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Old Friday 4th August 2017, 13:41   #1
satyachil
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Crows: why have they not pushed all other urban birds out?

Theoretical question and not sure if this is the right place for it.
Crows are intelligent, reasonably good fliers (hence mobbers, pursuers, hunters), mid sized (for the bird world), aggressive (i have seen crows snatch pigeon hatchlings, rats and even try picking up small piglets), omnivorous and superbly adapted to urban settings.
So i was wondering why is it that we can still see a fair variety of other bird species in urban areas.
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Old Friday 4th August 2017, 14:11   #2
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Crows are nice easy dinners for medium-large raptors - Goshawks will take adults easily, Buzzards will raid their nests. That helps keep crow numbers down a bit (provided the raptors are allowed to live, which sadly they usually aren't in Britain).
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Old Friday 4th August 2017, 14:21   #3
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well, crows can't nest in the tight spaces used by starlings, sparrows, house finches, wrens, and other small birds And they're too big to feed efficiently on small seeds or small insects the way those birds do. So those small birds will always have a place to live and food to eat, there's no way they will vanish.

Around here, crows nest and roost in trees; they don't do very well in dense cities. Your house crows and European jackdaws are comfortable roosting on rooftops, but they still like trees to nest in. this means they aren't competing directly for nest sites with pigeons. I assume that the presence of crows does diminish pigeon numbers since they do compete somewhat for food, and crows can raid pigeon nests.

Pigeons are fairly intelligent, excellent fliers, mid-sized, nearly omnivorous, and better adapted than crows to urban settings. Why not ask how crows can survive?
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Old Friday 4th August 2017, 14:22   #4
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Understood. In many Indian cities, the only common raptor is the Black Kite. I havent seen the Black Kite preying on Crows. Crows are ubiquitous here. But i also see a lot of smaller birds such as common myna's, sparrows, coppersmith barbets and sunbirds apart from Rock pigeons. I would have expected the Crows to raid the nests of the smaller birds and perhaps exterminate them from cities.

@nartreb I didnt see your response before posting this.
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Old Friday 4th August 2017, 14:29   #5
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I'm sure they would if they could. I don't know your local small birds but I bet most of them nest in small holes where the crows can't reach. (e.g. common myna's only about a third of the size of a house crow, by weight, and guess what? They're cavity nesters.)
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Old Saturday 5th August 2017, 04:54   #6
satyachil
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Originally Posted by nartreb View Post
I'm sure they would if they could. I don't know your local small birds but I bet most of them nest in small holes where the crows can't reach. (e.g. common myna's only about a third of the size of a house crow, by weight, and guess what? They're cavity nesters.)
i believe this might be a big part of the explanation.
Indeed common mynas, sparrows, coppersmith barbets are all typically cavity nesters. Sunbirds do make pouch like nests with leaves, twigs etc.
thanks !
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Old Monday 11th September 2017, 05:21   #7
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Originally Posted by Nutcracker View Post
Crows are nice easy dinners for medium-large raptors - Goshawks will take adults easily, Buzzards will raid their nests. That helps keep crow numbers down a bit (provided the raptors are allowed to live, which sadly they usually aren't in Britain).
Interesting about the Goshawk. We have many Carrion Crows here in Lincolnshire on the farm and they are boss of the half dozen or so Buzzards, successfully mobbing them out of harms way.
The Carrion is a big old bird and quite strong. I have seen about ten of them on the ground all with their wings outstretched rounding up a young rabbit. It would be a brave Goshawk to take on a team like that though I could imagine it could take out the odd individual on its own.

We had a good example the other year of the old adage "Big fleas have little fleas, upon their backs to bitem, little fleas have lesser fleas and so ad infinitum"
The Carrions had been mobbing some Buzzards who eventually went away but were seen soon afterwards dive bombing an Osprey. The Buzzards are rather clumsy flyers compared to the Osprey and their attempts to intimidate were shrugged off easily by the Osprey who hardly seemed to flex his wings to move out of the Buzzard's way. The Buzzard's dive ended in an undignified flapping to gain enough height for another attack.
Eventually the Osprey tired of this little irritation and on the next attack he rolled on his back in mid flight and showed them his talons! That was warning enough for the Buzzards who gave up!
I managed to record it all on video.
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Old Monday 11th September 2017, 06:32   #8
ChrisKten
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Quote:
Originally Posted by jack harnser;3614890[...
The Carrion is a big old bird and quite strong. I have seen about ten of them on the ground all with their wings outstretched rounding up a young rabbit. It would be a brave Goshawk to take on a team like that though I could imagine it could take out the odd individual on its own.

[...]
A Goshawk is a big powerful bird with powerful feet/toes and large(ish), sharp talons. Also, another clue as to why a Crow poses no problems is in the weight and wingspan of both species... especially the female Goshawks:

Goshawk wingspan - 100-150 cm (40-60")
Carrion Crow wingspan - 93-104 cm (37-42")

Goshawk weight - 500-1450 g (1-3¼ lb)
Carrion Crow weight - 370-650 g (¾-1½)


So a female Goshawk is about twice the weight with perhaps 18" extra wingspan.
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