double-crested cormorant

double-crested cormorant
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Name	Double-crested cormorant
Genus	Nannopterum
Species	auritum
Authority	(Lesson, 1831)

double-crested cormorant The double-crested cormorant is a widespread North American waterbird known for its piscivorous habits and distinctive breeding plumage. It occurs across regions associated with Great Lakes, Mississippi River, Pacific Northwest, Gulf of Mexico, Hudson Bay and frequents habitats managed or influenced by entities such as the U.S. Fish and Wildlife Service, Parks Canada, Environmental Protection Agency, National Audubon Society and local Department of Natural Resources (Minnesota). Populations have been subjects of study by scientists affiliated with institutions including Smithsonian Institution, University of Minnesota, Cornell Lab of Ornithology, NOAA Fisheries and Canadian Wildlife Service.

Taxonomy and systematics

The species was described by René Lesson in 1831 and has been placed in genera including Phalacrocorax and Nannopterum in revisions influenced by molecular work from laboratories at American Museum of Natural History, Museum of Comparative Zoology, Royal Ontario Museum, Natural History Museum, London and research published by teams from University of British Columbia. Subspecific treatments have been compared with forms from Aleutian Islands, Baja California, Great Salt Lake and Chesapeake Bay, and taxonomic decisions reference standards set by groups such as the American Ornithological Society, International Ornithological Committee and regional checklists maintained by the Audubon Society. Evolutionary relationships have been tested alongside genera studied by researchers at Harvard University, University of Kansas, Yale University and molecular labs funded by agencies like the National Science Foundation.

Description

Adults display glossy black plumage with a greenish or bluish sheen and, in breeding season, show the characteristic double crest of tufts on the head; field guides from National Geographic Society, RSPB, Sibley Guides and Peterson Field Guides describe identification features compared across species such as great cormorant and Brandt's cormorant. The species exhibits orange-yellow facial skin and a long hooked bill; museum specimens at Smithsonian National Museum of Natural History, Royal Ontario Museum and California Academy of Sciences illustrate variation among populations from Alaska, Florida, Texas and California. Measurements in ornithological literature from Canadian Journal of Zoology, The Auk and Condor provide morphometrics compared with other waterbirds studied by researchers at Duke University, University of Washington, and Ohio State University.

Distribution and habitat

Range maps produced by organizations including BirdLife International, eBird, NatureServe, U.S. Geological Survey and regional bird atlases show use of inland lakes, coastal estuaries, rivers and reservoirs from Alaska and Yukon through Canada into the contiguous United States and parts of Mexico. Important sites include Great Salt Lake, Chesapeake Bay, San Francisco Bay, Lake Ontario, Lake Erie and Prince William Sound, with seasonal movements documented by banding programs run by U.S. Geological Survey Bird Banding Laboratory, Canadian Bird Banding Office and universities such as University of British Columbia and University of Toronto. Habitat selection is influenced by factors studied by agencies like NOAA, Environment and Climate Change Canada and local authorities such as the New York State Department of Environmental Conservation.

Behavior and ecology

Double-crested cormorants roost and nest in colonies that have been monitored by conservationists from Cornell Lab of Ornithology, Audubon Society of Rhode Island, Manomet, Wetlands International and municipal partners including New York City Parks and Los Angeles County Department of Beaches and Harbors. Social behavior, molt patterns and seasonal movements are topics in research from University of Alaska Fairbanks, Oregon State University, Michigan State University and international collaborators at University of Helsinki and CSIRO. Interactions with predator species such as bald eagle and competitors including double-crested cormorant sympatric species have been observed near colonies documented by the National Park Service, Point Reyes National Seashore and regional wildlife refuges like Chincoteague National Wildlife Refuge.

Feeding and diet

The diet is primarily fish taken by plunge-diving and pursuit underwater, with foraging behavior quantified in studies published in Journal of Wildlife Management, Marine Biology, Canadian Journal of Fisheries and Aquatic Sciences and undertaken by researchers at NOAA Fisheries, University of Florida and University of California, Santa Cruz. Prey composition varies regionally and includes species managed or assessed by agencies such as Great Lakes Fishery Commission, Atlantic States Marine Fisheries Commission, Texas Parks and Wildlife Department and researchers from Rutgers University. Foraging impacts and overlap with commercial or recreational fisheries have prompted assessments by stakeholders including National Marine Fisheries Service, Recreational Boating and Fishing Foundation and state commissions in Michigan and Wisconsin.

Reproduction and lifecycle

Breeding colonies vary from small aggregations to large rookeries; nesting substrates include trees, rock ledges and artificial structures surveyed by biologists from U.S. Fish and Wildlife Service, Parks Canada, California Department of Fish and Wildlife and NGOs like Audubon Society. Clutch size, incubation, chick growth and fledging success have been reported in field studies from institutions such as Cornell University, University of Minnesota, Memorial University of Newfoundland and published in journals including Ornithological Monographs and Ibis. Banding and telemetry projects by the Bird Banding Laboratory and university teams track longevity, dispersal and survival in relation to environmental factors monitored by NOAA, Environment and Climate Change Canada and regional wildlife agencies.

Conservation and human interactions

Conservation status and management have been influenced by historical impacts from organochlorine pesticides documented by researchers at Environmental Protection Agency, University of Michigan and Duke University and by legal and policy actions involving entities such as the U.S. Fish and Wildlife Service, Department of Fisheries and Oceans (Canada), National Oceanic and Atmospheric Administration and state wildlife agencies. Conflicts with aquaculture, commercial fisheries and recreational anglers have led to management plans coordinated by organizations including U.S. Army Corps of Engineers, New York Department of Environmental Conservation, Washington Department of Fish and Wildlife and local stakeholders like Maine Department of Marine Resources. Conservation measures, monitoring, and public outreach are conducted through partnerships among National Audubon Society, BirdLife International, Wildlife Conservation Society, academic researchers and municipal authorities.

Category:Phalacrocoracidae