Systematics

Phalacrocorax is from the Greek “bald-headed raven”; auritus is Latin for “eared,” referring to the crests above the eyes.

Considerable variation in body size and in the color and size of crest. Alaskan birds are largest, with long, straight crests that are mostly white; individuals from eastern populations are smaller, with short, all-dark, curled crests. Smallest individuals are from the Bahamas. Distribution of crest characters is poorly known, in part because crests are present only briefly, early in breeding season. Colors of skin on face and throat also vary seasonally and deserve attention (see Appearance, below).

Five subspecies are recognized by Dorst and Mougin (1979) and Watson et al. (1991); differentiated by size (see Measurements, below) and crest characters:

P. a. auritus (Lesson, 1831): Breeds over most of range in e. and central North America except the Southeast; largely migratory, wintering from mid-Atlantic Coast to Gulf of Mexico; moderately large; crests black, curled (see Fig. 2).

P. a. cincinatus (Brandt, 1837): Breeds in Alaska, winters south to British Columbia; largest; crests mostly white, straight.

P. a. albociliatus Ridgway, 1884: Breeds along Pacific Coast from British Columbia to Baja California and inland, possibly to New Mexico, Utah, and Montana; ranges south to Sinaloa, Mexico; white in crest variable.

P. a. floridanus (Audubon, 1835): Resident in Florida and Caribbean; small and dark.

P. a. heuretus Watson, Olson, and Miller, 1991: Resident on San Salvador I., and possibly other islands of Bahamas (Watson et al. 1991) and Cuba (Garrido and Kirkconnell 1992); smallest and darkest; crests not described.

Characteristics of those breeding in Mexico have not been described. No detailed studies of differences or of genetic variation among subspecies have been published. Extent of introgression unknown, and studies from regions of overlap have not examined whether assortative mating occurs. Banding recoveries suggest that little mixing occurs across Rocky Mtns. (Dolbeer 1991).

Double-crested Cormorant is thought to be closely related to Neotropic Cormorant, and the two are treated as allospecies by some authorities (see Sibley and Monroe 1990). Coexistence of small form (heuretus) with Neotropic Cormorant in Bahamas bears study. Phylogenetic analysis of osteological characters by Siegel-Causey (1988) placed Double-crested Cormorant with Neotropic Cormorant and 3 species from Australia and India in genus Hypoleucos within subfamily Phalacrocoracinae, which also includes Great and Brandt’s Cormorant. This arrangement is not followed by Am. Ornithol. Union (1998). Some recent classifications divide the family into 2 genera rather than 2 subfamilies.