Because of their black colouration, cormorants are often referred to as sea crows. In fact, the family name, Phalacrocoracidae, means bald raven in Greek. While cormorants do appear black, close inspection reveals that they are, in fact, a variety of dark colours ranging from green and violet to ultramarine and bronze. In breeding plumage, these large seabirds have intensely bright patches, which occur in a variety of specific colours, around their eyes and throat. Cormorants possess a gular sac, or throat pouch, that has a variety functions. It acts as a holding area for larger prey, helps the bird rid itself of extra heat while panting, and in the breeding season, the bright colours of the pouch are used for display during courtship. Ranging from 63 to 101 cm in length, these water birds have distinctive long, slender, hooked bills. Found in both fresh and salt water, their diet consists mostly of fish, but small amphibians and crustaceans are also consumed.
Although their large feet make these birds exceptional swimmers, they are not elegant walkers. Often, the feet overlap and their clumsiness has led to many broken eggs! The structural characteristics that make cormorants such excellent swimmers, also affects their flying ability. The massive thigh and hip muscles that gives them strong underwater propulsion make them heavy in relation to the surface area of their wings. It is these characteristics that keep these large birds close to their roosts; they do not venture too far out to sea.