The Pelagic Cormorant, the smallest and most widely distributed of six cormorant species inhabiting the North Pacific, ranges from the Arctic waters of the Chukchi and Bering seas south through temperate waters along the North American Pacific Coast to Baja California and along the Asian coast to southern China. It is among the least gregarious or social of the cormorants, nesting on steep cliffs along rocky and exposed shorelines, either in loose colonies or far from nearest neighbors.
Although the Pelagic Cormorant is exclusively marine in habits, its name is misleading, since it prefers inshore areas. This species is a component of littoral communities and feeds primarily on solitary fish and invertebrates on the bottom. These and other aspects of its morphology and behavior qualify it as a member of the shag subfamily Leucocarboninae, according to Siegel-Causey ( Siegel-Causey 1988b ).
The North American population totals about 130,000 birds, the majority of which occur in Alaska. Local populations often fluctuate considerably because of movement among breeding sites. During breeding, Pelagic Cormorants show a rich repertoire of behavioral displays. The species is also conspicuous on diurnal roosts, where it may spend considerable time drying its plumage. Like all other cormorants, it is sensitive to disturbance at colonies and vulnerable to oil spills, gill-net entanglement, and contamination of marine food webs.
In part because of its more solitary habits, this species is still relatively poorly studied compared to other Pelecaniformes. However, important long-term population and dietary studies have been conducted at the Farallon Is., CA ( Ainley and Boekelheide 1990 ), and breeding behavior and diet has been studied at Mandarte I., British Columbia ( Van Tets 1959 , Robertson 1974 , Siegel-Causey and Hunt 1986 ; see also Cannon 1990 ). Other investigations have focused on the dynamic nature of colony-site selection and attendance ( Carter et al. 1984 ) and the use of diurnal roost sites (Hobson and Sealy Hobson and Sealy 1985a , Hobson and Sealy 1986 ).