DOUBLE-CRESTED CORMORANTS AND 

FISHERIES IN THE GREAT LAKES BASIN

Fact Sheet

Introduction

Natural History

A Population Resurgence

Issues

Federal and State Responsibilities

Management Activities

What Comes Next?

For Further Information

Introduction

Flying low, in a straight line or ragged-V formation, large dark birds fly past, 

feathers rustling as they settle on the water. Swimming with bodies submerged, 

head and neck above water, bills pointed upward, they dive under water to catch 

fish. Taking flight, they head for another destination in the Great Lakes basin. Not 

to be confused with geese or loons, the birds are double-crested cormorants, 

called crow-ducks by European settlers, and Phalacrocorax auritus, by bird 

scientists.

Adult birds look alike, with dark plumage tinted a greenish gloss on the head, 

neck and underparts. They have slender, hooked bills, with webbed feet set well 

back on their body, orange facial skin, and an orange throat pouch, like their 

relative the pelican. The species is named for the two small tufts or crests of 

feathers, that appear for a short period of time on either side of the head of adult 

birds in breeding plumage. One to two year old juvenile cormorants have gray or 

tan plumage.

Natural History

Double-crested cormorants reside in many locations throughout North America. 

They nest along the Pacific coast from Southwest Alaska to Mexico, and from 

lakes in central Alberta to James Bay and Newfoundland, south along the Gulf of 

Mexico. Along the Pacific coast and the southern Atlantic coast, populations are 
resident year-round. The interior population, centered in the northern prairies, 

spread eastward and first nested on the Great Lakes in 1913. The birds in the 

Great Lakes population migrate south, along the Atlantic coast and Mississippi 

River drainage to overwinter in the southeastern states and Gulf of Mexico. By 

May, birds have returned north to breed and rear their young. They often nest on 

islands in the company of terns and gulls, great blue and black-crowned night 

herons, and great and snowy egrets. Nests are constructed from sticks and twigs 

and located in trees or on the ground. They usually contain from two to four light 

blue eggs. Both adult birds incubate the eggs for about 28 days by wrapping their 

feet around them, and care for their young until they become fully independent, 

about 10 weeks after hatching.

Cormorants are expert divers, adapted naturally to forage under water for fish. 

Fully-webbed feet propel slim, streamlined bodies on dives usually from 8 to 20 

feet. Greater depths are possible. Eye muscles are specialized to allow acute 

vision both above and under the water. Feathers absorb moisture, helping 

cormorants to stay under water for about 30 seconds. After foraging, cormorants 

often dry their feathers by perching in a distinctive wing-spreading posture.

The Great Lakes population of double-crested cormorants was devastated during 

the 1960s, primarily by the effects of chemical contamination especially DDT. 

Because they are fish-eating birds at the top of the food chain and long-lived (up 

to 20 years), adults accumulated pesticides and other toxins from the bodies of 

their prey. These chemicals caused reproductive failure, and chicks that hatched 

sometimes had crossed bills, club feet, and eye and skeletal deformities. In 

addition to contamination, human disturbance and nest destruction contributed to 

the decline.

In the early 1970s the Great Lakes population had plummeted, with few birds 

remaining or breeding successfully. In Wisconsin, the species was placed on the 

list of threatened and endangered wildlife. Nesting platforms were erected to aid 

their recovery. In 1972, double-crested cormorants were added to the list of 

species protected by the 1918 Migratory Bird Treaty Act. Despite these 

conservation efforts, the Great Lakes population continued to decline, with few 

breeding birds remaining or breeding successfully. The devastation of the Great 

Lakes cormorant population was a grim example of the declining health of the 

Great Lakes ecosystem.

A Population Resurgence

Today, the Great Lakes population of double-crested cormorants is at historic 

highs. Pollution control has lowered concentrations of toxic contaminants in their 

food supply, food is ample throughout their winter and summer ranges, and they 

are protected by federal and state laws. Nesting populations can be found on all 
the Great Lakes in both United States and Canadian waters, on inland lakes like 

Lake Champlain and Oneida Lake, and on the Niagara River.

Scientists do not expect the population to grow continuously. Instead, the number 

of birds should decline eventually, and then stabilize. Nesting habitat may 

become an important limiting factor. Disease may also play a role in this reversal. 

Although the cormorant population resurgence may indicate enhanced water 

quality in the Great Lakes, it has been accompanied by concern and controversy 

about the effects the birds may be having on stocks of recreational and 

commercial fish species, and island nesting habitat.

Issues

Because cormorants are conspicuous fish-eating birds, anglers in the Great 

Lakes basin may consider them a nuisance species and a threat to populations 

of recreational and commercial fish species. However, studies of the feeding 

habits of cormorants show the birds feed on many fish species, concentrating on 

the ones that are easiest to catch. Adult birds eat about one pound of fish per 

day. Because the ease with which a fish can be caught depends on such factors 

as distribution, relative abundance, and behavior, a cormorants’s diet can vary 

considerably from site to site and throughout the breeding and nesting seasons. 

All told, small (three to five inch) fish like alewife, yellow perch or gizzard shad 

provide most of their food. The birds find these fish in large schools, sometimes 

in shallow water.

Cormorants also feed on steelhead, lake and brown trout when available, 

especially when recently-stocked schools of small fish can be found in shallow 

near shore waters. Population level effects from cormorant predation on lake 

trout, salmon or steelhead are not apparent though, as diet studies indicate the 

birds consume very few of these fish in open waters. Can large colonies of 

cormorants reduce local populations of catchable-size pan fish like sunfish and 

rockbass, or sportfish like smallmouth bass, walleye pike, or yellow perch 

sufficiently to compete with anglers? Recreational and commercial anglers in 

some locations in the Great Lakes basin believe they can. Until biologists obtain 

additional information, the answer to this question remains unclear.

It is clear, though, that double-crested cormorants can feed heavily on small fish 

being raised commercially on minnow farms for bait, or for human consumption 

at fish farms or aquacultural sites. Also, in some locations within the Great Lakes 

basin, double-crested cormorants are competing with other colonial nesting water 

and wading birds for the same island nesting sites. A special concern exists 

when this competition jeopardizes the reproductive success of rare, threatened, 

or endangered plant and animal species.
Federal and State Responsibilities

The population resurgence of double-crested cormorants in the Great Lakes 

basin has been accompanied by requests for the U.S. Fish and Wildlife Service, 

U.S. Department of Agriculture/ Wildlife Services, and state fish and wildlife 

management agencies to act. Each agency has a different role to play. The 

primary responsibility of the U.S. Fish and Wildlife Service is regulatory oversight, 

to ensure that actions taken by the states will not cumulatively jeopardize 

cormorant populations. Because the birds are protected under the Migratory Bird 

Treaty Act, their nests and eggs cannot be disturbed, and the birds cannot be 

captured or shot, unless a depredation permit is first obtained from the Service. 

At the federal level, the Service does not conduct on-the-ground management 

activities when cormorants cause damage. This role is the responsibility of the 

U.S. Department of Agriculture’s Wildlife Services Program. Their job is to help 

states, organizations, and individuals resolve conflicts between people and 

wildlife on public and private lands, by either recommending or implementing 

wildlife damage management options. The U.S. Fish and Wildlife Service does 

not act on a request for a depredation permit until the U.S. Department of 

Agriculture recommends this action.

Management Activities

Federal and state fish and wildlife agencies have responded to public and private 

concerns about double-crested cormorants in the Great Lakes basin. The U.S. 

Fish and Wildlife Service has funded Great Lakes-wide population monitoring 

surveys in coordination with states and the Canadian Wildlife Service. The 

agency has issued a regulation permitting the lethal take of cormorants, without a 

permit, on catfish and bait fish farms in 12 southeastern states and Minnesota, 

where economic impacts have been well-documented and non-lethal control has 

proven ineffective. The Service has also funded a variety of studies to assess the 

impact of cormorants on fish populations, and has conducted an extensive 

review of other studies.

The State of New York has altered fish stocking methods in response to 

recommendations from a citizen’s task force. It has also requested and received 

depredation permits for double-crested cormorant control from the U.S. Fish and 

Wildlife Service to prevent nesting colonies from becoming established on new 

islands in Lake Ontario, and to prevent the colony on Oneida Lake from 

jeopardizing the nesting habitat of common terns, a state-listed threatened 

species. The U.S. Department of Agriculture and the State of New York have 

conducted a pilot study to investigate techniques to change migration and 

roosting patterns of double-crested cormorants on Oneida Lake. The U.S. Fish 
and Wildlife Service has also issued depredation permits to the State of Vermont 

to prevent cormorant colonies from spreading to new islands in Lake Champlain 

in order to reduce competition with other colonial waterbirds, and to prevent 

private property damage. To assist the State, the U.S. Department of Agriculture 

has conducted a variety of both lethal and non-lethal cormorant management 

activities on the lake.

What Comes Next?

The U.S. Fish and Wildlife Service will cooperate with state and federal fish and 

wildlife management agencies to develop a regional management plan for 

double-crested cormorants. While the plan is being developed, the Service is 

preparing a comprehensive assessment of the population status of cormorants, 

and a review of the impacts of double-crested cormorants on commercial and 

sport fish populations in both natural and artificial settings. Although it is not the 

current policy of the Service to issue depredation permits to reduce cormorant 

predation on sport fish, permit requests may be considered under unique 

circumstances. Any significant policy changes must be based on sound science, 

and would be implemented only after coordination with appropriate federal and 

state resource agencies and the concerned public.

For Further Information

Additional information on double-crested cormorants is available on the Internet 

at the following websites:

McMaster University

http://www.science.mcmaster.ca/Biology/Harbour/SPECIES/CORMRNT/CORMR

NT.HTM

U.S. Department of Agriculture/Animal and Plant Health Inspection 

Service/Wildlife Services

http://www.aphis.usda.gov/wildlife_damage/nwrc/symposia/cormorant_symposiu

m/index.shtml

U.S. Fish and Wildlife Service/Lake Champlain Fish and Wildlife Resources 

Complex

http://www.fws.gov/r5lcfwro/corfct.htm

U.S. Fish and Wildlife Service/Office of Migratory Bird Management:

http://migratorybirds.fws.gov/issues/cormorant/cormorant.html
U.S. Geological Survey/Patuxent Wildlife Research Center

http://www.mbr-pwrc.usgs.gov/id/mlist/h1200.html

http://www.mbr-pwrc.usgs.gov/bbs/htm96/trn626/tr1200.html