The family Phalacrocoracidae includes 6 species found in North America.
Cormorants and Shags occur in tropical and temperate regions, mainly on seacoasts or islands. Some species are found inland on lakes and rivers. They are medium to large-sized (50-100 cm long, 700-3500 gms) aquatic birds with a long neck, long wedge-shaped tail, short legs and large webbed feet. The bill is of medium length with a hooked tip.
Cormorants and shags feed mainly on fish caught under water by surface-diving and pursuit. The dive begins with a forward leap and the feet are used for underwater swimming. They also take crustaceans and cephalopods. The prey is captured in the bill and brought to the surface before being swallowed. Cormorants usually fish singly, but flocks may gather when prey is abundant. They sometimes cooperate by forming a moving line abreast, diving as they proceed.
They nest in colonies on rocky islands, cliffs or in trees, often with other species. Nests may be scrapes or heaps of vegetation on the ground or composed of sticks and other items if in trees. The male selects the nest site and brings the material to the female who builds the nest. Clutch size is usually 3-4, pale blue or green, usually unmarked with a chalky surface. Eggs are incubated by both sexes on the feet for 4 weeks. The chicks are naked at hatching but by 1 week of age are covered with black, gray and/or white down. Small nestlings take water from the mandible of the parents. When larger they are fed on regurgitated food taken from the throats of the parents. Young leave the nest at 4 weeks of age and fledge at 48-53 days. They are fed for 2-3 months after fledging. Age at first breeding is 2-3 years.
Cormorants - Patuxent Bird ID Center