Phalacrocorax auritus

Phalacrocorax auritus - Double-Crested Cormorant

Habitat Double-crested Cormorants are the most widespread cormorant in North America, and the one most frequently seen in freshwater. They breed on the coast as well as on large inland lakes. They form colonies of stick nests built high in trees on islands or in patches of flooded timber.

Range Year-round, double-crested cormorants are found in Florida and the Aleutian Islands, off of Alaska. During their breeding season (summer), double-crested cormorants are found throughout the Great Plains of the United States and into the provinces of Canada (Alberta, Saskatchewan and Manitoba). In the winter, they are found in the Deep South of the United States and the Outer Banks of North Carolina.

Description Cormorants are large birds (70 to 90 cm in length, 1.2 to 2.5 kg) with dark brown or black plumage that has a dull greenish or bronze sheen. They have lean bodies, long necks and relatively short wings. They have long beaks with a hooked upper mandible and bright orange-yellow skin that covers the face, throat and base of the bill. Their black feet are webbed feet and found on short legs, and their tails are wedge-shaped. During the breeding season, double-crested cormorants have two curly black crests on their heads, blue eyelids, a dusky bill and orange on the throat sac and lores. In the winter, adults lack the crests, show no blue on eyelids, have a yellow bill with red on gular sac, and yellow behind the ocher. Males are slightly bigger than females. Juveniles are much duller in color than adults. They are usually dark brown with grayish or whitish coloring underneath. The crests are white in cormorants from Alaska, and black in other regions.

Ecological Notes The double-crested cormorant's diet is almost all fish, with just a few insects, crustaceans, or amphibians. They eat a wide variety of fish (more than 250 species have been reported), and they have impressive fishing technique: diving and chasing fish underwater with powerful propulsion from webbed feet. The tip of a cormorant’s upper bill is shaped like a hook, which is helpful for catching prey. Double-crested cormorant's have 1-2 broods a year, with 1-7 eggs per clutch. Nests can be on the ground, on rocks or reefs with no vegetation, or atop trees.

Personal Information The double-crested cormorant was frequently flying above freshwater in formation while we were driving. We saw this bird the most on the first day of the trip, while visiting the Oregon Inlet.

References All About Birds Animal Diversity Web, University of Michigan

Additional Information

Carter, M.C., Bishop, J.D., Evans, N.J.,Wood, C.A. 2010. Environmental influences on the formation and germination of hibernacula in the brackish-water bryozoan Victorella pavida Saville Kent, 1870 (Ctenostomata: Victorellidae). Journal of Experimental Marine Biology and Ecology, 383(2):89-95.

This paper studied a different species of Bryzoan and the environmental factors which impacted the development of this organism. The authors specifically studied water temperature, salinity, and how these influenced germination.

Carter, M.C., Gordon, D.P., Gardner, J.P. 2009. Polymorphism and variation in modular animals: morphometric and density analyses of bryozoan avicularia. Marine Ecology Progress Series. 399:117-130.

The authors of this paper focused upon the genus cheilostome and the unique characteristics present in this group. The individual avicularia have the unique characteristic of being polymorphic. As a result the authors studied numerous sample to better understand the morphological differences in each specimen.

Contributed by Cassie Nix - 2014

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