NATURE IN CONTROL
Information about the birds classed as Corvids
What is a Corvid this video may help?
Corvidae is a cosmopolitan family of oscine passerine birds that contains the crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs, and nutcrackers. In common English, they are known as the crow family, or, more technically, corvids. Over 120 species are described. The genus Corvus, including the jackdaws, crows, rooks, and ravens, makes up over a third of the entire family. Corvids are the largest passerines.
Corvids display remarkable intelligence for animals of their size and are among the most intelligent birds thus far studied. Specifically, members of the family have demonstrated self-awareness in mirror tests (European magpies) and tool-making ability (e.g. crows and rooks), skills which until recently were thought to be possessed only by humans and a few other higher mammals. Their total brain-to-body mass ratio is equal to that of non-human great apes and cetaceans, and only slightly lower than that of humans.
They are medium to large in size, with strong feet and bills, rictal bristles, and a single moult each year (most passerines moult twice). Corvids are found worldwide except for the tip of South America and the polar ice caps. The majority of the species are found in tropical South and Central America and in southern Asia, with fewer than 10 species each in Africa and Australasia. The genus Corvus has re-entered Australia in relatively recent geological prehistory, with five species and one subspecies there. Several species of raven have reached oceanic islands, and some of these species are now highly threatened with extinction or have already become extinct.
The legal status of corvids in the UK
Crows, Jackdaws and Rooks are protected under the Wildlife & Countryside Act 1981 and the Wildlife (Northern Ireland) Order 1985. This makes it illegal to intentionally take, injure or kill them, or to take, damage or destroy an active nest or its contents. However, the law recognises that in some circumstances control may be necessary. The UK Government issues annually a general licence (for which it is not necessary to apply individually) under the Wildlife and Countryside Act, which allows certain corvids to be killed or taken by ‘authorised persons’, using permitted methods, for the purposes of:
• preventing serious damage to agricultural crops or livestock
• preserving public health/air safety
• conserving wild birds.
The killing can only be done under these specific conditions. An ‘authorised person’ is a landowner or occupier, or someone acting with the landowner’s or occupier’s permission.
Legal control methods involve trapping or shooting. Larsen traps, a type of cage trap, are designed to catch birds alive and unharmed, and it can be baited with food, or with a live decoy crow, jackdaw or rook (providing this decoy is provided with adequate food and water). If you suspect that a Larsen trap has been set illegally to catch birds of prey, please report this
to the police Wildlife Crime Officer. Gun laws state that control by shooting can only be done well away from houses and public roads.
The RSPB is not opposed to legal, site-specific control, nor to the legal use of Larsen traps. The RSPB opposes illegal corvid control, such as poisoning, which has a high risk of accidentally poisoning other birds, including rare birds of prey. Many people wish to control crows and jackdaws in gardens, thinking that they are a threat to small garden birds. Considering that there is no scientific evidence that either species would pose a conservation problem to any species of garden bird, the RSPB believes that the use of general licence in
this context is at best debateable. Where rooks choose to nest in suburban areas or in trees in gardens, people are often intolerant of their presence either because of the noise, or because they have parked a car underneath the nesting trees and it has received the inevitable scattering of droppings.
These situations constitute a nuisance, which is not a legal reason to kill any bird or destroy its active nest. Sometimes a large quantity of droppings may be viewed as a health hazard. It is advisable to obtain the opinion of a public health officer before any action is taken to ensure that the action is lawful. In those situations where there is a genuine problem,
deterrents that prevent the birds from settling to breed in the first place are far preferable to destroying nests. It must be remembered that if challenged, anyone killing birds may have to prove to a court of law that they had acted lawfully.
Rook is a fairly large bird, at 45 to 47 cm (18 to 19 in) in length, with 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. Additionally, when seen in flight, the wings of a rook are proportionally longer and narrower than those of the carrion crow.
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.
Carrion Crow The plumage of the carrion crow is black with a green or purple sheen, much greener than the gloss of the rook. The bill, legs and feet are also black. It can be distinguished from the common raven by its size (48–52 cm or 19 to 20 inches in length as compared to an average of 63 centimetres (25 inches) for ravens) and from the hooded crow by its black plumage. The carrion crow has a wingspan of 84–100 cm or 33 to 39 inches and weighs 400–600 grams.
There is frequent confusion between the carrion crow and the rook, another black corvid found within its range. The beak of the crow is stouter and in consequence looks shorter, and whereas in the adult rook the nostrils are bare, those of the crow are covered at all ages with bristle-like feathers. As well as this, the wings of a carrion crow are proportionally shorter and broader than those of the rook when seen in flight.
Hooded Crow Except for the head, throat, wings, tail, and thigh feathers, which are black and mostly glossy, the plumage is ash-grey, the dark shafts giving it a streaky appearance. The bill and legs are black; the iris dark brown. Only one moult occurs, in autumn, as in other crow species. The male is the larger bird, otherwise the sexes are alike. Their flight is slow and heavy and usually straight. Their length varies from 48 to 52 cm (19 to 20 in). When first hatched, the young are much blacker than the parents. Juveniles have duller plumage with bluish or greyish eyes and initially a red mouth. Wingspan is 98 cm (39 in) and weight is on average 510 g.
The western jackdaw (Coloeus monedula), also known as the Eurasian jackdaw, European jackdaw, or simply jackdaw, is a passerine bird in the crow family. Found across Europe, western Asia and North Africa, it is mostly resident, although northern and eastern populations migrate south in winter. Four subspecies are recognised, which mainly differ in the colouration of the plumage on the head and nape. Linnaeus first described it formally, giving it the name Corvus monedula. The common name derives from the word jack, denoting "small", and daw, a less common synonym for "jackdaw", and the native English name for the bird.
Measuring 34–39 centimetres (13–15 in) in length, the western jackdaw is a black-plumaged bird with a grey nape and distinctive pale-grey irises. It is gregarious and vocal, living in small groups with a complex social structure in farmland, open woodland, on coastal cliffs, and in urban settings. Like its relatives, jackdaws are intelligent birds, and have been observed using tools. An omnivorous and opportunistic feeder, it eats a wide variety of plant material and invertebrates, as well as food waste from urban areas. Western jackdaws are monogamous and build simple nests of sticks in cavities in trees, cliffs, or buildings. About five pale blue or blue-green eggs with brown speckles are laid and incubated by the female. The young fledge in four to five weeks.
Raven a mature common raven ranges between 54 and 67 cm (21" and 26") long, with a wingspan of 115 to 150 cm (45–51"). Recorded weights range from 0.69 to 2 kg (1.5 to 4.4 lb), thus making the common raven one of the heaviest passerines. Birds from colder regions such as the Himalayas and Greenland are generally larger with slightly larger bills, while those from warmer regions are smaller with proportionally smaller bills. A representative of the size variation in the species, ravens from California weighed an average of 784 g (1.728 lb), those from Alaska weighed an average of 1,135 g (2.502 lb) and those from Nova Scotia weighed an average of 1,230 g (2.71 lb). The bill is large and slightly curved, with a culmen length of 5.7 to 8.5 cm (2.2 to 3.3 in), easily one of the largest bills amongst passerines (perhaps only the thick-billed raven has a noticeably larger bill). It has a longish, strongly graduated tail, at 20 to 26.3 cm (7.9 to 10.4 in), and mostly black iridescent plumage, and a dark brown iris. The throat feathers are elongated and pointed and the bases of the neck feathers are pale brownish-grey. The legs and feet are good-sized, with a tarsus length of 6 to 7.2 cm (2.4 to 2.8 in). Juvenile plumage is similar but duller with a blue-grey iris.
Apart from its greater size, the common raven differs from its cousins, the crows, by having a larger and heavier black beak, shaggy feathers around the throat and above the beak, and a wedge-shaped tail. Flying ravens are distinguished from crows by their tail shape, larger wing area, and more stable soaring style, which generally involves less wing flapping. Despite their bulk, ravens are easily as agile in flight as their smaller cousins. In flight the feathers produce a creaking sound that has been likened to the rustle of silk. The voice of ravens is also quite distinct, its usual call being a deep croak of a much more sonorous quality than a crow's call. In North America, the Chihuahuan raven is fairly similar to the relatively small common ravens of the American southwest and is best distinguished by the still relatively smaller size of its bill, beard and body and relatively longer tail. All-black carrion crow (C. corone) in Europe may suggest a raven due to their largish bill but are still distinctly smaller and have the wing and tail shapes typical of crows.
In the Faroe Islands, a now extinct colour-morph of this species existed, known as the pied raven.
White ravens are occasionally found in the wild. Birds in British Columbia lack the pink eyes of an albino, and are instead leucistic, a condition where an animal lacks any of several different types of pigment, not simply melanin.
Common ravens have a wide range of vocalizations which are of interest to ornithologists. Gwinner carried out important studies in the early 1960s, recording and photographing his findings in great detail. Fifteen to 30 categories of vocalization have been recorded for this species, most of which are used for social interaction. Calls recorded include alarm calls, chase calls, and flight calls. The species has a distinctive, deep, resonant prruk-prruk-prruk call, which to experienced listeners is unlike that of any other corvid. Its very wide and complex vocabulary includes a high, knocking toc-toc-toc, a dry, grating kraa, a low guttural rattle and some calls of an almost musical nature.
Like other corvids, ravens can mimic sounds from their environment, including human speech. Non-vocal sounds produced by the common raven include wing whistles and bill snapping. Clapping or clicking has been observed more often in females than in males. If a member of a pair is lost, its mate reproduces the calls of its lost partner to encourage its return.