Crow Roosts – Huge Flocks of Crows
These Birds Sleep Together in Trees in Fall and Winter
Dec 21, 2008 Rosemary Drisdelle
Beginning in fall as the days draw in, crows do something strange and interesting: birds that forage over a large area during the day come together to spend the night in a communal roost. Crow populations are high in many areas, and roosts of a million birds have been reported.
They begin to gather about an hour before sunset. Single birds, small flocks and sometimes long lines of hundreds or thousands of birds converge on a particular area.
Where Do Crows Roost?
Crows in North America used to roost in the countryside but, beginning in the ‘60s, and increasingly through the ‘70s and ‘80s, they moved into cities. They choose both evergreen and deciduous trees, often clumps of trees surrounded by open spaces. To find a crow roost, watch for birds at sundown and follow them.
What Does a Crow Roost Look Like?
Before going to roost, crows typically congregate in staging areas nearby. It’s a noisy gathering and the birds mill about, calling continuously and rearranging themselves. As full darkness approaches, they move to the roost where they can occupy a tree so thickly that it appears to be leafed out in shiny black.
Through the night, the roost is fairly quiet, but the clamor begins again as sunrise approaches and the birds leave in groups to begin the day’s foraging.
Why Do Crows Roost Together?
We’re not sure why crows form such enormous roosts in fall and winter, but there may be a number of reasons:
- Safety—a sleeping crow is much safer in a large gathering than alone or with just a few others. This may also be the reason crows have moved into cities: better visibility, fewer predators and relative safety even from people. Interestingly, it’s thought that family members spread out rather than roosting side by side, increasing the survival potential of the smaller group.
- Warmth.
- To communicate—crows warn each other of danger and lead others to food sources. Roosts may be a means of efficiently passing along information.
- To find friends and mates—migrants new to the community and unmated young birds may learn the territory, learn to socialize, and find partners at the roost.
Nuisance Crow Roosts
When a crow roost is located in a human community, it’s not always welcome. The roost is a messy place, with bird droppings coating everything from the treetops down, and the tremendous noise made by arriving and departing birds can be very disturbing to light sleepers. It does no good to just wait for the birds to move on: some roosts are used for centuries.
Communities have tried everything from trying to kill all the crows, to cutting down all the trees in the roost, to deterrence with noise, netting, strips of tape tied to branches etc. These measures typically don’t work very well, with the roost becoming reestablished in the same location or nearby relatively quickly.
If a crow roost is really intolerable, it may be possible to use deterrence methods to relocate the birds to a more convenient place, but the ideal solution is to appreciate having this wonderful, gregarious, interesting, natural phenomenon in the neighborhood, and enjoy the crows.
Additional Reading
Ralph, an Unforgettable Pet Crow
A Birding Itinerary That Visits a Crow Roost
Sources
“A Murder of Crows” Dube, Rebecca. The Glove and Mail, Friday Dec 14, 2007.
“Urban Crow Roosts in California.” Gorenzel, W. Paul and Terrell P. Salmon. Proceedings of the Fifteenth Vertebrate Pest Conference 1992, University of Nebraska – Lincoln. digitalcommons.unl.edu
In the Company of Crows and Ravens. Marzluff, John M., Tony Angell. New Haven: Yale University Press, 2007
Evergreens and Darkness Hide Most of the Crows
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Crows at Dawn
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