Double-crested Cormorant

Phalacrocorax auritus

(c) Glen Tepke
  • PHALACROCORACIDAE
  • Cormorants
  • Pelecaniformes
  • Cormorán Orejudo, Cormorán Bicrestado, Corúa de Mar
  • Cormoran à aigrettes
Introduction
The Double-crested Cormorant is the most numerous and widespread North American cormorant. This large, dark waterbird is the only cormorant that occurs in large numbers inland, near fresh water, as well as on the coast. Cormorants (from the Latin for "sea crow") are often seen floating low in the water, neck and bill raised, or perching upright near water to dry their outstretched wings.
(c) Shawn Carey
Appearance Description
Double-crested Cormorants weigh from 3.3 to 6.6 pounds (1,500 to 3,000 grams, depending on gender and subspecies), and measure 33 inches in length, with a wingspan of about four feet. Sexes look similar, with short, dark legs, a long black body and neck; a lighter colored bill with a hooked tip, bare orange skin around the face and chin. Breeding adults have brilliant turquoise eyes and mouth lining. A small curled plume on either side of the crown may be seen during the breeding season. The long neck is kinked in flight. Because their feathers are not waterproof, Double-crested Cormorants often spread their soaked wings out to dry after a dive. This incomplete waterproofing helps reduce buoyancy, a valuable attribute for a diving seabird.
Range Map
Courtesy Kenn Kaufman
Range Distribution
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.
Habitat
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.
Feeding
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.
Reproduction
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.
Migration
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.
CBC Graph
Graph Legend
Annual Population Indices
  • 1,650,000
  • 1,630,000
  • Increasing population; no current conservation concerns
Population Status Trends
Double-crested Cormorant populations decreased in the 19th and early 20th centuries due to human persecution at nesting colonies. Protective legislation led to population recovery in the 1920s, until the impacts of pesticide use in the 1950s and 1960s caused numbers to drop once again. The National Audubon Society listed the cormorant as a species of special concern in 1972, the same year DDT was banned. Since then, cormorant numbers and ranges have both been on the rise, particularly in eastern and central North America, as shown by BBS and CBC data.
 
An explanation of the Annual Population Indices graph displayed to the right can be found here.
Conservation Issues
Double-crested Cormorants have a long history of being persecuted by humans. Recent increases in their numbers have spurred renewed controversy. These increases have been most notable in the northern and eastern parts of the breeding range, and in southern states where these birds winter, causing conflicts with local catfish farms. Double-crested cormorants are perceived to be detrimental to such fish farms, as well as to sport fisheries.
 
In natural environments, fish species of direct interest to fishermen rarely make up a large part of the cormorants’ diet. However, cormorants feed opportunistically on readily available fish, often congregating where these fish are easily caught, such as after fish-stocking releases, downstream of fish hatcheries, or at aquaculture facilities. The extent of the economic impact is difficult to establish. The United States Fish and Wildlife Service recently extended cormorant control options to other government entities in the central and eastern U.S., although not to the public (i.e., there is no hunting season). To reduce cormorant impacts, both lethal and non-lethal programs (the latter include egg oiling, pyrotechnics, and improved aquaculture practices) have been carried out in various locations. Many government agencies in the U.S. and Canada are exploring how best to address this situation.
 
On East Sand Island in the Pacific Northwest, researchers are studying how social attraction techniques, such as decoys, audio playbacks of cormorant colony calls, and artificial stick nests) can help to restore or relocate Double-crested Cormorant colonies. Their studies have proven successful, with cormorants attempting to nest on eight of nine social attraction plots.
What You Can Do
Join beach cleanups in your area. Properly discarding of debris, particularly plastic, will prevent cormorants and other waterbirds from eating it.
 
Don’t discard used oil into city sewers or municipal water supplies. It can end up in the ocean where cormorant rest and feed.
 
Dispose of monofilament lines, hooks, and fishing lures properly; cormorants can become entangled in this gear.
 
Don’t disturb nesting cormorants when hiking or boating; prevent dogs and children from disturbing them. Cormorants are very sensitive to disturbance near the nest; when scared from their nests, gulls will frequently feed on their eggs and young.
 
Make environmentally-friendly seafood choices, which helps protect fish that cormorants and other waterbirds depend upon. Learn more at http://seafood.audubon.org or http://www.mbayaq.org/cr/seafoodwatch.asp
 
For actions you can take, including Audubon activities, please visit our resources page.
More Information
Learn about ocean conservation at http://www.livingoceans.org/index.shtml
 
Visit our resources page for more information about this species.
Natural History References
Hatch, J. J., and D. V. Weseloh. 1999. Double-crested Cormorant (Phalacrocorax auritus). In The Birds of North America, No. 441 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
 
Kaufman, Kenn. 1996. Lives of North American Birds. Houghton Mifflin Company, New York.
 
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, Inc., New York, 2000
Conservation Status References
Hatch, J. J., and D. V. Weseloh. 1999. Double-crested Cormorant (Phalacrocorax auritus). In The Birds of North America, No. 441 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
 
Kaufman, Kenn. 1996. Lives of North American Birds. Houghton Mifflin Company, New York.
 
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, Inc., New York, 2000