Phalacrocorax auritus auritus (Lesson)
Description.—Four toes all webbed together; bill long and strongly hooked at tip; tail stiff and moderately long; plumage thick and firm. 16Adults in breeding plumage: Glossy greenish black, save on back which is dark gray, each feather being margined with lighter gray; two filamentous tufts of black feathers on back of head; neck with thin sprinkling of silken white feathers during period of courtship; bill blackish, marked at base with dull yellow; sack under bill yellow; eyes bright green. Immature and adult in winter (the plumage usually seen in Pennsylvania): Without crests, and whole plumage brownish black, somewhat mottled beneath, and with light area on throat; eyes grayish green, not bright green. Length: About 30 inches.
Range in Pennsylvania.—A migrant found principally along the larger water-ways from about March 20 to May 10 and from September 15 to November 15. It is occasionally seen in winter when the water is free of ice.