Crows as a group are somewhat territorial. Some groups are highly aggressive and don’t leave their area in search of food. They have fixed borders that they defend against other crow clans. Intruders are attacked and driven off by the owners.

The British term for a flock of crows is a “murder” of crows. If crows find a great horned owl during the day they will mob it, sometimes for hours. At night the owl rules and may take over a crow’s nest as its own. The crow, realizing its disadvantage, will not argue the point and will leave rather than be killed by the owl.

In some instances in fall and...