Northwestern crow

The northwestern crow (Corvus brachyrhynchos caurinus) is an all-black passerine bird of the crow genus native to the northwest of North America. It is a subspecies of the American crow (Corvus brachyrhynchos), but it averages slightly smaller (33–41 cm in length) than the nominate subspecies with proportionately smaller feet and a slightly more slender bill. This taxon is perhaps impossible to identify in the field, and is largely identified by range, though even that method is contested.

Northwestern crow
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Corvidae
Genus: Corvus
Species:
C. brachyrhynchos
Subspecies:
C. b. caurinus
Trinomial name
Corvus brachyrhynchos caurinus
Baird, 1858
Northwestern crow range

Taxonomy

This subspecies was described by Spencer Fullerton Baird in 1858.[2] The American Ornithologists' Union considers it closely related to the American crow and it may be conspecific.[2] Hybrids with American crows had been reported, but not confirmed.[3]

In June 2020, following a recent study on the genetics of both the American crow and the northwestern crow, the American Ornithological Society's North American Classification Committee concluded that the two species are actually one and the same, thereby merging this species into a variation of the American crow.[4]

“Northwestern Crows were originally described based on size, being smaller than the American Crow, and behavior, but over the years the people who’ve looked at specimens or observed birds in the field have mostly come to the conclusion that the differences are inconsistent. Now the genomic data have indicated that this is really variation within a species, rather than two distinct species.”[5] - Terry Chesser, chair of the United States Geological Survey

Description

This subspecies' plumage is virtually identical to that of the American crow.[6] Individuals may be distinguished by in-hand criteria such as smaller wing chord and tail length, shorter tarsus, and smaller bill.[3] Identification percentages increase when sex of animal is known.[3] Like the American crow, the sexes look the same.[3] Older birds in breeding condition may be reliably sexed by in-hand criteria such as cloacal protuberance (male) or by brood patch (female).[3] Younger birds may not attain breeding condition as they assist at the nest.[3]

Distribution and habitat

This subspecies occurs in coastal regions and offshore islands of southern Alaska, south through British Columbia to Washington. Beaches and shorelines are the principal forage areas. It can often be seen in and around urban areas.

Behaviour

Diet

Very similar to that of the fish crow; the northwestern crow eats stranded fish, shellfish, crabs and mussels, and also searches through refuse containers for suitable food items. It has been seen to fly into the air with mussels and drop them onto hard surfaces to break them open. It also regularly eats insects, other invertebrates, and various fruits (especially berries). It raids other birds' nests to eat eggs and hatchlings.

Predators

An incomplete list includes cats, raccoons, raptors and ravens. The crows often gather in large groups to mob these predators.

Nesting

Generally solitary, but sometimes built in association with a few other individuals in small, loose colonies in trees or sometimes large bushes. Very rarely, it will nest on cliffs in a recess or even on the ground in a remote area if overhung by a rock for shelter. It is a typical crow nest with 4-5 eggs usually laid.

Voice

The voice is very varied, and many types of call are made, but the most common are usually described as a high pitched "caw" and the sound of a cork coming out of a bottle. A "wok-wok-wok" is given by a bird in flight if straggling behind the group, and various clicks and mechanical sounding rattles are also heard.

  • A pair of Northwestern crows in Seattle, Washington after foraging.
  • Advisory sign during nesting season of Northwestern Crow, Sidney, British Columbia
  • Colwood BC
  • Vancouver, BC
  • Homer, Alaska
  • Seward, Alaska
  • Northwestern crow fledgling
  • Steveston, BC

References
  1. BirdLife International (2012). "Corvus caurinus". IUCN Red List of Threatened Species. 2012. Retrieved 26 November 2013.CS1 maint: ref=harv (link)
  2. American Ornithologists' Union. (1983) Check-list of North American Birds. 7th Edition.
  3. Pyle, Peter. (1997). Identification Guide to North American Birds
  4. Chesser, R. Terry; Billerman, Shawn M.; Burns, Kevin J.; Cicero, Carla; Dunn, Jon L.; Kratter, Andrew W.; Lovette, Irby J.; Mason, Nicholas A.; Rasmussen, Pamela C.; Remsen, J. V.; Stotz, Douglas F. (2020-07-24). "Sixty-first Supplement to the American Ornithological Society's Check-list of North American Birds". The Auk. 137 (3). doi:10.1093/auk/ukaa030. ISSN 0004-8038.
  5. "Goodbye Northwestern Crow, Hello Mexican Duck". American Ornithological Society. 2020-06-30. Retrieved 2020-09-08.
  6. National Geographic Society. 1983. Field Guide to the birds of North America.

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