Tachycineta bicolor (Vieillot 1808)

L'oreneta bicolor^[1] (Tachycineta bicolor) és un ocell de la família dels hirundínids (Hirundinidae) que habita terrenys amb vegetació poc alta i sovint a prop de l'aigua des de l'oest d'Alaska i la major part del Canadà fora de les zones més septentrionals, fins a Califòrnia, Nevada, Arizona, Louisiana, Mississipí, Geòrgia i Carolina del Nord. Passa l'hivern a Mèxic i l'Amèrica Central.

Referències

Aderyn a rhywogaeth o adar yw Gwennol coed America (sy'n enw benywaidd; enw lluosog: gwenoliaid coed America) a adnabyddir hefyd gyda'i enw gwyddonol Tachycineta bicolor; yr enw Saesneg arno yw Tree swallow. Mae'n perthyn i deulu'r Gwenoliaid (Lladin: Hirundinidae) sydd yn urdd y Passeriformes.^[1] Dyma aderyn sydd i'w gael yng ngwledydd Prydain, ond nid yng Nghymru.

Talfyrir yr enw Lladin yn aml yn T. bicolor, sef enw'r rhywogaeth.^[2] Mae'r rhywogaeth hon i'w chanfod yn Ne America a Gogledd America.

Teulu

Mae'r gwennol coed America yn perthyn i deulu'r Gwenoliaid (Lladin: Hirundinidae). Dyma rai o aelodau eraill y teulu:

Rhestr Wicidata:

Gweler hefyd

• Rhestr Goch yr IUCN

Cyfeiriadau

Sumpfschwalbe im Flug

Die Sumpfschwalbe (Tachycineta bicolor) ist ein Singvogel, der im Norden Nordamerikas brütet und in Mexiko, Zentralamerika und der Karibik überwintert.

Merkmale

Die Sumpfschwalbe erreicht eine Körperlänge von gut 14 bis 15 Zentimeter sowie ein Gewicht von 18 bis 22 Gramm.^[1] Die Geschlechter weisen weder in der Größe noch in der Gefiederfärbung einen Geschlechtsdimorphismus auf. Der Kopf, das Rückengefieder sowie die Flügel sind überwiegend dunkelblau bis blauschwarz gefärbt. Die Kehle, die Brust und die Bauchseite ist weißlich gefärbt. Das bläuliche Gefieder schimmert bei Lichteinfall metallisch. Die Unterseite der Flügel ist hellbraun gefärbt. Die Außenfahnen der Flügel sind meist schwarz gefärbt. Im Bereich der Augen zeigt sich eine schwarze Augenbinde. Die langen Flügel reichen bis über den Schwanz hinaus. Die Beine sind recht kurz. Das Gleiche gilt auch für die Zehen. Beides ist ein Indiz für die fehlende Bewegung auf dem Erdboden. Extremitäten und Zehen sind bräunlich gefärbt. Der Schnabel weist eine schwarze Färbung auf. Die Jungvögel ähneln in der Gefiederfärbung den erwachsenen Vögeln. Nur die bläulichen Gefiederteile sind teilweise bräunlich.

Verbreitung

Die Sumpfschwalbe ist eine nearktische Art. Sie brütet in Alaska, im zentralen Yukon (Territorium) und im Northwest Territories, an den südlichen Ufern der Hudson Bay sowie im Süden von Quebec und im Osten Labradors.^[2] Sie ist ein obligatorischer Zugvogel, die in den Süden der Vereinigten Staaten, nach Mexiko und die Ostküste Zentralamerikas zieht.

Lebensweise

Ei, Sammlung Museum Wiesbaden

Der Vogel, der oft in großen Trupps auftritt, fängt Insekten im Flug. Daneben ernährt er sich von Beeren, darunter Lorbeerfrüchte, die nur wenige Vogelarten verdauen können.

Das Brutpaar baut in künstlichen oder natürlichen Höhlen in der Nähe des Wassers ein napfförmiges Nest aus pflanzlichen Material. Vier bis sechs Eier werden von Weibchen 15 Tage lang bebrütet. Nach 16–30 Tagen werden die Jungvögel flügge.

Belege

Literatur

• Bryan Richard: Vögel. Parragon, Bath, ISBN 1-40545-506-3
• Richard Sale: A Complete Guide to Arctic Wildlife, Verlag Christopher Helm, London 2006, ISBN 0-7136-7039-8

Einzelbelege

1. ↑ Sale, S. 290
2. ↑ Sale, S. 290

The tree swallow (Tachycineta bicolor) is a migratory bird of the family Hirundinidae. Found in the Americas, the tree swallow was first described in 1807 by French ornithologist Louis Vieillot as Hirundo bicolor. It has since been moved to its current genus, Tachycineta, within which its phylogenetic placement is debated. The tree swallow has glossy blue-green upperparts, with the exception of the blackish wings and tail, and white underparts. The bill is black, the eyes dark brown, and the legs and feet pale brown. The female is generally duller than the male, and the first-year female has mostly brown upperparts, with some blue feathers. Juveniles have brown upperparts, and grey-brown-washed breasts. The tree swallow breeds in the US and Canada. It winters along southern US coasts south, along the Gulf Coast, to Panama and the northwestern coast of South America, and in the West Indies.

The tree swallow nests either in isolated pairs or loose groups, in both natural and artificial cavities. Breeding can start as soon as early May, although this date is occurring earlier because of climate change, and it can end as late as July. This bird is generally socially monogamous (although about 8% of males are polygynous), with high levels of extra-pair paternity. This can benefit the male, but since the female controls copulation, the lack of resolution on how this behaviour benefits females makes the high level of extra-pair paternity puzzling. The female incubates the clutch of two to eight (but usually four to seven) pure white eggs for around 14 to 15 days. The chicks hatch slightly asynchronously, allowing the female to prioritize which chicks to feed in times of food shortage. They generally fledge about 18 to 22 days after hatching. The tree swallow is sometimes considered a model organism, due to the large amount of research done on it.

An aerial insectivore, the tree swallow forages both alone and in groups, eating mostly insects, in addition to molluscs, spiders, and fruit. The nestlings, like the adult, primarily eat insects, fed to it by both sexes. This swallow is vulnerable to parasites, but, when on nestlings, these do little damage. The effect of disease can become stronger as a tree swallow gets older, as some parts of the immune system decline with age. Acquired T cell-mediated immunity, for example, decreases with age, whereas both innate and acquired humoral immunity do not. Because of its large range and stable population, the tree swallow is considered to be least concern by the International Union for Conservation of Nature. In the US, it is protected by the Migratory Bird Treaty Act of 1918, and in Canada by the Migratory Birds Convention Act. This swallow is negatively affected by human activities, such as the clearing of forests; acidified lakes can force a breeding tree swallow to go long distances to find calcium-rich food items to feed to its chicks.

Taxonomy and etymology

The tree swallow was described as Hirundo bicolor by Louis Pierre Vieillot in his Histoire naturelle des oiseaux de l'Amérique Septentrionale, published in 1807.^[2] It was then placed in its current genus Tachycineta when Jean Cabanis established it in 1850.^[3] In 1878, Elliott Coues suggested that the tree swallow, at the very least, be put in its own subgenus, Iridoprocne, on the basis of its plumage, along with the white-winged swallow, Chilean swallow, white-rumped swallow, and mangrove swallow.^[4] By 1882, he had upgraded this to a full genus.^[5] Some authors continued to use this classification, with the addition of Tumbes swallow; however, genetic evidence supports the existence of a single genus, Tachycineta.^[6] The tree swallow is also called the white-bellied swallow for its white underparts.^[7]

The generally accepted genus name is from Ancient Greek takhykinetos, "moving quickly", and the specific bicolor is Latin and means "two-coloured".^[8] The other genus name, Iridoprocne, comes from the Greek iris, meaning rainbow, and Procne, a figure who supposedly turned into a swallow.^[5]

How exactly the tree swallow is related to other members of Tachycineta is unresolved. In studies based on mitochondrial DNA, it was placed basal (meaning it was the first offshoot in the species tree) within the North American-Caribbean clade consisting of the violet-green swallow, golden swallow, and Bahama swallow.^[9][10] Although mitochondrial DNA is advocated as a better indicator of evolutionary changes because it evolves quickly, analyses based on it can suffer because it is only inherited from the mother, making it worse than nuclear DNA from multiple loci at representing the phylogeny of a whole group.^[11] A study based on such nuclear DNA placed the tree swallow in the most basal position within Tachycineta as a whole (as a sister group to the rest of the genus).^[12]

Description

A juvenile tree swallow

The tree swallow has a length between about 12 and 14 cm (4.7 and 5.5 in) and a weight of approximately 17 to 25.5 g (0.60 to 0.90 oz). Wingspan ranges from 30 to 35 cm (12 to 14 in).^[13] The male has mostly glossy blue-green upperparts, the wings and tail being blackish. The underparts^[14] and the cheek patch are white,^[7] although the underwing coverts are grey-brown.^[14] The bill is black, the eyes dark brown, and the legs and feet pale brown.^[7] The female is duller in colour than the male, and sometimes has a brown forehead.^[14] The second-year^{[note 1]} female also has brown upperparts, with a variable number of blue feathers; some third-year females also retain a portion of this subadult plumage.^[15] According to a 1987 study, this likely allows a younger female to explore nest sites, as the resident male is usually less aggressive to a subadult female.^[16] A 2013 study found that the resident female was less aggressive towards second-year female models when they were presented separately from older models. Why the female eventually replaces its subadult plumage is unknown; it may allow males to assess female quality, as pairs mate assortatively based on plumage brightness.^[17] The juvenile tree swallow can be distinguished by its brown upperparts and grey-brown-washed breast.^[14]

Voice

Two tree swallows singing

The tree swallow's song consists of three parts: the chirp, the whine, and the gurgle. These sections may be repeated or omitted, and all can stand alone. The first, as the chirp call (sometimes divided into the contact call and solicitation call), is made by the female during copulation^[18] and in both sexes to stimulate the nestlings to beg^[19] or (in some populations) when their mate leaves or enters the nest cavity. The whine, generally consisting of a downward shift in frequency followed by an upward shift, may be given alone as the anxiety call,^[18] occasionally made in response to certain predators.^[20] The gurgle, as when it appears at the end of the song, is usually uttered twice. It is likely involved in pair bonding. The chatter call is used to advertise nest sites (the reason it is also known as the "nest-site advertising call") and is also given to intruding conspecifics. A short high-pitched submission call is sometimes uttered after an aggressive encounter with another tree swallow. While being physically restrained or in pain, a distress call may be given. The male often utters a ticking (or rasping) aggression call during copulation, and both sexes use it at the end of mobbing dives. The alarm call is given in reaction to predators and other intruders,^[18] and can serve to induce older nestlings to crouch and stop begging when a predator is near.^[21]

Communication between parents and offspring can be disrupted by human-generated noise. A 2014 study, for example, found that broods for whom white noise was played were less likely to crouch or stop begging in response to alarm calls. Parents did not alter their calls to compensate, likely increasing predation risk.^[22] Noise can also disrupt whether parents respond to begging, but this may be balanced out by the louder calls nestlings give when exposed to it. Increased begging effort, however, may be ineffective or costly for louder levels of noise.^[23]

Distribution and habitat

The tree swallow breeds in North America. Its range extends to north-central Alaska and up to the tree line in Canada. It is found as far south as Tennessee in the eastern part of its range, California and New Mexico in the west, and Kansas in the centre. It occasionally breeds further south in the US,^[7] and vagrants are sometimes found in the Arctic Circle, the northern Pacific, Greenland, and Europe.^[14] The wintering range is from California and southwestern Arizona in the west and southeastern Virginia in the east south along the Gulf Coast to the West Indies, Panama, and the northwestern South American coast.^[7] While migrating, this swallow often uses stop-over sites, spending an average of 57 days at these areas during autumn. To get to its wintering range, it often uses one of three flyways: the Western flyway, west of the Rocky Mountains; the Central flyway, between the Rocky Mountains and the Great Lakes, stretching south into Eastern Mexico; and the Eastern flyway, from the Great Lakes east.^[24] When a swallow returns to nest, it usually does not change breeding sites.^[25]

The breeding habitat of this bird is primarily in open and wooded areas, especially those near water.^[7] It roosts every night during the non-breeding season, preferring to rest in cane or reed beds over water, but it is also found over land and on trees and wires. Roosting sites are generally 100 to 150 kilometres (62 to 93 mi) apart.^[26]

Behaviour

Tree swallows fighting

Because of the large amount of research on the tree swallow and how it willingly breeds in nest boxes, biologist Jason Jones recommended that it be considered a model organism.^[27] Although it is aggressive during the breeding season, this swallow is sociable outside of it, forming flocks sometimes numbering thousands of birds.^[7]

Breeding

A natural nest hole

The tree swallow nests in structures with pre-existing holes, both natural and artificial. These were once found only in forested regions, but the building of nest boxes has allowed this bird to expand into open habitats.^[7] This swallow usually nests in the area it bred the year before; only about 14% of females and 4% of males disperse to breed at a new site per year. Most do not go far, usually breeding at sites less than 10 kilometres (6.2 mi) away from their original grounds. Dispersal is influenced by breeding success; of the adult females that fail to fledge a chick, about 28% disperse, compared to 5% of successful breeders.^[25] Natal dispersal (when a bird does not return to the site it was born at to breed) is common in the tree swallow and occurs more frequently than breeding dispersal.^[28] It nests both in loose groups and isolated pairs. When nesting in loose groups, nests are usually spaced at least 10 to 15 metres (33 to 49 ft) apart,^[14] and those that are closer in distance are usually further apart in terms of laying date.^[29] In natural cavities, the tree swallow nests about 27 metres (89 ft) apart from its neighbor. The nest hole in these situations is, on average, 3.4 metres (11 ft) above ground level, although about 45% of them are less than 2 metres (6.6 ft) above the ground. Higher cavities are likely favoured because they reduce predation, while lower nest holes may be chosen to avoid competition. Entrance widths are often between 4 and 5 centimetres (1.6 and 2.0 in), whereas entrance heights are more variable: a 1989 study found openings ranging from 3.5 to 26 centimetres (1.4 to 10.2 in). Cavity volume is generally below 1,000 cm³ (61 cu in).^[30] After finding a suitable place to nest, the male perches near it and calls frequently. A lack of sites can cause fights between birds, sometimes resulting in deaths. This swallow usually defends an area around the nest with a radius of about 4.6 metres (15 ft),^[7] as well as extra nests inside of that territory,^[14] by blocking the entrance to the nest and chasing intruders.^[7] The nest cup itself is made from grass, moss, pine needles, and aquatic plants collected mostly by the female,^[14] and is lined with feathers gathered primarily by the male in fights.^[31] The feathers may function to insulate the nest, decreasing incubation time^[32] and likely preventing hypothermia in chicks. In addition to faster growth for chicks,^[31] eggs cool slower in nests with feathers than those without.^[33] However, a study published in 2018 did not find a significant correlation between the number of feathers in nests that were artificially warmed versus those that were not. Additionally, it found that nests in St. Denis, Saskatchewan used significantly less feathers than those in Annapolis Valley, despite the former being further north. However, temperatures in Nova Scotia (where Annapolis Valley is) are generally lower than those in Saskatchewan, possibly explaining the unexpected result.^[34]

A pair mating

During courtship, a male tree swallow attacks an unknown female. This can be stimulated through wing-fluttering flight by the female, which may be an invitation to court. The male may then take a vertical posture, with a raised and slightly spread tail and wings flicked and slightly drooped. This prompts the female to try to land on the male's back, but he flies to prevent this; this is repeated. After courting the female, the male flies to his chosen nest site, which the female inspects. During copulation, the male hovers over the female, and then mounts her, giving ticking calls. He then makes cloacal contact with the female while holding her neck feathers in his bill and standing on her slightly outstretched wings. Copulation occurs multiple times.^[7]

Eggs are laid from early May to mid-June (although this is happening earlier due to climate change^[35]) and chicks fledge between mid-June and July.^[14] Latitude is positively correlated with laying date,^[14] while female age and wing length (longer wings allow more efficient foraging^[36]) are negatively correlated.^[37] The tree swallow is likely an income breeder, as it breeds based on food abundance and temperatures during the laying season.^[36] This species is generally socially monogamous, but up to 8% of breeding males are polygynous.^[14] Polygyny is influenced by territory: males having territories with nest boxes at least 5 metres (16 ft) apart are more likely to be polygynous.^[38] It is suggested that this polygyny depends on the conditions during the laying season: better conditions, such as an abundance of food, allow females in polygyny who do not receive help foraging to lay more eggs.^[39]

The inside of a tree swallow nest

The tree swallow has high rates of extra-pair paternity, 38% to 69% of nestlings being a product of extra-pair paternity, and 50% to 87% of broods containing at least one nestling that was the result of an extra-pair copulation.^[14] One factor that might contribute to this is that females have control over copulation, making paternity guards ineffective.^[40] This may be mitigated by more frequent copulations just before egg laying, according to a 2009 study which found that within-pair copulation attempts peaked three to one days before the first egg was laid and that more successful attempts during this period increased the share of within-pair young males had. This latter finding contradicts those of a 1993 and a 1994 study.^[41] Extra-pair paternity does not change the level of parental care the male contributes in the tree swallow.^[42] A significant number of extra-pair fathers may be floaters (those present at breeding grounds that presumably do not breed). A 2001 study found that out of 35 extra-pair nestlings, 25 were sired by local residents, three by residents of nearby sites, and seven by male floaters. In the tree swallow, floating thus helps males in good condition produce more chicks, while allowing males in bad condition to be successful by investing in parental care.^[43] There is also a significant population of female floaters; a 1985 study estimated that around 23% to 27% of females were floaters, of which about 47% to 79% were subadults.^[44]

Why females engage in extra-pair copulation and how they choose extra-pair mates is controversial. One theory, called the genetic compatibility hypothesis, states that increased offspring fitness results from increased heterozygosity, and thus that female tree swallows would prefer to mate with males that are less genetically similar to them. Females may also choose sperm after copulation to ensure a compatible mate. In support of this theory, a 2007 study found that extra-pair offspring were more heterozygous than within-pair offspring.^[45] However, a 2005 paper discovered a slight negative correlation between a pair's genetic similarity and the proportion of extra-pair young in their nest.^[46] The good genes theory says that females choose extra-pair males based on the quality of their genes. This would explain why some tree swallows do not have any extra-pair young, whereas others do.^[40] However, most studies have not found phenotypic differences between extra-pair and within-pair males (although a 2007 study did find that older males with brighter plumage were more likely to mate outside of the pair bond).^[47] Additionally, according to a 2017 thesis, extra-pair offspring are no more likely to join their natal population than within-pair offspring. Another theory suggests that extra-pair paternity is context dependent, with extra-pair young outperforming within-pair young in certain situations, and underperforming in other environments. A 2017 dissertation, for example, found that extra-pair young were larger, heavier, and longer-winged than within-pair young when both were exposed to predator mounts, while within-pair young were heavier than extra-pair young when they were shown non-predator mounts. This thesis also found that within-pair young outperformed extra-pair young in terms of life-time fitness when they were raised in less-variable environments, suggesting that extra-pair offspring have less developmental plasticity than within-pair offspring.^[48] A 2018 study weakly supported this context dependent hypothesis, finding that extra-pair offspring were more likely to fledge than within-pair offspring in experimentally enlarged broods; however, neither telomere length (a correlate of survival and reproductive success) nor size 12 days after hatching were significantly different among these young, and no significant differences between the two types were found in non-enlarged broods.^[49]

Studies attempting to prove the adaptability of extra-pair paternity for females have been criticized for the lack of positive effect that increased offspring fitness would have when compared with the potential cost of decreased fitness for the female,^[50] such as increased predation from searching for mates.^[51] Thus, theories based on the non-adaptivity of extra-pair paternity for females have been postulated. These theories are based on genetic constraint, where an allele resulting in a maladaptive behaviour is maintained because it also contributes to a beneficial phenotype. The theory of intersexual antagonistic pleiotropy says that strong selection for extra-pair paternity in males (as seen in this bird^[50]) overrides the weak selection against extra-pair paternity in females. The hypothesis of intrasexual antagonistic pleiotropy, meanwhile, argues that extra-pair paternity is present because the genes regulating it have pleiotropic effects on aspects of female fitness,^[52] like within-pair copulation rate.^[50]

A tree swallow egg

The tree swallow lays a clutch of two to eight, although usually four to seven,^[14] pure white, and translucent at laying, eggs that measure about 19 by 14 mm (0.75 by 0.55 in).^[53] These eggs are incubated by the female,^[14] usually after the second-to-last egg is laid,^[54] for 11 to 20 days,^[53] although most hatch after 14 to 15 days. About 88% of nests produce at least one nestling, but this can be lowered by poor weather and a younger breeding female.^[14] The eggs generally hatch in the order they were laid. They also hatch slightly asynchronously, with an average of 28 hours between when the first and final nestling emerges. This can result in a weight hierarchy where earlier-hatched chicks weigh more (especially early in the nestling period) than those hatched later, allowing the female to prioritize which chick to give food to during food shortages. This likely has its greatest effect early in the nestling period, as by 12 days after hatching, there are generally no significant weight differences.^[54] Infanticide of the chicks and eggs sometimes occurs when a male is replaced by another male. Infanticide usually does not occur when the clutch is not complete, as replacement males then have a chance to fertilize at least one egg. When the male arrives during incubation, it sometimes commits infanticide, but other times adopts the eggs, as there is a chance that some eggs were sired from the replacement male. If the replacement male arrives after the chicks hatch, infanticide is usually committed, though the female will sometimes prevent this.^[55]

Nests produced by females of better condition often have sex ratios skewed towards high quality males. A 2000 study hypothesized this to be because males have more variable reproductive success, and therefore that a high quality male produces more offspring than a female of similar quality.^[56]

The growth and survival of nestling tree swallows is influenced by their environment. In both younger and older nestlings (those between two and four days old and between nine and eleven days, respectively) growth is positively influenced by a higher maximum temperature, particularly in the former. A later hatching date negatively impacts growth, especially for younger nestlings. Older chicks grow somewhat faster when insects are abundant. Growth in younger nestlings increases with age, while in old nestlings, it decreases as they get older.^[57] Young tree swallows are able to thermoregulate at least 75% as effectively as the adult at an average age of 9.5 days when out of the nest, and from four to eight days old when in the nest (depending on the size of the brood).^[58] The nestlings fledge after about 18 to 22 days, with about 80% fledging success. Like hatching success, this is negatively affected by unfavourable weather and a younger female.^[14] Chicks may be preyed on by snakes^[59] and raccoons.^[60] This predation can be exacerbated by begging calls.^[61]

Feeding

Flying in Central New York, US

The tree swallow forages up to 50 metres (160 ft) above the ground singly or in groups. Its flight is a mix of flapping and gliding. During the breeding season, this is mostly within 4 kilometres (2.5 mi) of the nest site. When it is foraging for nestlings, though, it usually goes up to 200 metres (660 ft) from the nest,^[14] mostly staying in sight of it, and forages at a height up to 12 metres (39 ft).^[62] As well as being caught in flight,^[7] insects are sometimes taken from the ground, water, vegetation, and vertical surfaces.^[14]

The tree swallow eats mostly insects, with some molluscs, spiders, and fruit. In North America, flies make up about 40% of the diet, supplemented with beetles and ants. Otherwise, the diet is about 90% flies.^[14] The insects taken are a mix of aquatic and terrestrial organisms; the former are an important source of omega-3 highly unsaturated fatty acids. This is because, although the tree swallow can convert the precursor α-Linolenic acid into highly unsaturated fatty acids like docosahexaenoic acid, it cannot do so in the quantities needed.^[63] The seed and berry food is mainly from the genus Myrica, which is mainly taken in all four of the Northern Hemisphere seasons except summer. Crustaceans were also found to be important in the wintering diet in a study on Long Island, New York.^[14]

A chick being fed

Both sexes feed the nestlings (although the male feeds the chicks less than the females) resulting in about 10 to 20 feedings per hour.^[14] The parents often use the chirp call to stimulate nestlings to beg. This is used more frequently with younger chicks, as they beg less than older chicks when the parent arrives with food but does not call.^[19] The likelihood of begging in the absence of parents also increases with age.^[64] The hatching order affects how much a chick is fed; last-hatched nestlings (in cases where hatching is asynchronous) are likely fed less than those hatched earlier.^[65] Nestlings closer to the entrance of the nest are also more likely to be fed, as are those who beg first^[66] and more frequently. The overall rate at which a brood is fed also increases with more begging.^[67] The diet itself is composed mostly of insects, those in the orders Diptera, Hemiptera, and Odonata making up most of the diet.^[14] These insects are mostly up to 10 mm (0.39 in) in size, but sometimes are up to 60 mm (2.4 in) in length.^[62] In nests near lakes acidified by humans, calcium supplements, primarily fish bones, crayfish exoskeletons, clam shells, and the shells of bird eggs, are harder to find. This forces the adult tree swallow to travel further than usual—sometimes up to 650 m (2,130 ft) away from the nest—to get these calcium supplements.^[68]

Survival

The tree swallow has an average lifespan of 2.7 years^[69] and a maximum of 12 years. About 79% of individuals do not survive their first year, and those that do face an annual mortality rate of 40% to 60%.^[14] Most deaths are likely the result of cold weather, which reduces insect availability, leading to starvation.^[7] Lifespan is associated with telomere length: a 2005 study that used return rates (to the breeding site of the previous year) as a proxy for survival found that those with the longest telomeres at one year of age had a predicted lifespan of 3.5 years, compared to the 1.2 years for those with the shortest telomeres.^[70] Whether short telomeres cause a reduction in fitness or are simply an indicator of it is unknown. Regardless, a 2016 thesis found that measures of condition were positively correlated with telomere length. Males also generally had longer telomeres than females, as did smaller-winged birds. Individuals with shorter telomeres may compensate for potential losses in fitness by increasing reproductive effort, whereas those with longer telomeres may decrease their investment, as evidenced by the smaller proportion of chicks females with longer telomeres fledged.^[71] Telomere length is highly heritable, and is especially dependent on that of the mother.^[72]

Predation

The tree swallow is susceptible to a wide range of predators. Eggs, nestlings, and adults in the nest fall victim to black rat snakes, American crows, American kestrels, common grackles, northern flickers, chipmunks, deermice, domestic cats, weasels,^[73] American black bears,^[74] and raccoons.^[75] While flying or perched, predators to the tree swallow include American kestrels, black-billed magpies,^[73] barred owls,^[76] great horned owls, merlins, peregrine falcons, and sharp-shinned hawks. Whilst evasive flight is the usual response to predators in free-flying swallows, mobbing behavior is common around the nest,^[73] and is directed not just towards predators, but also towards nest site competitors, who might be scared off by it.^[20] This behaviour involves the swallow swarming and diving towards (but not actually striking) the intruder^[73] from around 5 to 20 m (16 to 66 ft) above the ground, usually giving soft ticking calls near the end and coming within about 0.5 to 2 m (1.6 to 6.6 ft) of the predator.^[20] It seems to alter the intensity of its attacks based on which predator approaches;^[73] a 1992 study found that ferrets elicited a more vigorous defence than black rat snakes,^[20] and a 2019 thesis similarly discovered that black rat snake models were dived at the least and eastern chipmunk models the most.^[77] It is suggested that the snake prompted a weaker response because defence behaviours may be less effective^[20] and more dangerous to perform against it.^[77]

Parasites

Blow-fly in the genus Protocalliphora

The tree swallow is vulnerable to various parasites, such as the blood parasite Trypanosoma. It is also susceptible to the flea Ceratophyllus idius and the feather mites Pteronyssoides tyrrelli, Trouessartia, and (likely) Hemialges. It is also probably afflicted by lice of the genera Brueelia and Myrsidea. There is a correlation between the number of fleas on a bird and the number of young it is caring for. This relationship is speculated to arise from an improved microclimate for fleas due to a larger clutch.^[78] Nestlings also suffer from parasites, like blow-flies of the genus Protocalliphora,^[79] which results in a loss of blood by nestlings.^[80] These parasites, though, are found in a majority of nests and do not seem to have a large effect on nestlings. A study published in 1992 found that the effects of blow-fly parasitism explained only about 5.5% of the variation in nestling mass.^[79]

Immunology

In the breeding female tree swallow, humoral immunocompetence (HIC) is inversely correlated with laying date. This means that, on average, a bird that lays its eggs earlier has a stronger antibiotic response to an antigen than a bird that lays later. A tree swallow that is handicapped by wing-clipping generally has a lower HIC. These relationships could be interpreted as supporting the conclusion that a female that lays earlier acquires a higher HIC, but the authors of the study that found the correlations believed this unlikely, due to the colder temperatures near the start of the breeding season. Instead, they thought that HIC could be a measure of quality, and that a higher quality female is able to lay earlier. The authors also postulated that it is an indicator of workload, as shown by the lower HIC of handicapped birds.^[81]

Higher quality female tree swallows (as measured by laying date) are able to maintain their reproductive effort while diverting resources to fight an immune challenge. Lower quality swallows are less able to do so; a 2005 study in Ithaca, New York, found that late-laying females with an artificially enlarged brood, although able to maintain offspring quality, had lower responses to an immune challenge than those that were of higher quality or did not have an enlarged brood.^[82] Whether a female chooses to prioritize offspring quality or immunocompetence is likely related to survival probabilities; a 2005 study discovered that females with an enlarged brood in Alaska, where survival rates are lower, had weaker immune responses, but kept reproductive effort steady, whereas those in Tennessee, with higher survival rates, had a stronger response but lower quality offspring.^[83]

In the tree swallow, some components of the immune system deteriorate with age. Acquired T cell-mediated immunity, for example, declines with age in the female tree swallow. But, the age of a female does not affect both the acquired and innate humoral immunity; the lack of deterioration in the former contrasts with studies on barn swallows and female collared flycatchers.^[84] Because of this immunosenescence (a decrease in immune function with age), older females infected with a disease generally visit their nest less, resulting in their nestlings growing slower. They are also likely to lose weight because of an infection.^[85]

Status

The tree swallow is considered to be least concern by the International Union for Conservation of Nature. This is due to the bird's large range of about 834,000 km² (322,000 sq mi),^[1] and its stable population, estimated to be about 20,000,000 individuals.^[14] It is protected in the US by the Migratory Bird Treaty Act of 1918,^[86] and in Canada by the Migratory Birds Convention Act.^[87] In some parts of the US, the range of this swallow has extended south, likely due to changes in land use, the reintroduction of beavers, and nest boxes installed for bluebirds. The tree swallow is negatively impacted by the clearing of forests and the reduction of marshes, the latter reducing the habitat available for wintering. This swallow has to compete for nest sites with the common starling, house sparrow (both introduced to North America),^[14] bluebirds,^[88] and the house wren (which also destroys nests without occupying them).^[89] Acidification of lakes can force this swallow to go relatively long distances to find calcium-rich items, and can result in chicks eating plastic.^[68] Other chemicals, like pesticides and other pollutants, can become highly concentrated in eggs, and PCBs are associated with the abandonment of a pair's clutch.^[14] Contamination from oil sands mine sites can negatively affect tree swallows by increasing the presence of toxins, as measured by the activity of ethoxyresorufin-o-deethylase (a detoxification enzyme) in nestlings. This normally has little influence on nestling and fledging,^[90] though extreme weather can reveal the effects: a 2006 study found that nestlings from wetlands most polluted by oil sands processing material were more than 10 times more likely to die than those from a control site during periods of synchronized cold temperatures and heavy rainfall, compared to the lack of difference in mortality between the groups when the weather was less extreme.^[91] A 2019 paper, however, found that increased precipitation caused a similar decline in hatching and nestling success for nestlings both near and far from oil sands sites.^[92] In another study, birds exposed to mercury fledged, on average, one less chick than those not, an effect amplified by warm weather.^[93] In addition, cold weather events can rapidly reduce the availability of aerial insect prey,^[94] and in some populations with advancing reproduction may result in reduced offspring survival.^[95]

References

Notes

Citations

La Dukolora hirundo, Tachycineta bicolor, estas migranta paserina birdo el la familio de hirundedoj (Hirundinidae). En la angla ĝi nomiĝas Tree Swallow (Arbohirundo), ĉar ĝi nestumas foje ene de arbotruoj.

Disvastiĝo

Tutmonda distribuado

Ĝi reproduktiĝas en Nordameriko kaj vintrumas en Meksiko, Centrameriko kaj Karibio. Ĝi estas tre rara varanto al okcidenta Eŭropo.

Aspekto

Tiu hirundo mezaveraĝe estas 13.5 cm longa kaj peza ĉirkaŭ 20 g. La beko estas eta. La plenkreskulo de Dukolora hirundo havas brilajn bluverdnigrecajn suprajn partojn, tre blankajn subajn partojn (el la beko suben), kaj iom forkoforman voston. La kontrasto inter ambaŭ partoj estas tre rimarkinda pro la pura blanko de la subaj partoj kaj la malhelo de la supraj; de tie devenas la esperanta kaj la scienca latina nomoj. Fakte la distribuo de la bluo kaj nigro ne estas homogena, sed laŭ la partoj: tiele la frunto, krono kaj sub kaj malantaŭ la okulo estas pli bluaj, dum la nuko kaj flugilplumoj estas pli nigraj kaj masko komponita de beko, alokula strio kaj okulo estas tute nigra kiel dividilo inter la bluaj supraj partoj kaj la blankega gorĝo kaj la aliaj subaj partoj. La kruroj estas rozkoloraj kaj la ungoj nigrecaj. La ino kutime havas pli senkolorajn kolorojn ol la masklo, ofte pli verdeca ol la pli blua masklo. La plumaro de junuloj estas pli simple grizbruna supre kaj povas havi nuancojn de griza brustozono.

Reproduktado

La Dukolora hirundo nestumas en naturaj aŭ artefaritaj kavaĵoj ĉe akvo kaj ofte troviĝas en grandaj aroj. Ili facile akceptas uzi nestoskatolojn, inklude tiujn konstruitajn por blubirdoj.

Seksumantaj Dukoloraj hirundoj.

La nesto de Dukolora hirundo konsistas el nombraj tavoloj de herberoj kaj fajnegajn bastonetojn kaj ĝi estas kovrita de grandaj plumoj de aliaj specioj. La ino demetas 4 al 7 blankajn ovojn kaj kovas ilin nur ŝi. Eloviĝo okazas post ĉirkaŭ 14 tagoj kaj elnestiĝo post pliaj 16-24 tagoj. Dum kovado kak idozorgado plenkreskuloj ofte atakas entrudulojn (inklude scivolemajn homojn) por sekurigi la nestareon. Oni scias ke la Dukolora hirundo luktokaptas plumojn dumfluge, eble por pariĝada ceremonio aŭ simple kiel ludo.

Ĉe Dukolora hirundo kutime okazas nur unika ovodemetado, sed ili povas klopodi duan se la unua malsukcesas frue en la sezono. Oni scias pri kazoj de du sinsekvaj sukcesaj ovodemetadoj en unu sezono.

Ili manĝas ĉefe insektojn, foje suplementitaj de eta kvanto de frukto. Ili estas elstaraj flugantoj kaj elsaltas el ripozejo kaj akrobate kaptas insektojn en siaj bekoj dumfluge.

Masklo de Dukolora hirundo.

Referencoj

• BirdLife International (2004). Tachycineta bicolor. Internacia Ruĝa Listo de Endanĝeritaj Specioj, eldono de 2006. IUCN 2006. Elŝutita 12a Majo 2006. Malplej zorgiga

Ekŝteraj ligoj

Apareamiento.

La golondrina bicolor (Tachycineta bicolor) es una especie de ave paseriforme migratoria de la familia Hirundinidae que se reproduce en América del Norte y pasa los inviernos en México, América Central y el Caribe. Raramente aparece en Europa occidental.

Esta golondrina tiene un tamaño promedio de 13,5 cm (5 pulgadas) de largo y pesa unos 20 g. El pico es muy pequeño. La golondrina bicolor adulta tiene partes superiores de color verde iridiscentes, vientre blanco y una cola muy ligeramente bífida. La hembra generalmente tiene colores más opacos que el macho, más verde mientras que el macho es más azulado. El plumaje juvenil es gris marrón en la parte superior y puede tener una banda de pecho de color gris.

Altamente social fuera de la estación de cría, las golondrinas bicolor pueden formar bandadas de varios miles de aves cerca de los sitios de reproducción.^[1]​ Los grupos cerca de Vacherie, Luisiana, se estimó que tenían más de 1 millón de aves durante diciembre de 2009.^[2]​

Reproducción

Las golondrinas bicolor anidan en cavidades natural o artificiales cerca de agua y se encuentran a menudo en grandes bandadas. Ellas utilizan fácilmente cajas como nidos, incluyendo las construidas para azulejos. Disminuciones en las poblaciones de constructores de cavidades resultando en menos sitios de anidación naturales para golondrinas bicolor, aunque la población de permanece estable.

El nido de la glondrina bicolor consiste en múltiples capas de hierbas y ramas delgadas y está llena de grandes plumas de otras especies. La hembra pone de 4 a 7 huevos blancos e incuba ella misma. Los huevos eclosionan en unos 14 días y las crías son altriciales. Las crías vuelan normalmente en 16 a 24 días. Mientras que hay jóvenes o huevos en el nido, los adultos con frecuencia atacan intrusos (incluidos a los humanos curiosos) e intentan echarlos de la zona. Las golondrinas bicolor suelen "pelear" por plumas en el aire por razones que están todavía bajo investigación. Hay algunas especulaciones de que esto es una forma de juego.

Las golondrinas bicolor hacen normalmente un solo nido, aunque puede intentar un segundo nido si la primera falla temprano en la temporada. Hay registros de padres criando dos crías exitosamente en una temporada.

Subsisten principalmente con una dieta de insectos, a veces complementado con pequeñas cantidades de frutas. Son excelentes voladores y atrapan acrobáticamente insectos en el aire.

Referencias

• BirdLife International (2004). «Tachycineta bicolor». Lista Roja de especies amenazadas de la UICN 2006 (en inglés). ISSN 2307-8235. Consultado el 12 de mayo de 2006. Database entry includes justification for why this species is of least concern

Zuhaitz-enara (Tachycineta bicolor) Tachycineta generoko animalia da. Hegaztien barruko Hirundinidae familian sailkatua dago.

Erreferentziak

Kanpo estekak

• World Bird Names

Ikus, gainera

• Tachycineta
• Hirundinidae

Kelopääsky (Tachycineta bicolor) on Pohjois-Amerikassa pesivä pääskyihin kuuluva varpuslintu. Se on pienehkö ja pitkisiipinen pääsky, ja sen vartalon yläpuoli vihertävän sininen ja alapuoli valkoinen. Kelopääskyt ovat sosiaalisia lintuja, ne voivat kerääntyä suuriksi parviksi. Lajin ravinto koostuu pääasiassa hyönteisistä.

Koko ja ulkonäkö

Kelopääsky on kooltaan noin 14 cm. Kelopääsky on pienehkö hyvin pitkäsiipinen pääsky. Selästään, päästään ja siivistään laji on väritykseltään kiiltävän vihertävän sininen. Kurkku, rinta ja vatsa ovat puhtaan valkoiset. Nuoret linnut ovat selästään ja päästään ruskehtavia ja valkoisessa rinnassa on myös harmaata.^[2] Naaraiden höyhenpuku kehittyy hitaammin kuin koiraan.^[3]

Levinneisyys ja elinympäristö

Kelopääsky pesii Pohjois-Amerikan pohjois- ja keskiosissa. Lajin levinneisyyden pohjoisraja noudattaa melko tarkasti puurajaa. Lajin talvehtimisalueet ovat Floridassa sekä Keski-Amerikassa Karibianmeren rannikolla. Lajin elinympäristöä ovat avoimet alueet lähellä vesialueita kuten pellot, suot, niityt, rannat ja majavalampien läheiset alueet.^[2]

Ravinto

Kelopääskyjen ravinto koostuu pääasiassa hyönteisistä, joita laji pyydystää ilmasta avoimien maa-alueiden tai veden päältä. Laji syö erityisesti perhosia, kovakuoriaisia ja muurahaisia, mutta myös heinäsirkkoja, korentoja ja vesiperhosia.^[2] Toisin kuin monet muut pääskyt kelopääskyt voivat elää pitkiäkin aikoja ilman hyönteisravintoa, jolloin ne syövät marjoja, erityisesti myrttien (Myrica) vahapintaisia marjoja.^[3]

Elintavat

Pesimäkauden ulkopuolella kelopääskyt ovat hyvin sosiaalisia lintuja ja voivat kerääntyä hyvin suuriksi jopa satojen tuhansien yksilöiden parviksi yöpymispaikoilleen.^[3] Pesimäkauden aikaan ne ovat kuitenkin hyvin tarkkoja reviireistään ja molemmat vanhemmat puolustavat aluetta, joka ulottuu noin 10–15 metrin säteelle pesäpaikasta.^[2]

Kelopääskyjen pesimäkausi kestää toukokuulta syyskuulle. Pesä sijaitsee yleensä puunkolossa tai pesälaatikossa. Laji voi rakentaa pesän myös rakennuksiin tai siltarumpuihin. Naaras munii kahdesta kahdeksaan valkoista munaa, joita vain se hautoo kahdesta kolmeen viikkoon. Koiras osallistuu poikasten ruokintaan.^[2]

Kelopääskyt muuttavat päiväsaikaan löyhinä parvina ja yöpyvät suurina ryhminä.^[2]

Vain kelopääskykoiras laulaa. Linnut pitävät yhteyttä keskenään kutsuäänillä, joita on lajilla 14 erilaista. Lisäksi linnut käyttävät kehonkieltä esimerkiksi värisyttämällä siipiään tai kyyristymällä. Näillä tavoin lintu voi ilmaista aggressiotaan ja lintu käyttää näitä myös pariutuakseen.^[2]

Lähteet

Tachycineta bicolor

L'Hirondelle bicolore (Tachycineta bicolor) est une espèce de passereaux appartenant à la famille des Hirundinidae.

Description

Cet oiseau mesure environ 13,5 cm et pèse environ 20 g. Il a le dos bleu-vert iridescent, la poitrine blanche et le bec noir.

Un dichromatisme sexuel existe entre les mâles et les femelles. Les femelles sont plus vertes et moins brillantes que les mâles^[1]. La coloration iridescente de l’Hirondelle est formée par la microstructure de la plume. La superposition d’une couche mince et uniforme de granules de mélanine sous une couche de kératine dans les barbules des plumes^[2] amène le phénomène physique appelé «interférence par couches minces». C’est le même phénomène qui crée la coloration observée sur une bulle de savon ou sur de l’huile sur de l’eau.

Les femelles ont une particularité appelée la maturation retardée du plumage^[3]. Les femelles âgées d’un an ont un plumage brun similaire à celui des jeunes de l’année, parfois avec une légère coloration verte. Il est proposé que ce plumage brun diminue les agressions faites par les autres femelles. Cette espèce est une des rares chez qui on observe ce phénomène chez les femelles.

Un mâle (à gauche) et une femelle brune âgée d'un an d'Hirondelle bicolore.

Une hirondelle bicolore dans le Jamaica Bay Wildlife Refuge (en) à New York. Mai 2021.

Par la couleur seulement, il est possible de distinguer les femelles d’un an brunes des autres (femelles de 2 ans et mâles). Lorsqu’on a affaire à un mâle et une femelle tous deux iridescents, on ne doit pas se fier seulement à la couleur, puisque certaines femelles peuvent être aussi bleues et brillantes que certains mâles. Il faut se fier aussi à ces autres critères^[4] :

• Le mâle est plus gros et a souvent les plumes hérissées (particulièrement celles de la couronne) et a souvent la poitrine d’un blanc plus éclatant;
• Le mâle est plus constamment perché sur le nichoir et attaque plus les intrus entrant dans une zone de 15 m du nichoir;
• La femelle iridescente peut avoir une bande de plumes brunes autour du bec.

La mue s’effectue durant l’automne, parfois certaines plumes de la couronne muent durant l’hiver^[1].

Répartition

• zone de nidification
• voie de passage
• aire d'hivernage

L’hirondelle bicolore est un passereau migrateur nichant en Amérique du Nord et hivernant au Mexique, en Amérique centrale et dans les Caraïbes.

Habitat

Cet oiseau préfère les habitats ouverts comme les plans d’eau et les champs agricoles^[1].

Alimentation

Il est insectivore aérien.

Nidification

Il est nicheur cavicole secondaire, c’est-à-dire qu’il niche dans des trous que d’autres oiseaux ont déjà formés dans des arbres morts (exemple : pic, canard) et s’accommode bien de nichoirs artificiels^[1]. L’hirondelle bicolore est la première hirondelle à arriver au Québec^[5]. La raison est qu’elle est la seule à pouvoir s’alimenter d’autre chose que des insectes, comme les baies du myrique beaumier^[1]. Le mâle arrive avant la femelle, et revient souvent au même territoire année après année. La femelle est moins philopatrique^[6]. Ainsi, plus souvent les individus ne forment pas le même couple année après année^[7].

Nid typique de l'Hirondelle bicolore. Ici, une femelle de plus d'un an incube ses œufs.

Comme l’hirondelle est un nicheur cavicole secondaire, les sites de nidification sont plutôt rares, ainsi elle a un comportement agressif envers les autres individus lors de la nidification (les mâles comme les femelles)^[1]. Une fois le couple formé, la femelle entreprend la construction du nid seule (avec des herbes séchées en grande partie), et le mâle peut ajouter la touche finale par des plumes de d’autres espèces qu’il va chercher aux alentours, par exemple des plumes de goéland et de dindon. Les mâles semblent jouer entre eux avec les plumes en vol^[1]. Lorsqu’on laisse tomber une plume près d’un mâle, il tend à aller la chercher en vol.

La femelle pond entre 4 et 6, rarement 7, œufs blancs. Elle pond ses œufs le matin, à raison de 1 par jour. La fertilisation se fait par le mâle du couple, mais aussi avec d’autres mâles des environs. La femelle a été observée s’éloigner jusqu’à 10 km de son nichoir durant sa période fertile^[8], ainsi les reproductions hors couple peuvent se faire relativement loin. La femelle semble contrôler les reproductions hors couple, puisqu’elle a été vue les solliciter mais aussi exprimer un refus de copulation (en soulevant la queue) sans agression de la part du mâle^[9].

Oisillon probablement âgé d'environ 20 jours prêt à s'envoler.

Les oisillons sont nidicoles, donc naissent sans plumes et très petits, après environ 14-15 jours d’incubation. Ils prennent environ 16-22 jours gagner une vingtaine de grammes et s’envoler^[1]. Le mâle et la femelle se partagent la tâche des soins aux oisillons (apport d’insectes et retrait des fientes hors du nid). Le mâle effectue des soins même si tous les oisillons ne sont parfois pas les siens. En moyenne, 50 % des jeunes de la nichée sont les siens, et 85 % des nichées contiennent au moins 1 oisillon hors couple^[10]. Il s’agit donc d’une des espèces avec le plus grand taux de reproductions hors couple observé chez les oiseaux^[11].

Des études ont été faites sur la sélection sexuelle de la coloration chez les mâles. Les mâles plus brillants ont plus de jeunes hors couple, c’est-à-dire des jeunes produits dans d’autres nids que le sien^[12]. Les femelles plus vertes et moins brillantes ont un meilleur succès reproducteur^[13].

Longévité

Cet oiseau vit en moyenne 2,7 ans mais certains individus atteignent 8 ans^[14].

Population et conservation

Cet oiseau fait partie du groupe des oiseaux des prairies, le groupe d’oiseaux ayant subi le plus fort déclin en Amérique du Nord depuis 1970. L’hirondelle bicolore subit au Québec un déclin de 4 % par année depuis 1970^[15].

Notes et références

La rondine arboricola bicolore (Tachycineta bicolor (Vieillot, 1808)) è un uccello della famiglia Hirundinidae.^[1]

Note

De boomzwaluw ook wel Amerikaanse boomzwaluw (Tachycineta bicolor) is een zangvogel in de familie van de zwaluwen.

Kenmerken

Deze boomzwaluw wordt gemiddeld 13,5 cm lang en heeft een gewicht van rond de 20 gram. De bek is klein. De volwassen boomzwaluw heeft glanzende blauw-groene bovendelen, een witte buik en een licht gevorkte staart. Het vrouwtje heeft in het algemeen doffere kleuren dan het mannetje en is vaak groener dan het mannetje, welke juist vaak blauwer is. Het verenkleed van de kuikens heeft een doffe grijs-bruine kleur aan de bovenkant en kan een grijze borstband hebben.

Leefwijze

Buiten het broedseizoen is de boomzwaluw een zeer sociale soort en vormt dan soms ook zwermen van enkele duizenden vogels. Zwermen bij Vacherie (Louisiana) werden geschat op ruim 1 miljoen vogels in december 2009. De boomzwaluw voedt zich met name met insecten, soms aangevuld met kleine hoeveelheden fruit. Hij is een uitstekende vlieger en is in staat vanaf de stok op te stijgen en in de lucht insecten te vangen.

Voortplanting

Parende boomzaluwen.

Een boomzwaluw in vlucht in New York.

Boomzwaluwen nestelen in natuurlijke en kunstmatige holtes bij het water en kunnen vaak worden gevonden in grote zwermen. Ze maken gretig gebruik van nestkasten, waaronder die gebouwd voor Sialia. Een daling van het aantal holtebouwende populaties resulteert in minder natuurlijke broedplaatsen voor boomzaluwen, hoewel de zwaluwbevolking gezond en stabiel blijft.

Het nest bestaat uit verschillende lagen gras en takjes en is bekleed met grote veren van andere soorten. Het vrouwtje legt 4 tot 7 witte eieren en broedt ze zelf uit. De eieren komen na ongeveer 14 dagen uit. De jongen zijn nestblijvers en vliegen na 16 tot 24 dagen uit. Als er jongen of eieren in het nest zijn maken de volwassenen regelmatig duikvluchten richting indringers (inclusief nieuwsgierige mensen) om ze van het gebied te verdrijven. Boomzaluwen staan er bekend om dat ze in de lucht om veren "vechten". De reden hiervoor is nog onbekend, maar er is enige speculatie dat het om een vorm van spelen zou gaan.

Boomzwaluwen maken over het algemeen één nest per seizoen, hoewel ze soms een tweede nest proberen als de eerste vroeg in het seizoen faalt. Er zijn verslagen van ouders die twee succesvolle broedsels in één seizoen opvoedden.

Verspreiding en leefgebied

In Australië komt een ander soort zwaluw voor die ook boomzwaluw wordt genoemd, de Australische boomzwaluw (Petrochelidon nigricans). De Amerikaanse boomzwaluw is een trekvogel die broedt in Noord-Amerika en overwintert in Mexico, Midden-Amerika en de Caraïben. In zeldzame gevallen zwerven vogels van deze soort naar West-Europa.

• Dit artikel of een eerdere versie ervan is (gedeeltelijk) vertaald vanaf de Engelstalige Wikipedia, die onder de licentie Creative Commons Naamsvermelding/Gelijk delen valt. Zie de bewerkingsgeschiedenis aldaar.
  

Nadobniczka drzewna (Tachycineta bicolor) – gatunek ptaka z rodziny jaskółkowatych (Hirundinidae). Jedyny gatunek wśród północnoamerykańskich ptaków śpiewających, u którego samica gnieździ się w szacie młodocianej.

Wygląd

Długość ciała 12-15 cm. Samiec - wierzch ciała metalicznie niebieskozielony, od spodu biały. Samica - 1 rok jest brązowa, z niewielką ilością metalicznego nalotu na wierzchu, od spodu biała. W drugim roku ilość nalotu zaczyna się zwiększać.

Zasięg, środowisko

Żeruje i gniazduje w pobliżu wód, od północnej granicy lasu po środkową część Ameryki Północnej. Zimuje w południowej części tego kontynentu.

Przypisy

Bibliografia

1. Andrew Gosler: Atlas Ptaków Świata. MULTICO Oficyna Wydawnicza, 2000. ISBN 83-7073-059-0.

A andorinha-das-árvores^[2](Tachycineta bicolor) é uma espécie de pássaro da família Hirundinidae. Encontra-se em estado pouco preocupante, de acordo com a UICN.^[1]

Referências

Trädsvala^[2] (Tachycineta bicolor) är en nordamerikansk fågel i familjen svalor inom ordningen tättingar.^[3]

Utseende och levnadssätt

Trädsvalan är en medelstor (12-14 centimeter)^[4] relativt bredvingad svala med grunt kluven stjärt. Den är alltid vit under och mörk ovan: adult hane metalliskt blågrön, honan med brunare inslag. Vingpennor är svarta, likaså en mask över ögat. Ungfågeln är genomgående brun ovan och ljus under, ibland med ett svagt bröstband.

Trädsvalan är en social fågel som efter häckning och vintertid samlas i stora flockar med flera hundra tusen individer. Jämfört med andra amerikanska svalarter glider den mer i flykten.

Häckning

Trädsvalan påträffas i öppen terräng med fält eller våtmarker, oftast nära vatten. Ursprungligen häckar den i trädhålor, därav namnet, men även gärna i av människan konstruerade svalholkar. Honan lägger en till två kullar med fyra till sju ägg. Även under häckning är fågeln social

Föda

Trädsvalan livnär sig främst av insekter som den fångar i luften, oftast inte mer än 40 meter över marken. När födotillgången är dålig kan den dock även äta växtföda. Under häckningstid intar den också kalciumrika fiskben, kräftdjursskal, äggskal och musselskal.^[5]

Utbredning

Fågeln häckar i stora delar av norra Nordamerika, från Alaska till södra USA. Den flyttar så långt söderut som till norra Sydamerika,^[3] men övervintrar längre norrut än alla andra amerikanska svalarter.^[5] Trädsvalan är en mycket sällsynt gäst i Europa, med två fynd från Storbritannien 1990 och 2002 samt ett från Island 2012.^[6]

Status

Trädsvalan är en vanlig fågel och IUCN kategoriserar arten som livskraftig.^[1] Studier visar dock att den minskat med 49% mellan 1966 och 2014, framför allt i västra och östra delen av utbredningsområdet.^[7] En orskak tros vara minskad tillgång på trädhål för häckning. Värdspopulationen uppskattas till 17 miljoner par.^[8]

Bildgalleri

Noter

1. ^ [a b] Birdlife International 2012 Tachycineta bicolor Från: IUCN 2015. IUCN Red List of Threatened Species. Version 2015.4 www.iucnredlist.org. Läst 2016-02-01.
2. ^ Sveriges ornitologiska förening (2017) Officiella listan över svenska namn på världens fågelarter, läst 2017-08-14
3. ^ [a b] Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood (2015) The eBird/Clements checklist of birds of the world: Version 2015 http://www.birds.cornell.edu/clementschecklist/download, läst 2016-02-11
4. ^ Turner, A. (2017). Tree Swallow (Tachycineta bicolor). I: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (red.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (hämtad från https://www.hbw.com/node/57700 30 december 2017).
5. ^ [a b] Tree Swallow Faktablad om trädsvala på allaboutbird.org
6. ^ Tarsiger.com Fynd av trädsvala i Västpalearktis
7. ^ Sauer, J.R., J.E. Hines, J.E. Fallon, K.L. Pardieck, D.J. Ziolkowski Jr., and W.A. Link. 2011. The North American Breeding Bird Survey, Results and Analysis 1966–2010.
8. ^ Partners in Flight. 2012.

Externa länkar

• Wikimedia Commons har media som rör trädsvala.
  Bilder & media
• Wikispecies har information om Tachycineta bicolor.
  Artförteckning
• Bilder och filmer på Internet Bird Collection
• Läten på xeno-canto.org

Tachycineta bicolor là một loài chim trong họ Hirundinidae.^[1] Được tìm thấy ở châu Mỹ, loài chim này được mô tả lần đầu tiên vào năm 1807 bởi nhà nghiên cứu chim Louis Vieillot của Pháp với danh pháp là Hirundo bicolor. Loài này đã được chuyển đến chi hiện tại của nó, Tachycineta, nơi mà vị trí phát sinh loài của loài này đang tranh cãi. Loài chim này có phần trên màu xanh lam-xanh lục óng ánh, ngoại trừ cánh và đuôi đen, và phần dưới màu trắng. Mỏ có màu đen, mắt có màu nâu đậm, chân và bàn chân có màu nâu nhạt. Chim mái thường nhạt màu hơn chim trống, và con cái năm nhất có phần lớn màu nâu, với một số lông màu xanh. Vị thành niên có phần trên màu nâu, và một bộ ngực màu nâu xám. Các giống cây nuốt ở Mỹ và Canada. Loài này trú đông dọc theo bờ biển phía nam Hoa Kỳ, dọc theo Bờ Vịnh, đến Panama và bờ biển phía tây bắc của Nam Mỹ, và ở Tây Ấn

Chú thích

Tham khảo

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Tachycineta bicolor (Vieillot, 1808)

Вызывающие наименьшие опасения
IUCN 3.1 Least Concern: 22712057

Древесная американская ласточка^[1], или речная ласточка^[1] (лат. Tachycineta bicolor) — американский вид певчих птиц семейства ласточковые.

Описание

Длина тела составляет от 14 до 15 см, а вес — от 18 до 22 г^[2]. Половой диморфизм не выражен. Голова, оперение спины, а также крылья имеют преимущественно окраску от тёмно-синего до сине-чёрного цвета. Горло, грудь и брюхо белёсые. Синеватое оперение при падении света имеет металлический отлив. Нижняя сторона крыльев имеет светло-коричневую окраску. Внешние перья крыльев чаще окрашены в чёрный цвет. В области глаз имеется чёрная полоса. Длинные крылья выходят за рамки хвоста. Ноги очень короткие, также как и пальцы ног. Это является серьёзным препятствием для передвижения по земле. Окраска ног коричневатого цвета. Клюв имеет чёрную окраску. Молодые птицы похожи в окраске оперения на взрослых птиц. Только синеватое оперение имеет частично коричневатую окраску.

Распространение

Древесная американская ласточка — это неарктический вид. Она гнездится на Аляске, на территории центрального Юкона и в Северо-Западных территориях, на южном побережье Гудзонова залива, а также на юге Квебека и на востоке полуострова Лабрадор^[2]. Это перелётная птица, мигрирующая в Центральную Америку на юг Соединённых Штатов, в Мексику и восточное побережье Южной Америки. 9 июня 1939 г. экземпляр был пойман на острове Врангеля^[3].

Питание

Птица, которая часто встречается в больших группах, ловит насекомых в полёте. Наряду с этим она питается ягодами, в том числе плодами лавра, переваривать которые могут лишь немногие виды птиц.

Размножение

Гнездящаяся пара строит в искусственных или естественных пещерах вблизи воды гнездо из растительного материала в форме чаши. Кладку из 4—6 яиц высиживает только самка 15 дней. Через 16—30 дней молодые птицы становятся самостоятельными.

Примечания

ミドリツバメ（学名：Tachycineta bicolor ）は、スズメ目ツバメ科に分類される鳥類の一種。

分布[編集]

アラスカから北アメリカ北部で広く繁殖し、冬期はメキシコ、中央アメリカ、西インド諸島などに渡って越冬する。まれに西ヨーロッパまではぐれてしまうこともある。

日本では、1962年に北海道襟裳岬で灯台に衝突して死亡した個体1羽の採集記録がある迷鳥^{[1] [2]}。

形態[編集]

体長は約13.5cm、体重は約20g。くちばしは小さい。ミドリツバメの成鳥は背面がツヤのある青緑色で腹部は白色である。尾はとても細く分かれている。

生態[編集]

水辺の森に生息し、枯れ木の樹洞等に営巣する。渡りの時期には大きな群れを作り、平地でも普通に観察されるという。鳴き声は「クウィー」「ク、ク、ク」など。

Sibley分類体系上の位置[編集]

脚注[編集]