A variety of facts about crows
March 8, 2023
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 winter, American crows search for food over very large areas. My Christmas bird count area covers Whidbey Island, which supports flocks up to 1,000 birds, and goes from Anacortes south to Coupeville, with larger flocks headed north in the evening. They spend each night roosting in the Douglas Fir covered island just south of Washington Point. The island is about half a mile offshore and is not good habitat for rabbits or other small mammals. Great horned owls do not go there because of lack of prey. A canopy of evergreen trees keeps the wind and rain at a minimum. This large island provides shelter for a large flock of crows.
American crows are sometimes found in winter with northwestern crows in large mixed flocks. This is where separating the two species becomes more difficult. Both have a very similar profile, with the northwestern crow being slightly smaller. It also has a more delicate bill and its feet are smaller.
The call is quite similar, through the two species do not interbreed. DNA testing confirmed they are distinct.
Northwestern crows breeds along the Pacific coast closer to saltwater. Their territory goes north to Alaska where the American crow is not found. Crows nest in communal areas, sometimes close together as a clan. They are very tame when in close association with humans. During nesting season crows do organized searches for birds’ nests, taking both eggs and young. They methodically search each tree limb, sometimes daily.
Crows are very smart animals and have very good memories. There are northwestern crows nesting in Seattle within the city limits. Researchers from the ornithology department of the University of Washington ran a crow banding operation in Seattle and used Halloween masks to disguise themselves and prevent the nestlings from recognizing them. A Ronald Reagan mask was worn during the bandings and became well known. Some months later a crow was recaptured and it recognized the mask. It became upset and made alarm calls above the intruder it recognized as the researcher who had walked down the street with the mask on. The crow followed the masked bander out of the area, complaining loudly.