Vancouver Avian Research Centre

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Species: Northwestern Crow Corvus caurinus

Description:

Northwestern Crows are among the most ubiquitous birds in the urban environment particularly along the western coast of North America from Alaska to Oregon.

They are readily identified from their entirely black plumage, gregarious habit and their high-pitched “caw” with which they sometimes call with impunity.

Northwestern Crow seems to form part of a species complex with the very similar American Crow, but it concentrates more in intertidal habitats. Urbanization from the early twentieth century onwards has been good for this species.

Identification:

General: Like most other Corvids, Northwestern Crows tend to be larger than other passerines with glossy black plumage. It possesses long legs and a sturdy bill. Adults weigh between 340 g to 440 g and measure between 33 cm to 41 cm in length.

Adult Male: Similar in plumage to the female but slightly larger in body size. Older individuals in breeding condition can be sexed in-hand for cloacal protuberance.

Adult Female: Similar in plumage to the male but slightly smaller in size. Older individuals in breeding condition will have a brood patch.

Juvenile: Birds less than 3 months would have looser and fluffier feathers of a dull black color and their eyes are blue instead of the brown-gray of adults. Those aged 3 to 15 months share with adults the black plumage but with less iridescence.

Similar Species: Very similar to the more inland American Crow (Corvus brachyrhynchus) but can be distinguished by its smaller feet and more slender bill. Its call is also more resonant. It is also smaller than the less social Raven (Corvus corax).

Behavior: Often seen in groups poetically termed a “murder of crows”. Flocks can be observed flying to their roosts as evening approaches. While foraging on the ground they will either hop or walk. Sometimes they follow people in the hopes of scoring on a tidbit.

Habitat: A common visitor to residential lawns and other urban habitats it is also at home in more naturalized areas. Its original habitat is along the shorelines and beaches.

Information:

BC is considered to support most of the global population of this species. Northwestern Crows like many Corvids demonstrate intelligent and opportunistic behavior. These traits have earned them both derision and admiration.

Its reputation as a nest predator and habit of bullying and preying on smaller birds and other vertebrates has given it the label of varmint among historical records. It has also been accused of tearing up the sod of lawns in its foraging for earthworms and grubs and raiding crops.

All social species like the Corvids develop a kind of intelligence that humans tend to identify. A demonstration of its social intelligence is the observation of mobbing behavior towards predators such as raptors.

It is not considered migratory but it will leave from exposed to more sheltered areas near human habitation during winter. It is a year-round resident in British Columbia.

They breed from March to July and typically nest in trees or shrubs along forest edges close to the ocean. The female incubates the eggs for about 18 days. At this stage the pair becomes protective and territorial and they can be bold enough to attack human passersby. A pair might even retain a helper from a previous brood that will assist in feeding and protection of its younger siblings. Not normally considered a colonial nester, groups of 2 – 19 pairs have been recorded in BC.

Past research has indicated a 57% success rate for nests to fledge at least one young which is usually about 31 days after hatching. Parents will still feed their young until they are at least 77 days old. A fledged bird can expect to live as long as 12 years in the wild.

Conservation Status: (Least Concern)

It has a fairly stable population in recent years, but it has shown a substantial increase compared to records from the early twentieth century. Where its range is sympatric with the American Crow, hybrids have been reported but not confirmed. Unique features of this crow could be lost through genetic swamping if the American Crow expands its range. Nevertheless, the Northwestern Crow’s catholic diet and cleverness has enabled it to be among the few species able to cope with anthropogenic disturbances to its natural habitat.
 

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