crow city | crow family | carrion & hooded crow | rook | jackdaw | magpie | jay | chough | raven
The carrion and hooded crows are likely to have evolved from the same fairly recent ancestor but in isolation from each other during an Ice Age, later stretching into the newly accessible country, eventually sharing lands. They are of the same size and can interbreed, resulting in birds of mixed plumage.
The carrion crow is black with a bluey purple or blue gloss, the gloss greener on the wings and tail. The bill, legs and claws are all black and their eyes are a dark brown. The hooded crow is black but with a pale ash grey hood or cloak on the back of the neck, mantle, scapulars, back, rump, lower breast, abdomen, flanks, axillaries and under tail coverts. Both crows are found in Britain, the carrion crow seeming fonder of upland areas than the hooded crow.
The hooded crow is unlikely to be confused with other crows close up because of its grey markings, but both crows are easily distinguished from the rook by their calls, their squarer tails, broader wings and slower wingbeat. The crow bill is heavier. When perched the crows will frequently flick up their closed wings, which rooks and ravens but rarely do.
British crows do not migrate. They are not so adversely affected by the winter cold since they can feed upon the bodies of those who have fallen to its touch. They do prefer country where trees abound and will nest in denser woods than will the rook. The crow doesn’t favour bare mountainous land or treeless desert the way the raven does but is an adaptable creature and will nest on the ground if necessary, notably in the Shetlands. They will also nest in electricity pylons in country where there are no suitable trees.
Crows cannot breed without their own territory. This causes unmated crows to help with the raising of young of another pair, often the new brood of their own parents. All members of a brood will stay with their parents for the same amount of time, at the end of which they will away to join the flock. During the mating season the breeding birds are at threat from other crows with an eye on their territory, who will attempt to eat eggs, kill young and generally chase the pair from the territory. During these altercations the male crows always fight with other male crows and the females similarly with birds of their own gender.
Outside of the mating season, communal roostings are tolerated within a territory. The birds will gather at pre roost assemblies before leaving for the roost, which is often shared with other members of the crow family, the different species tending to have their own part of the roost, most normally a thickly leaved tree.
Holyoak (1968) examined the gizzards of 234 carrion crows from an agricultural area in South England. He found the following foodstuffs to be favoured:
| Vegetable | ||
| grain ** | cherries | plums |
| wild plant seeds ** | potatoes | acorns |
| apples and pears | beechnuts | walnuts |
| Animal | |
| live small mammals ** | carrion * |
| earthworms | grassland and woodland insects |
| live adult birds | nestling birds |
| birds’ eggs | fish carrion |
| molluscs | littoral invertebrates |
| spiders | woodlice |
| centipedes | ticks |
| bread | animal food stuffs |
When feeding on the ground, female crows tend to turn clods with their feet whilst male crows prefer to probe with their bills. When dropping shellfish to crack their shells, crows have been observed to always do so on to hard ground, unlike gulls, who will sometimes drop on to soft ground by accident. Crows will take live fish out of running water and pick off dead ones from the surface.
Dr Houston sought to ascertain the effect of crows on hill sheep farming. He found that almost all the couped ewes (if the fleece is too heavy, the sheep cannot right itself if it has fallen on its back) who were attacked by crows were already dead due to their prone position before the shepherd came along, raising the possibility that the crows had simply been taking carrion. His studies also revealed that only one lamb in seventeen hundred is killed by crows. So although the collective noun for a group of crows is a murder, this upon investigation would appear to be unfair to the birds’ nature and habits.
The main predator of crows - except for other crows during breeding - is man. Birds of prey will occasionally take a crow but risk mobbing if they do so by other crows.
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