ha do ninho no outono, mas geralmente dispersam em milhares de hectares no final desta estação.[94][95] Os filhotes ainda pedem comida aos pais no final de outubro (cinco meses após saírem do ninho) e a maioria não deixa o território dos pais até pouco antes de os pais começarem a se reproduzir para a próxima ninhada (geralmente entre dezembro e janeiro).[96] Algumas aves podem não se reproduzir por um ano ou dois, e são frequentemente vagantes ("flutuadores") até que estabeleçam seus próprios territórios.[60] Com base no desenvolvimento da bursa, a jacurutu atinge a maturidade sexual aos dois anos de idade.[97]
Muitos tribos guerreiras nativas dos Estados Unidos admiravam a jacurutu por sua "força, coragem e beleza".[79] Os Pima, povo do sudoeste dos Estados Unidos acreditavam que esta coruja era a reencarnação de guerreiros mortos que voam à noite. Os Arikara das Grandes Planícies tinham uma sociedade mística na qual os iniciados eram obrigados a adornar máscaras faciais feitas de penas da cauda e da asa da jacurutu. Algumas nações indígenas consideravam a jacurutu um espírito amigável que poderia ajudar em questões amorosas, como os Passamaquoddy do Maine, que pensavam que o chamado desta espécie era uma flauta mágica do amor projetada para inflamar as paixões humanas. Os Hopis, do sudoeste dos Estados Unidos, também associaram essa coruja com a fertilidade, embora de um tipo diferente: eles acreditavam que a vocalização desta coruja no verão previa um clima quente, o que produzia boas safras de pêssego. Durante o solstício de inverno, este povo realizava uma cerimônia com penas de jacurutu na esperança de convocar o calor do verão. Tribos do Novo México são conhecidas por usar as penas das asas da jacurutu para produzir flechas que podiam atingir seus inimigos com um mínimo de som. Os Zuni seguravam as penas da coruja em suas bocas na esperança de obter um pouco do silêncio que as corujas usam em emboscadas enquanto atacavam seus inimigos de outras tribos. Os Iroqueses pensavam que a origem da jacurutu era devido a uma coruja imatura que irritava Raweno, o criador todo-poderoso, enquanto este criava os coelhos, fazendo este deixar a coruja "coberta de lama" (camuflagem escura) e condenada a ter uma incessante vocalização de "whoo-whoo", que usava para assediar Raweno à noite, porque este era ativo durante o dia.[79]
A jacurutu é a ave provincial de Alberta, no Canadá.[98]
A jacurutu (Bubo virginianus), também conhecida como corujão-orelhudo, jucurutu, mocho-orelhudo ou corujão-da-virgínia, é uma coruja de grande porte nativa das Américas. É uma ave extremamente adaptável com uma vasta distribuição, sendo a mais amplamente distribuída do continente. Sua alimentação consiste em coelhos e lebres e ratos, apesar de caçar livremente qualquer animal que consiga, incluindo roedores e outros pequenos mamíferos, mamíferos de médio porte, aves, répteis, anfíbios e invertebrados. Em estudos ornitológicos, a jacurutu é frequentemente comparada ao bufo-real (Bubo bubo), uma espécie proximamente aparentada, que, apesar do tamanho notavelmente maior, ocupa o mesmo nicho ecológico na Eurásia, e ao búteo-de-cauda-vermelha (Buteo jamaicensis), com o qual frequentemente compartilha habitat, presas e hábitos de nidificação similares, sendo assim um equivalente ecológico durante o dia. É uma das primeiras espécies a nidificar na América do Norte, pondo seus ovos semanas ou até meses antes de outras aves de rapina.
Výr bielobradý alebo výr západný, výr virgínsky (lat. Bubo virginianus) je najväčšia a zrejme aj najsilnejšia americká sova vyskytuje sa v Severnej, Strednej a Južnej Ameriky – od severnej hranice rozšírenia lesa až po Patagóniu.
Výr bielobradý meria v dĺžke 51 – 60 cm a váži 900 – 1 500 g. Výr bielobradý má hrdzavohnedé očné disky a čierny zobák, žltočierne perové ušká a svetlohnedé líca, perie okolo zobáka je šedé. Pod zobákom na mieste brady má biele perie a na hrudi má tmavohnedé škvrny na bielom perí. Na bielom chvoste je päť čiernych pruhov a nohy má bielej farby. Má rozpätie krídel 101 – 153 cm. Hlava meria 20 cm. Výr, ako všetky ostatné sovy, má dobrý ostrý zrak. Na nohách má 4 pazúre. Na lebke má výr bielobradý dve veľké očné jamky a veľký zobák. Kostra dolných končatín a kostra krídel sú väčšie. Výr bielobradý, ako aj niektoré iné sovy, má výrazné perové ušká. Ich presný význam nie je známy. Podľa niektorých odborníkov slúžia na „rozbitie“ tvaru sovy – čiže na jeho maskovanie. Podľa iných sú určené na vnútrodruhovú komunikáciu a druhové rozpoznávanie. Faktom je, že perové ušká nijako nesúvisia so sluchom.
Výr bielobradý nie je špecializovaný na hniezdisko. Hniezdi na skalných stenách a na starých budovách s úkrytmi. Živí sa menšími cicavcami, obojživelníkmi, plazmi (mladými aligátormi severoamerickými), rybami a kôrovcami. Je aktívny najmä v noci. Samica nakladie 1 – 5 vajec o ktoré sa starajú obidvaja rodičia. Rodičia sa starajú o mláďa ešte aj 6 týždňov po tom, čo mláďa opustí hniezdo. Mláďa má funkčné perie už od dvoch mesiacov. Rodičia si potomstvo srdnato bránia – sú známe prípady, keď účinne zabránili prístupu k mláďatám aj človeku.
Výr bielobradý alebo výr západný, výr virgínsky (lat. Bubo virginianus) je najväčšia a zrejme aj najsilnejšia americká sova vyskytuje sa v Severnej, Strednej a Južnej Ameriky – od severnej hranice rozšírenia lesa až po Patagóniu.
Virginiauv[2] (Bubo virginianus) är en amerikansk uggla som tillhör släktet Bubo.[3] Den är nästan lika stor som berguven. Arten är aldrig sedd i västra palearktis. Möjligen kan parkrymlingar förekomma.
Virginiauven är en stor fågel, med en längd på mellan 46 och 63 centimeter (honan är störst) och en vingspann mellan 101 och 145 centimeter. Vikten ligger mellan 0,9 och 2,5 kilogram.[4] Den har stora örontofsar, gula ögon och en fjäderdräkt som är spräcklig i brunt, grått och svart upptill med vit strupfläck; buken är ljusare med bruna tvärstreck.[5]
Den finns i många miljöer, från skogar, öknar och även bebodda områden. Den tenderar dock att föredra öppen terräng som ängar och odlade fält.[4]
Virginiauven, som jagar på natten, tar ett flertal byten, framför allt mindre däggdjur (det är en av de få djur som tar skunkar) och fåglar (även rovlevande fåglar som andra ugglor, pilgrimsfalk och fiskgjusar), men även reptiler, groddjur och ryggradslösa djur.[4]
Den bygger inget eget bo, utan föredrar att ta över andra fåglars reden. Den är inte särskilt noga med placeringen; boet kan finnas i träd, klippskrevor, ihåliga träd, byggnader eller på marken.[4] Honan lägger en till fem vita, nästan klotrunda ägg[4], som ruvas i mellan 4 och 5 veckor. Ungarna blir flygga efter fem veckor.[5]
Virginiauven förekommer i Nordamerika, Centralamerika och norra Sydamerika. Den delas in i hela 14 underarter med följande utbredning.[3]
Magellanuven (B. magellanicus) behandlas ofta som underart till virginiauven.[6]
Enligt IUCN är den inte hotad (livskraftig, LC)[1]. Den är emellertid själv en fara för hotade arter som pilgrimsfalk[4].
Virginiauv (Bubo virginianus) är en amerikansk uggla som tillhör släktet Bubo. Den är nästan lika stor som berguven. Arten är aldrig sedd i västra palearktis. Möjligen kan parkrymlingar förekomma.
Amerika puhusu (Bubo virginianus), baykuşgiller (Strigidae) familyasından, Kuzey Amerika'da yaşayan puhu cinsinden iri bir baykuş türü.
43–64 cm uzunluğunda, 91–153 cm kanat genişliğindedir[1][2][3][4]. Dişiler erkeklerden daha büyüktür. Ortalama olarak bir yetişkin 52 cm uzunluğa, 124 cm kanat genişliğine ve 1.4 kg ağırlığa sahiptir[5].
Çoğunlukla, tavşan gibi ortaboy ya da fare, sincap, lemming gibi küçük memelilerle beslenirler[3][4]. Düzenli olarak yediği diğer memliler arasında sivri fare, yarasa, tatu, misk sıçanı, sansar ve gelincik bulunur[3][4].
Amerika puhusu (Bubo virginianus), baykuşgiller (Strigidae) familyasından, Kuzey Amerika'da yaşayan puhu cinsinden iri bir baykuş türü.
Cú sừng, tên khoa học Bubo virginianus, là một loài chim trong họ Strigidae.[2]
Nhiều phân loài của loài này đã được đặt tên, chúng khác nhau chủ yếu về màu sắc và kích thước và nhìn chung chúng tuân theo quy tắc của Gloger và Bergmann:[3]
Cú sừng lớn Bắc Mỹ (B. v. subarcticus) ở Manitoba
Cú sừng lớn California (B. v. pacificus), Bernal Hill Park, San Francisco
Bubo virginianus (Gmelin, 1788)
Ареал Охранный статусВирги́нский фи́лин[1] (Bubo virginianus) — хищник из семейства совиных или настоящих сов, широко распространён на территориях обеих Америк. Встречается как в лесах, так и в степях и пустынных зонах. Является самым крупным представителем сов в Новом Свете и вторым по счёту в мире в целом (после филина евроазиатского).
Впервые был замечен на территории колонии Виргиния, по имени которой и был назван. Окраска у него преимущественно от рыжевато-бурой до серой, чёрной или белой. Размах его крыльев достигает 1,5 метров. У птиц, живущих в тундре и пустыне, преобладает более светлый окрас, а у тех, кто живёт в лесах, — более тёмный. На голове у него есть перьевые «ушки», за что его прозвали «большим рогатым филином». Снизу у него окрас перьев более светлый, с темными разводами и пересекающими белыми полосами.
У филинов большие оранжево-жёлтые глаза. У некоторых видов имеется пуховая кайма, обрамляющая лицевую часть головы. Молодые особи по внешнему виду похожи на взрослых. Самки в среднем крупнее самцов на 10—20 %. Длина тела взрослой птицы около 46—63,5 см, а размах крыльев 91—152 см. Масса взрослых особей от 900 до 1800 грамм.
Виргинские филины издают глухие гудящие звуки, также они могут издавать громкие визги, урчание и короткие звуки, похожие на звуки кашля.
Виргинский филин распространён практически по всей территории Северной Америки, за исключением Крайнего Севера. Встретить его можно практически везде: в лесах, степях, пустынях и сельскохозяйственных землях. Встречается и в городских парках. Является оседлым, но птицы северных территорий могут откочёвывать к югу зимой. В Южной Америке встречается в предгорьях Анд и в зоне редколесий, а также в некоторых других местах. Ареал не выходит за пределы Америки.
Гнездится в дуплах или брошенных гнёздах других птиц. Может гнездиться в домах, расселинах скал и даже пещерах. Иногда гнездится на земле.
Виргинские филины преимущественно ведут ночной образ жизни и активны ночью. Зимой ведут одиночный образ жизни, летом же собираются в пары. Члены семьи филинов держатся вместе до осени, после чего молодняк улетает. Предпочитают одиночный образ жизни, собираясь в пары в период размножения.
Брачный период начинается в январе-феврале. Во время брачного периода самцы активно призывают пением самок, которые иногда присоединяются к пению. Филины очень агрессивны при защите гнезда и атакуют врага, пока не убьют или не изгонят его. Самка откладывает 2—4 яйца с промежутком в два-три дня в апреле-мае. Насиживание яиц осуществляется только самкой и обычно длится около 32 суток. Птенцы филина начинают покидать гнездо на 5—7 неделе, способности к полёту приобретают к 9—10 неделе. Растут преимущественно медленно. Выкармливание птенцов длится несколько недель.
Виргинские филины предпочитают охоту из засады и атакуя с воздуха. Рацион филинов богат и включает около 253 видов животных и птиц, однако отдаёт предпочтение грызунам. За раз способен унести добычу в 2—3 раза превосходящую свой собственный вес. Нападает на птичники, воруя цыплят. Мелкую добычу глотает целиком, более же крупную расчленяет. Известно, что это единственный хищник, который способен на охоту за скунсовыми.
Вирги́нский фи́лин (Bubo virginianus) — хищник из семейства совиных или настоящих сов, широко распространён на территориях обеих Америк. Встречается как в лесах, так и в степях и пустынных зонах. Является самым крупным представителем сов в Новом Свете и вторым по счёту в мире в целом (после филина евроазиатского).
大雕鴞(學名:Bubo virginianus)是美洲一種大型的貓頭鷹。牠們的適應力強,是美洲分佈得最廣的鴟鴞科。
大雕鴞長46-68厘米,翼展長101-153厘米。雌鳥比雄鳥大,平均長55厘米,翼展長124厘米,重1.4公斤。較大的個體分佈在近極地,較小的個體則接近赤道,符合伯格曼定律(Bergmann's Rule)。
大雕鴞的耳邊絨毛很大,面部呈紅色、褐色或灰色,喉嚨有一片白色。虹膜黃色,其下B. V. nacurutu的虹膜則是琥珀色。其「角」並非耳朵或是真正的角,而只是絨毛或羽毛。下身淺色帶有褐色斑紋。腳上至爪前都長有羽毛。個別及地區性的顏色都有分別:靠近極地的個體呈較淺色,而在中美洲的則呈深朱古力褐色。
大雕鴞的叫聲是低音但大部的咕咕聲,一連四或五個音節。雌鳥的叫聲較高音,尾音上升。幼鳥只會發出嘶嘶聲,很易與倉鴞的叫聲混淆。
大雕鴞很易與小雕鴞及其他雕鴞屬混淆。不過牠們一般都是異域的。
大雕鴞之下命名了很多亞種,但是其中很多都是一些個體或漸變群。亞種的分別主要是在毛色及大小,而且一般都符合格洛格尔律或伯格曼定律:[2][3]
牠們呈深灰色,有很多斑紋。腳呈淡色及狼斑紋。
加利福尼亞州發現的古新世Bubo sinclairi可能是大雕鴞的古亞種。[5]
大雕鴞分佈在北美洲的亞北區經中美洲及南美洲南至火地群島。在瓜地馬拉南部、薩爾瓦多及尼加拉瓜至巴哈馬、亞馬遜森林及南美洲南部、與及西印度群島及大部份海島上都不會見到大雕鴞。[3][6]
大雕鴞會棲息在樹上,包括落葉林、針葉林、混交林、熱帶雨林、潘帕平原、大草原、山區、沙漠、亞北區的凍土層、石灘、紅樹林及一些市區。牠們較少出沒在極端氣候的地區,並不會到濕地環境[7]及高海拔的凍土層。所有已交配的大雕鴞都是留鳥,未交配的或幼鳥就會在較少食物供應的冬天離開,到處尋找伴侶及地盤。
大雕鴞的鳥蛋及雛鳥是狐狸、郊狼或野貓的獵物。成鳥並沒有天敵,但與鷹、雪鴞及其他大雕鴞對抗時可能會被殺死。牠們並非受到威脅的生物。[1]
大雕鴞有雙目視覺,可以準確尋找獵物及在低光度下仍能看見。牠們的眼睛大如人類的,但卻不能在眼窩內轉動。所以大雕鴞會轉動頭部。其頸部在身體保持不動時可以轉動達270°。
大雕鴞的聽覺也很好。牠們感覺深度的能力比人類更強。這是由於牠們的耳朵並非在頭的兩側,而是在頭較高的位置。只要傾斜或轉動頭部,牠們就可以準確測量聲音的橫向及直向位置。
大雕鴞是在夜間獵食,會站在高處等待獵物,再俯衝擒獲獵物。牠們主要狩獵細小至中等的哺乳動物,如野兔、兔、浣熊、大家鼠、松鼠、小鼠屬、鼴科、田鼠、旱獺、鼩鼱科、蝙蝠、犰狳科、鼬屬及沙鼠。牠們更是豪豬及鼬鼠的天敵。牠們也會獵食其他鳥類,由細小的戴菊鳥至大如大藍鷺不等。涉禽(尤其是蹼雞屬及鴨),甚至乎猛禽的雪鴞都會被獵食。牠們有時會吃農場的雞及狗。牠們卻只會有時吃爬行類、兩棲類、魚類、甲殼類及昆蟲。也有紀錄牠們會同類相食。
大雕鴞爪的壓力可以達到每平方吋500磅,遠遠超過人手的60磅的握力。在北部若有較大的獵物,牠們會將吃剩的獵物冰凍起來,到有需要時再用體溫來解凍。牠們傾向在同一地方反芻食物。
大雕鴞是北美洲最早繁殖的鳥類。牠們於1月下旬或2月初繁殖,在10月的冬天就開始互相呼叫。牠們會在12月前交配。位於熱帶氣候的群落,其繁殖季節很不明確。牠們會接管其他大至鳥類的鳥巢,有時更會加些羽毛。烏鴉及渡鴉、紅尾鵟或大型松鼠的巢都是牠們的對象。牠們有時也會利用樹洞、崖壁、空置大廈及人工平台等作為鳥巢。
大雕鴞每次平均會生2隻蛋,介乎1-5隻蛋。鳥蛋平均闊4.65厘米,長5.52厘米,重51克。孵化期介乎30-37日,平均33日。雙親會不斷哺育雛鳥至兩星期大,隨後開始減少。6星期大的幼鳥會移到附近的樹枝,1星期後開始學飛。雛鳥在10月下旬仍會要求哺育及未離開雙親,直至12月雙親開始繁殖第二胎。幼鳥會有1-2年時間的交配空白期,這段時間牠們會流浪,直至牠們交配及建立自己的地盤。
アメリカワシミミズク(亜米利加鷲木莵、学名:Bubo virginianus)英名グレイトホーンアウル(大きい角のふくろう)は、フクロウ目フクロウ科に分類される鳥類の一種。
など
森林や農耕地に生息する。夜行性。タカやカラスの古巣、樹洞で子育てをする。
食性は肉食性で、小型の哺乳類、鳥類、爬虫類、両生類、魚類、昆虫類を捕食する。
アメリカワシミミズク(亜米利加鷲木莵、学名:Bubo virginianus)英名グレイトホーンアウル(大きい角のふくろう)は、フクロウ目フクロウ科に分類される鳥類の一種。
やや緊張した状態 閉眼したアメリカワシミミズク