The Northwestern Crow lives along the coastal strip of the northeast Pacific from Alaska to northwestern Washington. Clearing of forest along the coast and rivers has led to an expansion of its historic range, and its adaptable nature has made it a common feature of the urban landscape.
Very similar in appearance to the American Crow (Corvus brachyrhynchos), this species is smaller and has a lower-pitched voice. In areas of overlap, however, such as northwestern Washington, similarity between the species makes identification difficult. The 2 species are thought to constitute a superspecies. Many consider the Northwestern Crow a subspecies of the American Crow.
The Northwestern Crow nests in isolated pairs or in loose clusters in exclusive territories, often near intertidal flats, where it procures much of its food in communal flocks. Some pairs have an immature helper that assists in feeding and defending the nestlings. The omnivorous food habits of this species are an offshoot of its adaptable nature. It is just as adapted to digging clams and catching small crabs and fish on beaches as it is to snatching eggs from unwary seabirds, helping itself to unattended picnic baskets, and rummaging in garbage cans in urban areas. Ecologically it is a counterpart of the eastern U.S. Fish Crow (Corvus ossifragus).
The basic biology of the Northwestern Crow, despite the conspicuous presence of this species in coastal areas, was until recently largely unknown. What is known is based almost entirely on studies conducted on Mandarte Island (6.3 ha; 2 km from nearby land) and Mitlenatch Island (35.5 ha; 6.5 km from nearby land), in Georgia Strait, British Columbia, both of which are inhabited by nesting seabirds. The islands are partly bare, partly covered with short vegetation interspersed with coppices of shrubs and trees (Drent et al. 1964, Brooke et al. 1983). Breeding biology is based largely on Drent et al. 1964, James 1979a, Butler 1980, Butler et al. 1984, Richardson et al. 1985, Verbeek Verbeek 1991, Verbeek 1995, Campbell et al. 1997b, and much unpublished data (NAMV). The species is among the northernmost known to have helpers at the nest (Verbeek and Butler 1981). Northwestern Crows store food, particularly during low tide, and retrieve it later, mostly during the following high tide. This behavior has been studied in detail (James and Verbeek James and Verbeek 1983, James and Verbeek 1984, James and Verbeek 1985, Verbeek 1997). Aspects of foraging and energetics are available in Zach Zach 1978, Zach 1979, Richardson Richardson 1983, Richardson et al. 1985, James and Verbeek 1984, Richardson and Verbeek Richardson and Verbeek 1986, Richardson and Verbeek 1986, and Verbeek Verbeek 1982, Verbeek 1990 . Much remains to be learned about this species (see Priorities for future research, below).