For the past month or so, people in Denver’s Park Hill neighborhood have revisited scenes from Alfred Hitchcock’s “The Birds.”
Quiet mornings are shattered by a crescendo of cawing and screaming from hundreds of roosting crows. They wheel, climb, dive and fly in and out of a tree or two, like a scene straight out of Hitchcock’s thriller. But crows gathering in large roosting flocks is normal late-fall and winter behavior and is nothing to be alarmed over.
Appropriately for the phobic response it sometimes generates, a large gathering of crows is called a “murder.”
Kevin L. McGowan, a Cornell University biologist and an expert on crow behavior, says scientists aren’t sure why crows gather in these large flocks, though the leading hypotheses suggest that the roosts are near reliable food sources, that their numbers provide protection against predators and that the crows share information about good places to forage.
As spring approaches, these murders will break into family groups of two to eight birds, which then establish a home territory. Crows behave much like wolves, in that an alpha male and female head the family. Throughout spring and summer, these family groups focus on reproduction and rearing their nestlings and fledglings.
This year’s fledglings, who won’t be sexually mature for two years, might remain with the family group for a year or more before they move on to establish their own nesting sites. Older siblings often bring food to the nest and help guard it against predators, such as snakes, hawks, owls and other crows.
Crows themselves are predators, stealing eggs and nestlings of other birds, especially smaller songbirds. It is not uncommon to see a crow eating a nestling while its frantic parents fly around the big bird, screaming helplessly. But that’s nature.
So relax and rest easy, Denver neighbors. The Hitchcock- ian behavior you’re seeing is temporary, and no threat to you. But I, for one, am keeping an eye out for the nearest shelter. Just in case.
Denver naturalist Art Elser lives in Park Hill. He is the author of several nature guides, including one about raptors at the Plains Conservation Center and prairie wildflowers.
