To view other waterbird trend pages, click a link below:
Shorebird trends
Diving Duck trends
Dabbling Duck trends
Grebe trends
Heron & Egret trends
Tern trends
Other waterbird trends
About Graphs
References
Double-crested Cormorant
Phalacrocorax auritus
Description
The Double-crested Cormorant, the most widespread and common of the North American cormorants, is a large, black cormorant with a long neck and yellow-orange throat. These cormorants only have the “double-crests,” or short black plumes on their head, during the breeding season.
Range
Double-crested Cormorants are found in summer along both the east and west coast of North America, and through the southern states and eastern Mexico. Cormorants are found year round in the Bay Area and the northwest coast of the US, as well as in Alaska, Baja California, Florida, and Cuba.
Diet
Cormorants dive for a variety of fish.
Natural History Notes
Double-crested Cormorants have specially adapted eyes to see while diving under water. Although avid divers and swimmers, these water birds are rarely seen out of sight of land. Double-crested Cormorants swim low in the water, often with just their heads and narrow necks visible. Out of the water, Double-crested Cormorants frequently spread open both wings, presumably to dry feathers. As the numbers of Double-crested Cormorants increase along the coast and inland, the bird is being blamed for decimating fish farms and declines in sport fishing.
In Point Reyes, the Double-crested Cormorant is common year-round, as a summer and winter resident and fall transient. Numbers of cormorants peak during the fall, from August to December, after large numbers of juveniles leave the Farallon Islands. In the late 1980s, the bird was discovered nesting on the Richmond-San Rafael Bridge and the Bay Bridge (Shuford et al. 1989).
Bolinas Lagoon Population Trends
The number of wintering Double-crested Cormorants on the Bolinas Lagoon is currently increasing. The population peaked at about 50 birds in 1979, then dropped to about 30 birds in 1992. Since 1992, the population has increased to about 48 Double-crested Cormorants.
