This is very helpful information! Thank you so much for the complete picture. I am learning so much from being on this list serve. I am very grateful! Sue Rakow
On Tue, Mar 4, 2014 at 8:26 AM, Anne Clark <anneb.cl...@gmail.com> wrote: > These groups are "winter roosts", and they are nothing new in crow life. > Despite what urban residents sometimes think, crows didn't start gathering > when we set out cities for them to use. Roosting in groups at any time of > year may offer safety in numbers from night predators, such as Great Horned > Owls. > > In winter, birds living in northern areas that usually have constant snow > cover for months do migrate south--Canada, areas of New England. Crows > don't necessarily have a particular area they migrate TO. They may go as > far as an area that is usually ok for foraging, perhaps one that they are > familiar with from previous migrations. There they form flocks that are > made up of migrants as well as wide-foraging locals. If it gets unusually > snowy and cold, they may move further south. (We really don't know much of > the repeat migratory routes of individual crows. We do know that birds > tagged in Ithaca in winter are then seen on territories in Canada, VT, New > Hampshire in summer, and that some birds RAISED in Ithaca have been > observed or shot in winter, in such places as Maryland, West VA, and > Pennsylvania, as well as in Cortland, Auburn, Geneva) > > In the winter flocks, birds are foraging in open fields and off familiar > areas. During foraging, flocks offer some safety in numbers to detect > predators in day (hawks, hunters, whatever). At night the flocks "flock > up" still more in places that offer "good roosting sites", which probably > includes wind breaks, places from which owls can be detected at night. So > they are probably gathering both for safety in numbers and also because > they all agree on what makes a good site. Cities may offer fewer > predators, but also the lights may allow them to see the predators. > Finally roosting in flocks that include birds that have sampled food > sources widely may allow birds to find new food sources, perhaps by > following the most assured and directed birds leaving the roost. > > So--Upstate NY has its own crows and is ideally positioned for northern > crows--so flocks become big. They like the agricultural fields > interspersed with trees and lots of running water sources (which may be > important in cold winters)...and we also offer lots of smaller cities, with > large groups of lit trees in their downtowns or college campuses. These > seem to be attractive. > > Mid-late March is the start of the breeding season and flocking crows will > be returning to their breeding latitudes. Our Ithaca pairs are already > calling on territory during daytimes. > > As I say, some of this story is surmised from the patterns, not pinned > down with hard data on individuals! We know what our tagged birds do, when > we can follow them. But we would love to have gps data coming in from our > birds, such as the snowy owls and golden eagles give their researchers. > Bring on the Tiny Tags! > > Anne > > On Mar 4, 2014, at 7:19 AM, Sue Rakow wrote: > > I observed the murder of crows on Sunday evening. It was stunning. I would > like to know more about why they gather in such large groups. Are they on > the move or are they local? Can anyone help me understand? > Thanks. > Sue Rakow > -- > *Cayugabirds-L List Info:* > Welcome and Basics <http://www.northeastbirding.com/CayugabirdsWELCOME> > Rules and Information <http://www.northeastbirding.com/CayugabirdsRULES> > Subscribe, Configuration and > Leave<http://www.northeastbirding.com/CayugabirdsSubscribeConfigurationLeave.htm> > *Archives:* > The Mail > Archive<http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html> > Surfbirds <http://www.surfbirds.com/birdingmail/Group/Cayugabirds> > BirdingOnThe.Net <http://birdingonthe.net/mailinglists/CAYU.html> > *Please submit your observations to eBird > <http://ebird.org/content/ebird/>!* > -- > > > -- Cayugabirds-L List Info: http://www.NortheastBirding.com/CayugabirdsWELCOME http://www.NortheastBirding.com/CayugabirdsRULES http://www.NortheastBirding.com/CayugabirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/Cayugabirds 3) http://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
