Throughout most of the year, they flock in groups ranging from family units to several hundred birds. During winter, crows may gather by the tens of thousands in areas where food is plentiful. Later, these flocks break up as mate selection takes place. Males vie for mates through fighting and spectacular flight routines. Once paired, male and female search out a secluded woodlot to raise their brood.
Some naturalists believe crows mate for life.
A nest site is usually chosen away from those of other crows. Most often, nests are built in the crotch of a tree, 10-70 feet above ground, usually more than 25 feet. A typical crow's nest is a large, substantial basket, 22-26 inches across, built of twigs, sticks, bark and vines. The deep central cup is lined with moss, shredded bark, grass, deer hair, fur, feathers or similar material. May. Eggs are oval, bluish-green, and blotched and spotted with brown and gray.