Andrew,
Crows are very social animals.  They live in family groups during the breeding season,
with a multi-year learning period, and young birds raised the previous year often help
their parents to raise their younger siblings.  In the non-breeding season crows gather into
massive roosting congregations in the late afternoon.  In recent years these roosts have
been much more conspicuous to people as the birds have chosen urban areas with large
trees.  In the morning they commute to farm fields to search for waste corn or to dumps
(or the Cornell food services composting facility) for waste food.  Toward March and the
onset of breeding season the roost breaks up and the birds return to their family territories. 
I think some local birds here retain residency in their territories during winter as well.  Those
winter roosts are amazing, just to consider all the biomass, and the area over which they
must be feeding.  Their socializing is noisy and active before and after their actual sleeping
time and includes areas outside the actual roost.  They are harmless, of course, but people
whose knowledge of biology extends only to Alfred Hitchcock movies may be unnerved. 
And people whose possessions are underneath roost trees with hundreds of birds will be
understandably unhappy with the birds' defecation.  I like to watch the flocks' swirling flight.
Kevin McGowan has been studying crows in this area for years, and I hope he will expand
upon (and if necessary correct) this post.  His project is responsible for the crows with
various colored wing tags, each color representing a different year.  Most crows are tagged
in the nest before they are old enough to leave.  Each bird's tags has a 2-digit code, and
if you tell Kevin which bird you have seen when and where, he may return the favor with
a brief life history of that individual. 
--Dave Nutter



On Dec 15, 2010, at 07:05 PM, Andrew Roe <andrew.walker....@gmail.com> wrote:

This is only my second winter in Ithaca (I'm a grad student, here from the southeast) so I don't really know how normal this is- but there seem to be an ENORMOUS number of crows around downtown Ithaca and Cornell- swirling at dusk, covering roofs, nearly toppling trees, blotting out the sun, etc.

Can someone in the know let me know what's going on? Are these all birds passing through, or is there some sort of monumental attack on the Lab of O in the works?

Thanks,

Andrew

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