Why do crows congregate (roost) in large numbers?
For crows, large roosts are primarily a fall and winter phenomenon. Numbers peak in winter then decrease as the breeding season approaches in March. It appears all crows join in winter roosts, even territorial breeding crows. Most theories suggest crows roost because it provides protection from predators and they dont mind congregating in large numbers as some birds do. When do crows mate? Early spring (March) is when crows usually court and mate. After mating, females build a nest in 5 to 13 days against the trunk of a tree at heights ranging from 6 to 60 feet above the ground.
