Corvus frugilegus is classified as a species of least concern on the IUCN's Red List of Threatened Species. Corvus frugilegus is abundant and is able to maintain stable populations in its habitat.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Little is known about predators of rooks. However, they appear to have similar predators to Corvus corax or Corvus brachyrhynchos, both similar and closely related species in the Family Corvidae. Owls, such as Bubo virginianus, hawks, or even intruding species of Corvidae tend to be the primary predators of rooks. Raptorial bird species prey on fledglings from nests more often than attacking adults. Humans may also pose as a threat to some species due to increasing tolerance of human presence. Humans are a threat due to shootings and habitat destruction of rooks.
Known Predators:
Corvus frugilegus is similar in appearance to C. corone (carrion crow), another species of corvid. Though both species are covered in glossy black feathers with a metallic sheen, rooks are distinguishable from carrion crows by their slightly smaller size, distinct wedge-shape tail, light colored bill, and prominently-fingered wingtips. Rooks average 47 cm long and weigh 337 to 531 g, but are considered large when compared to most other corvid species. Rooks show weak sexual dimorphism, with males slightly larger than females. In rooks, wing length ranges from 290 to 330 mm and tarsus length ranges from 52 to 58 mm. For their size, rooks have a relatively large bill (53 to 57 mm long) that tapers to a sharp point. This long, sharp bill aids in food retrieval and eating insects.
Corvus frugilegus frugilegus tends to have a longer, thicker beak than that of C. f. pastinator, as well as a larger area of bare skin covering the forehead, lores (skin between eye and bill on side of head), and gular area (skin that joins lower mandible to neck). Corvus frugilegus frugilegus also has a violet sheen to its black feathers, whereas C. f. pastinator has a greenish sheen. Juveniles of both subspecies are easily recognizable by their brown-toned feathers and fully-feathered face, which does not become bare until their first spring.
Range mass: 337 to 531 g.
Average length: 47 cm.
Range wingspan: 290 to 330 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike; male larger
Not much is recorded on the lifespan of C. frugilegus, but like most Corvidae species, the rook is expected to live 15 to 20 years in the wild. According to the EURING European Longevity Records, the oldest rook found in the wild lived to be 22 years old. As is the trend, rooks in captivity may live for much longer. In a similar species, Corvus corax, the longest lifespan was recorded at 69 years for life in captivity.
Average lifespan
Status: wild: 22 years.
Typical lifespan
Status: wild: 15 to 20 years.
Rooks are widely distributed across Europe and western Asia, preferring arable land, river plains, and steppe regions where soil is generally soft and fertile. In agricultural landscapes, rooks tend to avoid areas where winter cereal grains such as rye and wheat are grown, instead preferring areas in which softer and more easily-accessible spring cereals such as barley are grown. Spring cereals are an ideal food source for C. frugilegus due to easy foraging that results from their small height. River plains and steppe regions also serve as excellent habitats for rooks because their rich soil is usually teeming with insects, and soft ground makes foraging possible. Rooks can also be found in areas bordering cities and towns as long as large trees are available for cover and food is available for scavenging. Given their wide occupation of much of Europe and Asia, rooks are able to tolerate a large elevation range, from sea level to approximately 4000 m.
Range elevation: 0 to 4000 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: savanna or grassland ; forest
Other Habitat Features: suburban ; agricultural ; riparian
Corvus frugilegus is found in the Palearctic region, across much of Europe and Asia. Two subspecies of rooks are recognized: C. f. frugilegus and C. f. pastinator. The geographic range of C. f. frugilegus extends from Ireland eastward across Europe into Russia, with southern boundaries as far as Turkey and Iran. Sporadic, localized populations can be found as far north as southern Sweden, Norway, and Denmark. Populations have also been introduced in New Zealand, where they flourish. During breeding and migration, C. f. frugilegus can be found in northern Russia and the Mediterranean area, respectively. The geographic range of C. f. pastinator, commonly known as the Oriental rook, extends from eastern Asia west into northern Mongolia. The two subspecies are generally geographically separated by the Altai Mountains.
Biogeographic Regions: palearctic (Native ); oceanic islands (Introduced )
Rooks are opportunistic feeders. As omnivores, they eat any edible food item. Due to the strength and size of the bill, rooks are often found probing the ground in search of earthworms or other insects. Rooks also ingest small acorns, small fruits, and cereal grains. When the opportunity arises, rooks prey on small mammals, small birds, carrion, and eggs of the same species. They also have been known to act as “nest predators”, attacking the nests of other species of birds in order to eat the hatchlings and eggs.
Rook feeding habits often vary due to the location of their nest. Unlike those occurring in natural areas as above, those that live near urban sites also act as scavengers and take advantage of trashcans as well as abandoned food. Most rooks spend much of their time foraging at dawn and dusk. Primarily searching at dawn, rooks will pick through garbage bags to obtain food. However, they have been seen foraging during the day. Like all corvids, rooks store their food.
Animal Foods: birds; mammals; eggs; carrion ; insects; terrestrial worms; aquatic crustaceans
Plant Foods: seeds, grains, and nuts; fruit
Foraging Behavior: stores or caches food
Primary Diet: carnivore (Eats terrestrial vertebrates, Eats eggs, Insectivore , Eats non-insect arthropods, Vermivore, Scavenger ); herbivore (Frugivore , Granivore ); omnivore
Rooks have numerous roles in the ecosystem. They serve as hosts for numerous protozoan organisms such as trypanosomes and leucocytozoans. Such organisms are generally not pathogenic and merely occupy rooks as vectors. While rook hosting of these organisms does not directly cause it any harm, it makes infection of other species possible. In this way, rooks sustain the lifecycle of these organisms.
Rooks also serve as hosts for oribatid mites, among other types of mites. Oribatid mites are soil mites, and feed on dead plant and fungal material. These mites live in the feathers of rooks, where it is believed they consume fungi. Such a relationship does not harm rooks, it is actually beneficial, though its results are not readily noticeable.
Lastly, rooks play a key role in seed dispersal as they crack open and consume cereal grains such as barley. Without birds and small animals to crack open seeds and remove them from the plant, seed dispersal for cereal grains could be problematic or less efficient.
Ecosystem Impact: disperses seeds; soil aeration
Mutualist Species:
Commensal/Parasitic Species:
While many farmers claim that C. frugilegus does more harm than good, recent studies suggest that 60 to 90% of insects consumed by rooks are agricultural pests. If this is the case, large numbers of rooks may have some impact on pest insect populations. Rooks are also known to dig into the soil in search of insects, so this may have a slight aeration effect which is particularly important in agricultural environments. Lastly, rooks play an important role in seed dispersal as they consume and crack open cereal grains.
Positive Impacts: controls pest population
Rooks are commonly referred to as "agricultural pests", meaning they cause the loss and destruction of commercial crops. When foraging for food, rooks are often found in farmland crops, taking advantage of the cereals and grains. This can lead to an economic decline for farmers, as well as any person or company that may use the farmer for food. However, rooks are only known to cause damage to crops if the preferred food is not available.
As well as being agricultural pests, rooks that live in urban areas are likely to get into garbage and rip open the bags, which can in turn cause problems for humans.
Negative Impacts: crop pest
Rooks have a distinct call that has been described as sounding like a “caw." When rooks are defending or establishing a territory, multiple “caws” are used. Rooks also have a snarling call, as well as a gull call, which are used when an intruder comes within a short distance of their nest. In order to remain in contact with other rooks, a single loud “caw” is used during both foraging and migration. However, it is believed that rooks mainly vocalize with their mate, rather than in other social interactions. Like other birds, rooks perform singing duets (usually with a mate) that are believed to create a stronger mating bond. Female rooks use frequent vocalizations, by means of a begging call, in order to establish a submissive state with their mate, as well as to show dependency towards the male. Rooks also rely heavily on vocal communication with their young during the first few days of hatching.
Auditory communication is vital to the rook. They have a sense of hearing which helps them distinguish amongst other populations and species. The rook is able to recognize the call of a mate or its young. In addition to vocalizations, rooks also rely on visual communication, which becomes increasingly more important once young are able to open their eyes. Pecking is another form of communication, when an intruder rook comes too close to a territory; pecking attacks can occur usually resulting in the retreat of the intruder.
Communication Channels: visual ; tactile ; acoustic
Other Communication Modes: duets
Perception Channels: visual ; polarized light ; tactile ; acoustic ; chemical
Despite their highly social nature, rooks form pair bonds that lasts from several years to life. Rooks generally take mates when they are two years old. During the fall mating season, pair bonds nest together in communal roosts called rookeries until they return to individual nests to lay eggs. Despite hundreds of birds in a single rookery, rooks maintain their pair bonds through extensive communication. Though rooks are known for being monogamous, like other corvid species such as Corvus corax (common ravens) and C. corone (carrion crows), there have been reported instances of bigamy and occupation of a nest by multiple females.
Mating System: monogamous ; cooperative breeder
Breeding and egg-laying usually begins around late February in Britain, but may be as late as April and May in central Europe and Russia where cold weather persists for a longer period of time. Rooks generally build nests in tall deciduous trees, though nests on the ground and in bushes are not uncommon. Nests consist of sticks and branches with a deep leaf, grass, and moss-lined cup. Rooks (Corvus frugilegus) lay two to seven (average four) blue-green eggs that are covered with brown and grey mottling. Rook eggs are very similar in appearance to those of ravens (C. corax), though slightly smaller, on average 40 mm long. After 16 to 18 days of incubation mainly by the female, the young hatch blind and helpless.
Breeding interval: Rooks breed once yearly.
Breeding season: Breeding occurs in February through May, depending on length of winter.
Range eggs per season: 2 to 7.
Average eggs per season: 4.
Range time to hatching: 16 to 18 days.
Range fledging age: 32 to 33 days.
Average age at sexual or reproductive maturity (female): 2 years.
Average age at sexual or reproductive maturity (male): 2 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
For the 16 to 18 day incubation period the female rook covers the eggs unless she has to briefly leave the nest, in which case the male takes over this duty. After hatching, the female tends to the young exclusively while the male delivers food. This continues for approximately the first ten days until the young become more self-sufficient, at which point the female joins the male in food gathering. At around 32 to 33 days old the young rooks fledge and leave the nest, but roost in nearby trees to remain close to the parents. The young continue their relationship with the parents for several weeks until they become fully independent. Even after reaching full maturity and independence, rooks generally remain members of their original rookery.
Parental Investment: altricial ; male parental care ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female); extended period of juvenile learning
Winter visitor?
http://www.cell.com/current-biology/abstract/S0960-9822(09)01455-9
The rook (Corvus frugilegus) is a member of the family Corvidae in the passerine order of birds. It is found in the Palearctic, its range extending from Scandinavia and western Europe to eastern Siberia. It is a large, gregarious, black-feathered bird, distinguished from similar species by the whitish featherless area on the face. Rooks nest collectively in the tops of tall trees, often close to farms or villages, the groups of nests being known as rookeries.
Rooks are mainly resident birds, but the northernmost populations may move southwards to avoid the harshest winter conditions. The birds form flocks in winter, often in the company of other Corvus species or jackdaws. They return to their rookeries and breeding takes place in spring. They forage on arable land and pasture, probing the ground with their strong bills and feeding largely on grubs and soil-based invertebrates, but also consuming cereals and other plant material. Historically, farmers have accused the birds of damaging their crops, and have made efforts to drive them away or kill them. Like other corvids, they are intelligent birds with complex behavioural traits and an ability to solve simple problems.
The rook was given its binomial name by the Swedish naturalist Carl Linnaeus in 1758 in his Systema Naturae.[2] The binomial is from Latin; Corvus means "raven", and frugilegus means for "fruit-gathering". It is derived from frux or frugis, meaning "fruit", and legere, meaning "to pick".[3] The English-language common name rook is ultimately derived from the bird's harsh call.[4] Two subspecies are recognised; the western rook (C. f. frugilegus) ranges from western Europe to southern Russia and extreme northwestern China, while the eastern rook (C. f. pastinator) ranges from central Siberia and northern Mongolia eastwards across the rest of Asia.[5] Collective nouns for rooks include building, parliament, clamour and storytelling.[6] Their colonial nesting behaviour gave rise to the term rookery.[7]
The rook is a fairly large bird, at 280 to 340 g (9.9 to 12.0 oz) adult weight, 44 to 46 cm (17 to 18 in) in length and 81 to 99 cm (32 to 39 in) wingspan.[8] It has black feathers that often show a blue or bluish-purple sheen in bright sunlight. The feathers on the head, neck and shoulders are particularly dense and silky. The legs and feet are generally black, the bill grey-black and the iris dark brown. In adults, a bare area of whitish skin in front of the eye and around the base of the bill is distinctive, and enables the rook to be distinguished from other members of the crow family. This bare patch gives the false impression that the bill is longer than it is and the head more domed. The feathering around the legs also appears shaggier and laxer than the similarly sized carrion crow, the only other member of its genus with which the rook is likely to be confused.[9] Additionally, when seen in flight, the wings of a rook are proportionally longer and narrower than those of the carrion crow.[10] The average lifespan is six years.[11]
The juvenile plumage is black with a slight greenish gloss, except for the hind neck, back and underparts, which are brownish-black. The juvenile is superficially similar to a young crow because it lacks the bare patch at the base of the bill, but it has a thinner beak and loses the facial feathers after about six months.[9]
At the Cafe, Marwell Zoo
Western rooks are resident in the British Isles and much of north and central Europe but vagrant to Iceland and parts of Scandinavia, where they typically live south of 60° latitude. They are found in habitats that common ravens dislike, choosing open agricultural areas with pasture or arable land, as long as there are suitable tall trees for breeding. They generally avoid forests, swamps, marshes, heaths and moorland. They are in general lowland birds, with most rookeries found below 120 m (400 ft), but where suitable feeding habitat exists, they may breed at 300 m (1,000 ft) or even higher. Rooks are often associated with human settlements, nesting near farms, villages and open towns, but not in large, heavily built-up areas.[9] The eastern subspecies in Asia differs in being slightly smaller on average, and having a somewhat more fully feathered face. In the north of its range the species has a tendency to move south during autumn, and more southern populations are apt to range sporadically.
The species has been introduced into New Zealand, with several hundred birds being released there from 1862 to 1874. Although their range is very localized, the species is now regarded as an invasive pest and is the subject of active control by many local councils.[12] This has wiped out the larger breeding colonies in New Zealand, and the remaining small groups have become more wary.[13]
Rooks are highly gregarious birds and are generally seen in flocks of various sizes. Males and females pair-bond for life and pairs stay together within flocks. In the evening, the birds often congregate at their rookery before moving off to their chosen communal roosting site. Flocks increase in size in autumn with different groups amalgamating and birds congregating at dusk before roosting, often in very large numbers and in the company of jackdaws. Roosting usually takes place in woodland or plantations, but a small minority of birds may continue to roost at their rookery all winter, and adult males may roost collectively somewhere nearby. The birds move off promptly in the morning, dispersing for distances of up to 10 km (6 mi).[9]
Large groups of rooks (in breeding colonies or night roost sites) can contribute to changes in soil properties. The amount of ornithogenic material in these soils is very high.[14]
Foraging mostly takes place on the ground, with the birds striding about, or occasionally hopping, and probing the soil with their powerful beaks. Flight is direct, with regular wingbeats and little gliding while in purposeful flight; in contrast, the birds may glide more extensively when wheeling about in leisure flight near the rookery. In the autumn, flocks sometimes perform spectacular aerial group flights, including synchronised movements and individual antics such as dives, tumbles and rolls.[9]
Examination of stomach contents show that about 60% of the diet is vegetable matter and the rest is of animal origin. Vegetable foods include cereals, potatoes, roots, fruit, acorns, berries and seeds while the animal part is predominantly earthworms and insect larvae, which the bird finds by probing the ground with its strong bill. It also eats beetles, spiders, millipedes, slugs, snails, small mammals, small birds, their eggs and young, and occasionally carrion.[9]
In urban sites, human food scraps are taken from rubbish dumps and streets, usually in the early hours or at dusk when it is relatively quiet. Like other corvids, rooks will sometimes favour sites with a high level of human interaction, and can often be found scavenging for food in tourist areas or pecking open garbage sacks.[15] Rooks have even been trained to pick up litter in a theme park in France.[16]
The male usually initiates courtship, on the ground or in a tree, by bowing several times to the female with drooping wings, at the same time cawing and fanning his tail. The female may respond by crouching down, arching her back and quivering her wings slightly, or she may take the initiative by lowering her head and wings and erecting her partially spread tail over her back.[9] Further similar displays are often followed by begging behaviour by the female and by the male presenting her with food, before coition takes place on the nest. At this stage, nearby male rooks often mob or attack the mating pair, and in the ensuing struggle, any male that finds himself on top of the female will attempt to copulate with her. She terminates these unwanted advances by exiting the nest and perching nearby.[17] A mated pair of rooks will often fondle each other's bills, and this behaviour is also sometimes seen in autumn.[9]
Nesting in a rookery is always colonial, usually in the very tops of large trees, often on the remnants of the previous year's nest. In hilly regions, rooks may nest in smaller trees or bushes, and exceptionally on chimneys or church spires. Both sexes participate in nest-building, with the male finding most of the materials and the female putting them in place. The nest is cup-shaped and composed of sticks, consolidated with earth and lined with grasses, moss, roots, dead leaves and straw.[9] Small branches and twigs are broken off trees, though as many are likely to be stolen from nearby nests as are collected direct, and the lining material is also often taken from other nests.[15]
Eggs are usually three to five in number (sometimes six and occasionally seven) and may be laid by the end of March or early April in Britain, but in the harsher conditions of eastern Europe and Russia, it may be early May before the clutch is completed.[15] The background colour is bluish-green to greyish-green but this is almost completely obscured by the heavy blotching of ashy grey and brown. The eggs average 40.0 by 28.3 millimetres (1.57 in × 1.11 in) in size.[9] They are incubated for 16–18 days, almost entirely by the female who is fed by the male. After hatching, the male brings food to the nest while the female broods the young. After ten days, she joins the male in bringing food, which is carried in a throat pouch. The young are fledged by the 32nd or 33rd day but continue to be fed by the parents for some time thereafter. There is normally a single clutch each year, but there are records of birds attempting to breed in the autumn.[9]
In autumn, the young birds of the summer collect into large flocks together with unpaired birds of previous seasons, often in company with jackdaws. It is during this time of year that spectacular aerial displays are performed by the birds. The species is monogamous, with the adults forming long-term pair bonds. Partners often support each other in agonistic encounters and a bird may return to its partner after a quarrel where bill twining, an affiliative behaviour, may take place.[18]
The call is usually described as caw or kaah, and is somewhat similar to that of the carrion crow, but less raucous. It is variable in pitch and has several variants, used in different situations. The call is given both in flight and while perched, at which time the bird fans its tail and bows while making each caw. Calls in flight are usually given singly, in contrast to the carrion crow's, which are in groups of three or four. Other sounds are made around the rookery; a high-pitched squawk, a "burring" sound and a semi-chirruping call. Solitary birds occasionally "sing", apparently to themselves, uttering strange clicks, wheezes and human-like notes; the song has been described as a "base or guttural reproduction of the varied and spluttering song" of starlings.[9]
Although outside of captivity rooks have not shown probable tool-use, captive rooks have shown the ability to use and understand puzzles. One of the most commonly tested puzzles is the Trap-Tube Problem. Rooks learned how to pull their reward out of the tube while avoiding a trap on one side.[19][20]
In captivity, when confronted with problems, rooks have been documented as one of several species of birds capable of using tools as well as modifying tools to meet their needs.[21] Rooks learned that if they push a stone off a ledge into a tube, they will get food. The rooks then discovered they could find and bring a stone and carry it to the tube if no stone was there already. They also used sticks and wire, and figured out how to bend a wire into a hook to reach an item.[22] Rooks also understood the notion of water levels. When given stones and a tube full of water with a reward floating, they not only understood that they needed to use the stones but also the best stone to use.[23]
In one set of experiments, rooks managed to knock a reward off a platform by rolling a stone down a tube toward the base of the platform. Rooks also seemed to understand the idea that a heavier stone will be more likely to knock the platform over. In this same test, rooks showed they understood that they needed to pick a stone of a shape that would roll easily.[21]
Rooks also show the ability to work together to receive a reward. In order to receive a reward, multiple rooks had to pull strings along the lid of a box in order for it to move and them to reach the reward. Rooks seem to have no preference regarding working as a group comparative to working singly.[24]
They also seem to have a notion of gravity, comparable to a six-month-old baby and exceeding the abilities of chimpanzees.[25] Although they do not use tools in the wild, research studies have demonstrated that rooks can do so in cognition tests where tools are required, and can rival, and in some circumstances outperform, chimpanzees.[26]
Farmers have observed rooks in their fields and thought of them as vermin. After a series of poor harvests in the early 1500s, Henry VIII introduced a Vermin Act in 1532 "ordeyned to dystroye Choughes (i.e. jackdaws), Crowes and Rokes" to protect grain crops from their predations. This act was only enforced in piecemeal fashion, but Elizabeth I passed the Act for the Preservation of Grayne in 1566 that was taken up with more vigour and large numbers of birds were culled.[27]
Francis Willughby mentions rooks in his Ornithology (1678): "These birds are noisome to corn and grain: so that the husbandmen are forced to employ children, with hooting and crackers, and rattles of metal, and, finally by throwing of stones, to scare them away."[28] He also mentions scarecrows "placed up and down the fields, and dressed up in a country habit, which the birds taking for countrymen dare not come near the grounds where they stand".[28] It was some time before more observant naturalists like John Jenner Weir and Thomas Pennant appreciated that in consuming ground-based pests, the rooks were doing more good than harm.[28]
Rookeries were often perceived as nuisances in rural Britain, and it was previously the practice to hold rook shoots where the juvenile birds, known as "branchers", were shot before they were able to fly. These events were both a social occasion and a source of food (the rook becomes inedible once mature) as rook and rabbit pie was considered a delicacy.[29]
Rooks have a wide distribution and large total population. The main threats they face are from changes in agricultural land use, the application of seed dressings and pesticides, and persecution through shooting. Although total numbers of birds may be declining slightly across the range, this is not at so rapid a rate as to cause concern, and the International Union for Conservation of Nature has assessed the bird's conservation status as being of "least concern".[1]
The rook (Corvus frugilegus) is a member of the family Corvidae in the passerine order of birds. It is found in the Palearctic, its range extending from Scandinavia and western Europe to eastern Siberia. It is a large, gregarious, black-feathered bird, distinguished from similar species by the whitish featherless area on the face. Rooks nest collectively in the tops of tall trees, often close to farms or villages, the groups of nests being known as rookeries.
Rooks are mainly resident birds, but the northernmost populations may move southwards to avoid the harshest winter conditions. The birds form flocks in winter, often in the company of other Corvus species or jackdaws. They return to their rookeries and breeding takes place in spring. They forage on arable land and pasture, probing the ground with their strong bills and feeding largely on grubs and soil-based invertebrates, but also consuming cereals and other plant material. Historically, farmers have accused the birds of damaging their crops, and have made efforts to drive them away or kill them. Like other corvids, they are intelligent birds with complex behavioural traits and an ability to solve simple problems.
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