Courtesy Kenn Kaufman
Growing in numbers throughout its range, the Double-crested Cormorant is widely distributed across North America. It breeds locally along all coasts and extensively in Florida, the center of continent, and along the Great Lakes and the St. Lawrence Seaway, as well as in Mexico, Belize, the Bahamas, and Cuba. Most cormorants winter along the Pacific Coast from Alaska to Mexico, along the Atlantic and Gulf coasts from North Carolina to Belize, and inland on ice-free areas along large rivers and lakes.
A legend for the range map to the right can be found here.
Double-crested Cormorants are very adaptable; they may be found in diverse aquatic habitats, ranging from rocky northern coasts to mangrove swamps, lagoons, estuaries, rivers, small inland ponds, and large reservoirs. They are even more widespread in winter. These cormorants nest in trees near water, on cliffs, or on island beaches.
The diet of the Double-crested Cormorant consists predominantly of a wide variety of fish. Other aquatic animals are eaten as well, including crabs, shrimp, crayfish, insects, frogs, and salamanders. The cormorant dives from the surface and chases fish underwater, propelled by its powerful webbed feet. The bird then grabs the fish with its bill, rather than spearing it; upon surfacing, it flips the fish into the air, then catches and swallows it head-first.
Double-crested Cormorants first breed at 3 years of age. They nest in colonies, sometimes with other wading birds. The birds make a bulky nest of sticks and other bulky items, including seaweed and flotsam, often lined with grass in a tree near water, on a cliff ledge, or on a beach. The species frequently nests on human-made structures, such as bridges, channel markers, rock jetties, and pile dikes. They frequently pick up debris, including rope, deflated balloons, and fish nets, to incorporate into the nest. Accumulated fecal matter below nests sometimes kills the nest trees. When this happens, the cormorants may move to a new area or they may simply shift to nesting on the ground. The cormorants usually lay 3 to 4 pale blue eggs. Cormorant hatchlings are naked and helpless. Both parents care for the chicks. Double-crested Cormorant adults shade the chicks and bring them water, pouring it into the chicks’ mouths from their own. In ground-nesting colonies, young cormorants leave their nests and congregate with other youngsters, called crèches, returning to their own nests only to be fed. The young birds begin to fly at about 5 weeks, and become independent at about 9 weeks of age.
Some populations on the Pacific coast and in Florida are permanent residents, but most are migratory. They migrate by day in flocks, often forming “V”-shaped formations as they follow rivers or coastlines, headed from the coldest parts of their breeding range toward ice-free areas.