Double-crested Cormorant - NYS Dept. of Environmental Conservation

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Double-crested Cormorant

Phalacrocorax auritus

New York Status: Not listed

Federal Status: Not listed

Description

Double-crested cormorants nesting in a tree.
Double-crested cormorants nesting in a tree.
Photo by Marcelo J. del Puerto.

The double-crested cormorant is a medium to large seabird, with a body length of approximately 30 inches and a wingspan of 45 inches. From far away, adult birds appear mostly black, but a close-up look reveals several colorful details, including a yellow-orange "throat" patch, a blue gullet, and striking green emerald-like eyes. The species' common name refers to the paired whitish tufts of feathers on its head, named "nuptial crests", and are visible only on adult males during the start of the breeding season. Its long and powerful bill, about the same size as its head, ends in a sharply-hooked beak.

Even from a distance, the species can be readily identified by several behaviors and postures. Heavy-boned, it floats lower in the water than most other water birds. They are fast and strong fliers, often seen flying low, just above the water. In larger flocks, they will form a characteristic "V" pattern. Perhaps the bird's most characteristic posture is standing on a buoy, tree, rock, or dock with its wings spread out to dry. Unlike ducks and other waterfowl, the cormorant's feathers are partially water permeable and need to dry after being in the water. The bird's streamlined body, strong legs, webbed feet, and neutral buoyancy (does not sink or float) make it a very capable diver. Combined with good underwater vision and a strong beak, the cormorant is a great fish predator. In fact, several Asian cultures have traditionally used trained cormorants for fishing.

Life History

Cormorants cooling off by fluttering their gular sacs
Cormorants cooling off by fluttering their
gular sacs (featherless skin on the throat).
Photo by Marcelo J. del Puerto.

Double-crested cormorants start breeding between two and five years of age, depending on food availability. Marine birds nest primarily on the ground since few trees are available. However, inland populations use trees and build nests. Both marine and inland populations form colonies ranging from a few birds to thousands. They will readily nest with other species, particularly herons. After courtship and mating, the female lays up to seven pale blue or green eggs, though three or four is typical. Parents take turns incubating, with eggs hatching in about a month. The young are altricial, meaning they cannot fend for themselves, and fledge (leave the nest) after 35 days, depending on their level of nutrition. Older chicks form "crèches" or groups of young birds that receive communal care from adults.

Annual survival of adults is around 65%, but can be as high as 80%. The typical lifespan for a cormorant is over 8 years in the wild, though one banded bird reached 22 years and 6 months.

Distribution and Habitat

Breeding Bird Atlas data for cormorant distribution, 1980 to 1985Breeding Bird Atlas data for cormorant distribution, 2000 to 2005
Breeding Bird Atlas data for cormorant distribution,
1980 and 2000.

Double-crested cormorants are a common sight along our marine coastal areas and along the shores and islands of the Hudson River, Lake Ontario, St. Lawrence River, Lake Champlain, Oneida Lake, and other larger inland waterbodies. Beginning in October and November, double-crested cormorants leave New York state and migrate to southern states and the Caribbean and return in late March or early April after the inland waterways are free of ice.

Population and Management

Once affected by the insecticide DDT, cormorant populations in New York have exploded over the past 4 decades. The number of breeding pairs increased from 2,100 in 1985 to 10,500 in 2003 and rose further through the 2000s. The species has done so well, in fact, that it is displacing other seabirds from their nesting grounds, including herons and common terns. Cormorants often return to the same breeding grounds every year. Over time the accumulated guano (excrement) can kill trees and other vegetation, making it unsuitable for nesting.

New York is one of several states that manage double-crested cormorant populations. In addition, cormorant populations have also been controlled in the Canadian provinces of Quebec and Ontario. Population control has included hazing, oiling of eggs, and killing birds. The population is now believed to be leveling off because of control measures. Cormorants have occupied most of the available breeding sites, which also limits their expansion.

References:


Double-crested cormorant range map from The Birds of
North America
, maintained by the Cornell Lab of Ornithology.
  • Peterson, Roger T., 2002. Birds of Eastern and Central North America, Fifth Edition, Houghton Mifflin Harcourt, Boston, MA.

  • Sibley, D., Elphick, C., Dunning, J. B., & National Audubon Society, 2001. The Sibley Guide to Bird Life and Behavior. Alfred A. Knopf, New York.

  • Baicich, Paul J. and Colin J. O. Harrison, 1997. A Guide to the Nests, Eggs, and Nestlings of North American Birds, Second Edition. Academic Press, San Diego, CA.

  • Coleman, Jeremy T. H. 2008. Double-crested cormorant, Phalacrocorax auritus. Pages 152-153 in McGowan, K. J. and K. Corwin, Eds. The Second Atlas of Breeding Birds in New York State. Cornell Univ. Press, Ithaca, NY.

  • USGS Patuxent Wildlife Research Center. 2011. Longevity Records of North American Birds.

  • The Cornell Lab of Ornithology Birds of North America Online (leaves DEC website).

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