Northwestern crow

From Wikipedia, the free encyclopedia

Northwestern crow
Corvus caurinus (profile).jpg

Least Concern (IUCN 3.1)[1]
Scientific classification e
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
Corvus caurinus map .jpg
Northwestern crow range

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 clinal variant or subspecies of the American crow (Corvus brachyrhynchos), but it averages slightly smaller (33–41 cm in length) than other subspecies. With the exception of calls, this taxon is almost impossible to identify in the field, and is largely identified by range.

Taxonomy[]

This taxon was described by Spencer Fullerton Baird in 1858.[2] The American Ornithologists' Union considers it a subspecies of the American crow.[3] It forms a hybrid swarm with American crow (sensu stricto) in coastal Washington and British Columbia.[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 American Ornithological Society North American Checklist Committee.

Description[]

This subspecies' plumage is virtually identical to that of the American crow (sensu stricto), but averages smaller in size.[6] Like the American crow (sensu stricto), the sexes look the same.[citation needed] Older birds in breeding condition may be reliably sexed by in-hand criteria such as cloacal protuberance (male) or by brood patch (female). Younger birds may not attain breeding condition as they assist at the nest.[citation needed]

Distribution and habitat[]

This subspecies occurs in coastal regions and offshore islands of southern Alaska, south through British Columbia to Washington.[4] Beaches and shorelines are the principal forage areas.[citation needed] 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.[citation needed] It has been seen to fly into the air with mussels and drop them onto hard surfaces to break them open.[citation needed] It also regularly eats insects, other invertebrates, and various fruits (especially berries).[citation needed] It raids other birds' nests to eat eggs and hatchlings.[citation needed]

Predators[]

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

Nesting[]

Generally solitary, but sometimes built in association with a few other individuals in small, loose colonies in trees or sometimes large bushes.[citation needed] 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.[citation needed] It is a typical crow nest with 4-5 eggs usually laid.[citation needed]

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.[citation needed] 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.[citation needed]

Gallery[]

  • 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.
  2. ^ American Ornithologists' Union. (1983) Check-list of North American Birds. 7th Edition.
  3. ^ 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): ukaa030. doi:10.1093/auk/ukaa030. ISSN 0004-8038.
  4. ^ Jump up to: a b Slager, David L.; Epperly, Kevin L.; Ha, Renee R.; Rohwer, Sievert; Wood, Chris; Hemert, Caroline; Klicka, John (2020). "Cryptic and extensive hybridization between ancient lineages of American crows". Molecular Ecology. 29 (5): 956–969. doi:10.1111/mec.15377. ISSN 0962-1083.
  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.

External links[]

Image links

Sound links

Video links

Retrieved from ""