Crows and ravens
Known to most as the "crow," the American crow (Corvus brachyrhynchos) has iridescent black feathers, a black beak curved down at the point, and black legs and feet. The northeastern region of the U.S. has the largest crow subspecies, the eastern crow, approximately 20 inches in length with a nearly 3-foot wingspan. Western and southern variations are smaller.
Crows make loud "cawww" sounds that vary to communicate several messages including feeding, grouping together and danger. While humans are the greatest threat to crows, large owls and hawks can prey on them. Crows like to nest in tall trees in early spring in our area, building nests of twigs and bark lined with leaves and grasses. They lay a clutch of about a half dozen 1 1/2-inch eggs, blue-green to olive in color with brown specks; these hatch at 18 days.Crows mate for life and are one of the few bird species in which the male helps defend the nest and feed the nesting female and fledglings. Crows are also intelligent and social, living in small groups. Crows will take turns feeding, with some watching for danger while others in the group feed. Crows are well-known to distinguish between a human carrying a weapon and a human that is not a threat. They eat almost anything, from grains and fruits to small rodents, birds, eggs and roadkill. In winter, they can be seen scratching through the snow for edible nuts, seeds or insects. Scarecrows have been used to help prevent these birds from damaging crops, although some research shows that crows may balance crop damage by feeding on insects attracted to field crops. Crows have been observed distracting other animals through group behavior to steal food. They have also been observed with primitive tool use, for example, using a stick to dig out insects.
The American crow is susceptible to the West Nile virus, typically dying within a week after contracting the virus. Crows are not known to transmit the virus to humans. However, the crow population in the U.S. is estimated to have decreased by nearly 50 percent in the last decade due to the virus. In the wild, the life span of a crow is typically seven or eight years, sometimes 15 years or more. Due to the existence of a large population of crows in Maryland, hunting is allowed in accordance with Department of Natural Resources regulations from late summer through late winter.
Seen also in our area and closely related to the American crow is the fish crow, slightly smaller than the American crow, with minor variations that include more slender bills and feet. However, the different call of the fish crow is the best identifier. Its call sounds more like a "wah-wah" or "nya-nya" that is different from the most common "caw-caw" of the American crow; to some it may sound something like a duck. The range of the fish crow is mainly along the eastern seaboard. While its preferred diet is aquatic life including fish, crayfish and shellfish, it also eats an omnivorous diet similar to the American crow. The fish crow, like its American crow cousin, is also highly susceptible to the West Nile virus.
Ravens differ from crows in both appearance and behavior. They are larger than crows, do not group together like crows and have a more rounded tail. This bird is more common in Western states than in the East; however, they are in the Appalachians as far south as Georgia.
Article by FCFCDB
Nature Notes for 3/17/2013