The family Corvidae includes Crows, Ravens, Jays, Pies, Nutcrackers and Choughs.
They are the largest of the Passerine birds.
The genus Corvus (also known as the Crow genus) narrows the family down to the Raven, Carrion and Hooded Crows, Rook and Jackdaw.
The 'usual' raven is Corvus corax. There are others, such as the Tasmanian Raven, Corvus tasmanicus.
The 'common crow', or carrion crow, has different varieties between continents.
The Eurasian carrion crow is Corvus corone, the American is Corvus brachyrhyncos. I prefer the Eurasian, if only because I can remember it.
Many Corvidae have iridescent plumage. The Magpie, Pica pica, has a boldly contrasting iridescent black and white plumage. In good light, the Raven's black plumage can be seen to have an iridescence. Crows have a greenish gloss, whereas rooks have a reddish-purple tinge. These iridescent colours are produced by broad, flat feather barbles with blunt ends. The broad surfaces often overlap one another like the horizontal laths of a closed venetial blind, giving the feathers a smooth, satin-like surface. There may be various colours which are caused by the interference of light waves reflected from the outer surfaces of the barbules. This is the type of coloration seen in oil films on water and roads. (Which amused me since I'd always claimed "oily blue-black" to be a corvide colour.)
The Corvid nasal chambers are directly connected to the mouth and nostrils, enabling them to smell food while in the mouth. Handy for detecting and rejecting tainted meat.
Mating among the Corvidae entails a long and continued courtship. The sexes look alike; they have cloacal* intercourse, and are mostly monogamous. Their family life is exceptionally united and protective. They are nearly all single brooded and the female usually broods and incubates.
Man destroys a high proportion of Corvine nests+ and is responsible for many eggs failing to hatch.
Research teams in America, Germany and Russia have reached the conclusion that many birds, especially the Crow family, tend to be quicker on the uptake than 'higher mammals', such as cats, dogs, monkeys etc. (Hah)
Konrad Lorenz claims that, contrary to folklore, corvids are averse to pecking out the eyes of the living (but very quick to go for the eyes of carrion).
Contrary to the beliefs of ornament and toy manufacturers, most crows don't have yellow beaks and feet. If you know anyone who manufactures such things, slap them and tell them to label the thing 'blackbird'.
The Chough bears the splendid scientific name 'Pyrrhocorax'. Possibly (but this is my own conjecture) a flame reference because they have red beak and feet. (Not yellow, so don't go getting any stupid ideas, toy manufacturers). (Apparently flame (pyro) is not the derivation, but, more likely, pyrrhic; in poetry referring to a metrical foot having two short or unaccented syllables - perhaps Pyrrhocorax makes such a noise? Or from the greek purrikhios which refers to a war dance - perhaps the bird stamping for worms? Never seen one myself, so I couldn't tell. Perhaps it has no derivation at all, and is just random naming.)
Contrary to popular belief (Common belief, anyway. It's not popular with me), whilst Corvidae do consume large quantities of grain, they more than offset this by eating corn-eating pests and weed-seeds from arable land. So farmers, save your shotgun cartridges for shooting locusts or something.
They also do other things farmers might appreciate, killing smaller mammals (rabbits and rodents), dispensing with carrion and preventing sheep and deer from becoming infested with blowflies. Jackdaws perch on sheep and delouse them. And, most importantly, they look good.
Much of this information gleaned from the informative, entertaining, and, most importantly, good-looking book "Crows, Jays, Ravens and their relatives" by Sylvia Bruce Wilmore, ISBN 0 7153 7428 1 (Great Britain), published by Douglas David & Charles Limited.
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*cloacal : in this context, non-penetrative. (They actually breed by phone-sex)
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