 The Nature of Cedar Mill
American Crow
By Kyle Spinks, Natural Resources Technician, Tualatin Hills Park and Recreation District
[Ed. Note: The crows seemed particularly noisy and obtrusive early this spring in my neighborhood. Then I realized that their big nest, which I’d seen once or twice, had been in the trees down the way that have since been removed to make way for houses. They were having meetings to discuss the situation, one day in the oak tree, the next in the cottonwood. I think I counted 30 birds one morning. So I asked Kyle to give us a little more information about these noisy, sociable and ubiquitous birds.]
Probably one of the first few birds any child from our area learns is the American crow (Corvus brachyrhynchos). The “caw, caw, caw” heard high up in the trees make this distinctive, iridescent black bird one of the easiest for anyone to identify, even from a great distance. Here in the northwest, we can see crows regularly in our neighborhoods, parks, and open spaces, and they often will roost in large numbers during winter or when feeding communally. This gregarious, highly intelligent bird has become a common urban resident, though its range extends throughout North America in almost all habitats, and it overlaps that of its close cousin, the Common Raven, which typically occupies habitats at higher altitudes.
Native Americans of the Pacific Northwest considered the crow a mischievous animal or even a bringer of doom. In urban settings, the same feelings may be elicited when we have to chase the crows from a garbage can or we see them feeding on carrion alongside the road. And some people aren’t all too happy to be awakened by the dawn cacophony of a bunch of crows in the trees just outside our homes.
However, crows occupy a valuable niche in the wilds, spreading seeds from the many berries they eat throughout the forests. The carrion they eat gets ‘reprocessed’ and deposited back into the natural areas as ready-to-use fertilizer that our native plants need. Of special note is the documented use of tools by crows and ravens to gather food, including using pieces of bent grass to collect insects.
Crows will often roost in large groups; in some cases up to several thousand crows may take up overnight residence in a grove of trees. This communal behavior provides a measure of defense against bird predators, such as hawks or falcons, as well as re-enforcing familial and colony ties.
Crows mate from February to about June and 3-4 eggs are laid in a shallow, bowl-shaped nest of sticks and twigs lined with softer fibers. The eggs hatch in about 18 days and the young begin to fly (fledge) in about 35 days. Both parents feed the young, and will defend the helpless young until they fledge. It is common for second- and third-year fledglings to help with the defense of the territory of the parents. This behavior, called cooperative breeding, is unusual among bird species, but is just another example of the why the American crow is so distinctive.
Crows are susceptible to West Nile Virus, which they get from mosquito bites. However, only two crows have been found infected in Washington County since 2006. “Some bird species such as crows, ravens, and jays are especially susceptible to West Nile virus. Although there is no evidence that a person can get the virus from picking up a dead bird, we recommend avoiding handling dead birds with bare hands,” says Toby Harris, Public Health Program Supervisor for Washington County’s Department of Health and Human Services.
|
