DISTINGUISHING FEATURES AND BEHAVIORS

Double-crested cormorants are long-necked black birds often seen sitting on piers and rocks in an upright position with wings open in a "spread eagle" posture. The yellow orange, unfeathered throat pouch of the double-crested cormorant distinguishes it from similar species. Adult birds in breeding plumage have a crest on either side of the head. Immature birds are dull brown to whitish on the chin, throat, and foreneck. In flight, the tail and head appear long, the neck crooked, and they often fly low near the water's surface. A traveling flock may form a line or wedge shape, but they fly silently, unlike noisy flocks of geese.

Cormorants feed on fish and aquatic invertebrates. They dive underwater and swim after fish using their strong paddlelike feet. The end of their bill is hooked to enable them to grasp onto fish.

The outer layer of feathers on cormorants are not waterproof, and when wet they add weight to the bird, making it easier to dive. The inner layer stays dry to provide insulation. After diving, cormorants stand on rocks or pilings and spread their wings to dry the soaked flight feathers.

Their eyes are adapted for both aerial and underwater vision. With a soft eye lens and strong eye muscles, they are able to change the shape of the lens to a more rounded shape to focus at shorter distances underwater.

Double-crested cormorants nest in colonies on islands in Narragansett Bay. Nests are built in live or dead trees, or on the ground, and are made of sticks, seaweed and debris.

RELATIONSHIP TO PEOPLE

Double-crested cormorants have only recently become common in Rhode Island. Before 1981, there were no nesting birds in our state, and they were only sighted migrating to their southern wintering grounds. Since 1981, year-round cormorant populations have been on the rise. The nesting population increased rapidly from 1,768 nests in 1992, to 2,087 in 1994. This non-native bird is competing for and destroying nesting sites of native wading birds that nest in live trees. When the cormorants nest in trees on isolated coastal islands, their droppings (guano) destroy the leaves and eventually kill off the trees in the nesting colonies. Some small islands on Narragansett Bay have been almost completely defoliated by cormorant droppings.