Cormorants and Anhingas (Phalacrocoracidae)
Cormorants and anhingas
(Phalacrocoracidae)
Class Aves
Order Pelecaniformes
Suborder Pelecani
Family Phalacrocoracidae
Thumbnail description
Sleek, dark-colored, large to medium-sized, long-necked waterbirds with all toes joined by webs (totipalmate); they pursue their prey (usually fish) underwater and often stand with wings spread to dry their poorly oiled, wettable plumage
Size
Variation among species ranges from 19 to 40 in (48–102 cm) and weight 1.5–7.7 lb (0.7–3.5 kg)
Number of genera, species
3 genera; 40 species
Habitat
Occur in freshwater ponds, lakes, rivers, and estuaries and in coastal marine waters
Conservation status
Endangered: 2 species; Vulnerable: 8 species; Near Threatened: 5 species
Distribution
Worldwide distribution in suitable habitat in the boreal, temperate, and tropical zones
Evolution and systematics
The 36 species of cormorants (also known as shags) and four of anhingas (also known as darters or snakebirds) make up the family Phalacrocoracidae. They are related to pelicans, frigatebirds, gannets, and tropicbirds, which are also waterbirds in the order Pelecaniformes. The Pelecaniformes lineage is ancient, with a fossil record extending to the Lower Eocene (>54 million years ago). Although cormorants and anhingas are considered here within one family, some taxonomists place anhingas in a separate family, the Anhingidae. Most taxonomists assign all of the cormorants to one genus, Phalacrocorax. Others, however, assign the flightless cormorant (Nannopterum species) and the pygmy cormorants (Halietor species) to separate genera.
Physical characteristics
Cormorants are sleek, large to medium-sized, long-necked waterbirds. The typical body length is 19–40 in (48–102 cm) and they weigh 1.5–7.7 lb (0.7–3.5 kg). The wings are relatively short and angular, and the spread tail is long and wedge-shaped. Cormorants are well adapted to flying and swimming, but because their legs are placed well-back on the body, they are rather clumsy when walking. When in the water, cormorants sit rather low because their bones are quite dense, with few air spaces, and their feathers are not well-oiled and so get wet when immersed. The bill of cormorants is rather thin and tubular, hooked at the tip, and is lacking in external nares (or nostrils); the edges of the bill have tooth-like serrations. The head and upper neck have powerful muscles for closing the bill; these originate in part from special long, sesamoid bones behind the back of the head and are used to maintain a tight grip on slippery fish that have been caught (the beak serrations are also useful in this regard). For many species, the head has a plumage crest during the breeding season. Cormorant species of the Northern Hemisphere are colored glossy blackish, while those of the Southern Hemisphere tend to have a grayish body with white underparts and some black markings. Males are usually somewhat larger than females; otherwise, the sexes look alike, although they may differ in behavior, at least during the breeding season.
Anhingas are even sleeker, longer-necked waterbirds than cormorants. The typical body length is 34–36 in (86–92 cm). The bill is long, sharply pointed, and bright yellow. The wings are relatively short and rounded, and the long tail is wedge-shaped when spread. The legs are placed well-back on the body. The sexes differ in both plumage and aspects of behavior. Male anhingas have an overall black body coloration, with white markings on the wings and neck. Females also have a black body, but a light-brown neck and head. Anhingas are skilled at flying and swimming, but are clumsy on land. Like cormorants, anhingas sit low in the water because of their dense bones and feathers that get wet when immersed.
Distribution
Cormorants are widely distributed over most of the world, with species ranging from the boreal zones to the tropics (except for some Pacific islands). Anhingas occur widely in tropical and subtropical regions.
Habitat
Cormorants inhabit freshwater wetlands, swamps, lakes, rivers, estuaries, and coastal waters. Anhingas occur in freshwater wetlands, swamps, lakes, rivers, and estuaries.
Behavior
Northern species of cormorants are migratory, breeding in northern parts of their range and wintering to the south. Northern populations of anhingas are also migratory. Both cormorants and anhingas are rather gregarious, often occurring in flocks and breeding in colonies. Cormorants fly somewhat directly, often close to the water surface, using strong, steady wingbeats. They also commonly fly in groups that arrange themselves in lines or V-shaped flocks for better aerodynamic efficiency. Anhingas are also strong fliers, and they soar well, sometimes at great altitude. After swimming, both cormorants and anhingas sit on exposed perches with wings spread to the sun to dry their plumage, which lacks oily repellants and thus gets soaking wet when immersed. Cormorants and anhingas are strong swimmers and pursue prey underwater using their feet for propulsion.
Feeding ecology and diet
Cormorants and anhingas feed mostly on fish, but may also eat frogs, large crustaceans, and squid. They catch prey by an agile, underwater pursuit. Cormorants catch their prey in the bill, while anhingas often spear their quarry.
Reproductive biology
Cormorants and anhingas often breed in colonies. They build awkward stick-nests in trees or sometimes on cliffledges. Nests of cormorants can be rather messy, being littered with seaweed, fish remains, and other debris. Cormorants and anhingas lay two to four, elongated, chalky-surfaced eggs which are pale green or blue. Both sexes incubate the eggs (23–25 days) and rear the young. Sexual maturity is generally reached in the third or fourth year.
Conservation status
The IUCN lists 15 species of cormorants as being at risk. Of these, two are Endangered: the flightless or Galapagos cormorant (Nannopterum harrisi) and the Chatham Island shag (P. onslowi). Another eight species are Vulnerable: the Campbell Island shag (P. campbelli), the New Zealand king shag (P. carunculatus), the Stewart Island shag (P. chalconotus), the Aukland Island shag (P. colensoi), the Pitt Island shag (P. featherstoni), the bank cormorant (P. neglectus), the Socotra cormorant (P. nigrogularis), and the Bounty Island shag (P. ranfurlyi). Four species are considered at Lower Risk, Near
Threatened: the pygmy cormorant (P. pygmeus), the redlegged cormorant (P. gaimardi), the crowned cormorant (P. coronatus), and the Cape cormorant (P. capensis). One species, the Pallas's cormorant (Phalacrocorax perspicillatus), is recently extinct. Almost all of these rare cormorants are endemic species, meaning they only occur in relatively small populations
on one or a few isolated, oceanic islands. Endemic species are often at an inherently high risk of extinction. The oriental anhinga (or oriental darter; Anhinga melanogaster) is also listed by the IUCN as being at Lower Risk.
Significance to humans
In some regions where cormorants are abundant, they may be viewed as "pests" by human fishers because they are perceived to be catching "too many fish." In almost all of these cases, however, the cormorants are feeding on smaller species or size-classes of fish than the human fishers are seeking, and so are not in much direct competition. Sometimes, cormorants nesting in colonies kill their nesting trees with their caustic excrement, which may also be perceived to be a local management problem. Several species of cormorants are extremely abundant off parts of Peru and Chile, such that their excrement and that of other abundant seabirds is collected from desert islands as a phosphorus- and nitrogen-rich fertilizer known as guano. Several local Japanese cultures have learned to use tame cormorants to catch fish for the market. In these cases, the cormorants are tethered by a leg and are prevented from swallowing fish they catch by a soft noose or collar tied loosely around their throat. Cormorants and anhingas are also sought for observation by birders and other naturalists, and so contribute to local economic benefits through ecotourism. This is especially true of the rarer species.
Species accounts
List of Species
Great cormorantDouble-crested cormorant
Brandt's cormorant
Pelagic cormorant
Olivaceous cormorant
New Zealand king shag
Galapagos cormorant
American anhinga
Great cormorant
Phalacrocorax carbo
taxonomy
Pelecanus carbo Linnaeus, 1758, Europe. Six subspecies.
other common names
English: Black cormorant, white-breasted cormorant; French: Grand Cormoran; German: Kormoran; Spanish: Cormorán Grande.
physical characteristics
This largest species of cormorant has a body length of about 37 in (93 cm), with a pale yellow bill, pale yellow cheek pouch bordered by a white throat, glossy blackish plumage, black legs and feet, and males somewhat larger than females (males: 5.1 lb (2.3 kg); females: 4.2 lb (1.9 kg).
distribution
A very widespread species in temperate regions of the world, occurring locally in the Northwest Atlantic of North America, more widely through Eurasia, and in parts of Southeast Asia, Africa, and Australia. They generally winter near their breeding grounds.
habitat
Nests on seacliffs, feeds in coastal waters.
behavior
A highly social species that breeds in colonies and aggregates in flocks. Like all cormorants, it catches fish by underwater pursuit.
feeding ecology and diet
Feeds on small fish, crustaceans, and squid.
reproductive biology
Lays three to four eggs in a crude stick-nest on a cliff ledge, with both sexes sharing the incubation (27–31 days) and rearing of the chicks.
conservation status
Not threatened. Rather abundant over much of its range.
significance to humans
None Known.
Not of great importance to humans over most of the range; however, in Japan this is one of two species (the other is the Japanese cormorant, Phalacrocorax capillatus) trained by human fishers to help them catch fish.
Double-crested cormorant
Phalacrocorax auritus
taxonomy
Carbo auritus Lesson, 1831, North America. Four subspecies.
other common names
French: Cormoran à aigrettes; German: Ohrenscharbe; Spanish: Cormorán Orejudo.
physical characteristics
Body length of 33 in (83 cm), with a bright yellow bill, yellow cheek pouch, blue eyes, glossy blackish plumage, black legs and feet, and males somewhat larger than females.
distribution
The most widely distributed cormorant in North America, occurring on both the Pacific and Atlantic coasts, in the Caribbean Sea, and on many larger inland lakes and rivers.
habitat
Usually nests on islands and feeds in coastal waters and in large lakes and rivers.
behavior
A highly social species that breeds in colonies and aggregates in flocks; it catches its prey by underwater pursuit.
feeding ecology and diet
Feeds on small fish, crayfish, squid, and other crustaceans.
reproductive biology
Lays three to four eggs in a crude stick-nest located in a tree, with both sexes sharing the incubation (c. 25–29 days) and rearing of the chick.
conservation status
Not threatened. Abundant over much of its range. However, this species was considered at risk in some states in the 1970s due to organochlorine-pesticide-induced egg-shell thinning and population declines. These populations are now increasing in numbers following bans on the use of these chemicals.
significance to humans
In some parts of its range it is considered a pest for "eating too many fish" and because it kills its nesting trees with its caustic excrement.
Brandt's cormorant
Phalacrocorax penicillatus
taxonomy
Carbo penicillatus Brandt, 1837, no locality. Monotypic.
other common names
English: Brown's cormorant, Townsend's cormorant; French: Cormoran de Brandt; German: Pinselscharbe; Spanish: Cormorán Sargento.
physical characteristics
Body length of 29 in (74 cm), with a grayish bill, blue cheek pouch, yellow throat patch, glossy blackish plumage, and black legs and feet.
distribution
Occurs along the Pacific coast of North America, from southern Alaska to Baja California.
habitat
Nests in trees and feeds in coastal waters.
behavior
A social species that breeds in colonies and aggregates in flocks.
feeding ecology and diet
Feeds on small fish, squid, and crustaceans.
reproductive biology
Lays three to four eggs in a crude stick-nest, with both sexes sharing the incubation and rearing of the chick. One or two chicks per nest normally fledge.
conservation status
Not threatened. Abundant over much of its range.
significance to humans
Pelagic cormorant
Phalacrocorax pelagicus
taxonomy
Phalacrocorax pelagicus Pallas, 1811, eastern Kamachatka and the Aleutian Islands. Two subspecies.
other common names
English: Baird's cormorant, pelagic shag; French: Cormoran pélagique; German: Meerscharbe; Spanish: Cormorán Pelágico.
physical characteristics
Body length of 22 in (56 cm), with a dark bill, red cheek pouch and throat patch, glossy blackish plumage, and black legs and feet.
distribution
Occurs along the Pacific coast of North America, from the top of Baja California through to northwestern Alaska, across the Aleutians to eastern Siberia, and south to northern Honshu Island, Japan, plus most Beringian waters in between.
habitat
Nests on cliff-ledges and in trees and feeds in coastal waters.
behavior
A social species that breeds in colonies and aggregates in flocks.
feeding ecology and diet
Feeds on small fish, squid, and crustaceans.
reproductive biology
Lays three to four eggs in a crude nest, with both sexes sharing the incubation (c. 31 days) and rearing of the chick.
conservation status
Not threatened. Abundant over much of its range.
significance to humans
None known.
Olivaceous cormorant
Phalacrocorax olivaceus
taxonomy
Pelecanus olivaceus Humboldt, 1805, banks of the Magdalena River, Colombia. Two subspecies.
other common names
English: Neotropic cormorant; French: Cormoran vigua; German: Biguascharbe; Spanish: Cormorán Biguá.
physical characteristics
Body length of 25 in (63 cm), with a bright yellow bill, yellow cheek pouch, white band behind the lower mandible, glossy blackish plumage, black legs and feet, and males somewhat larger than females.
distribution
Occurs from the U.S. Gulf of Mexico through the Caribbean, Mexico, Central America, and almost all of South America.
habitat
Nests in trees near freshwater; feeds in coastal waters and in large lakes and rivers.
behavior
A social species that breeds in colonies and aggregates in flocks.
feeding ecology and diet
Feeds on small fish, crayfish, and other aquatic animals.
reproductive biology
Lays three to four eggs in a crude stick-nest located in a tree, with both sexes sharing the incubation (c. 30 days) and rearing of the chick.
conservation status
Not threatened. Abundant over much of its range.
significance to humans
None known.
New Zealand king shag
Phalacrocorax carunculatus
taxonomy
Pelecanus carunculatus Gmelin, 1789, Queen Charlotte Sound, New Zealand, and Staten Island. Monotypic.
other common names
English: Bronzed shag; rough-faced cormorant; rough-faced shag; French: Cormoran caronculé; German: Warzenscharbe; Spanish: Cormorán Carunculado.
physical characteristics
Body length of 30 in (76 cm), with a reddish yellow bill, white throat and belly, glossy blackish plumage on the back and wings, and pink legs and feet.
distribution
An endemic (or local) species that only breeds on a few islands in Cook Strait between North and South Islands of New Zealand.
habitat
Nests on cliff-ledges and feeds in nearby coastal waters.
behavior
A social species that breeds in colonies and aggregates in small flocks.
feeding ecology and diet
Feeds on small fish, squid, and crustaceans.
reproductive biology
Lays one to three eggs in a crude nest, with both sexes sharing the incubation and rearing of the chick.
conservation status
A rare species, listed as Vulnerable due to limited habitat.
significance to humans
Not of much direct importance to people, but sightings are sought after by naturalists, which brings some economic benefits through ecotourism.
Galapagos cormorant
Nannopterum harrisi
taxonomy
Phalacrocorax harrisi Rothschild, 1898, Narborough Island, Galapagos Archipelago. Monotypic.
other common names
English: Flightless cormorant; French: Cormoran aptère; German: Galapagosscharbe; Spanish: Cormorán Mancón.
physical characteristics
Body length 36–39 in (91–99 cm), with short, stubby, raggedappearing wings, an almost all-black plumage, black legs and feet, and a pinkish throat pouch.
distribution
An endemic (or local) species of the Galapagos Islands in the Pacific Ocean off equatorial South America.
habitat
Occurs in nearshore coastal waters.
behavior
A flightless species that roosts on rocks during the night and rarely wanders far from the place where born.
feeding ecology and diet
Catches its prey of fish, squid, and crustaceans by an agile underwater pursuit.
reproductive biology
Lays two to three eggs on a rocky ledge; both sexes incubate the eggs (c. 35 days) and care for the young.
conservation status
An Endangered species subject to severe fluctuations in numbers in response to El Nino-related marine perturbations, with fewer than 1,000 breeding pairs surviving at only two breeding sites.
significance to humans
Not of much direct importance to people, but contributes to local economic benefits through ecotourism associated with seeing rare birds and other wildlife of the Galapagos Islands.
American anhinga
Anhinga anhinga
taxonomy
Plotus anhinga Linnaeus, 1766, Rio Tapajós, Pará, Brazil. Two subspecies.
other common names
English: Anhinga, American darter, snakebird; French: Anhinga d'Amérique; German: Amerikanischer Schlangenhalsvogel; Spanish: Anhinga Americana.
physical characteristics
Body length 34 in (85 cm), with a small head, relatively short wings, web-shaped tail, yellowish pointed beak, and yellowish legs and feet; male is colored overall black with silvery-white markings on the upper wings, while female has a brown head, neck, and upper chest.
distribution
Southeastern United States, Central America, South America south to northern Argentina.
habitat
Warm-temperate, subtropical, and tropical wetlands, rivers, lakes, swamps, and estuaries.
behavior
Flies in a flap-and-glide manner, and often soars; often swims largely submerged, with only the head and neck exposed (this is how it got its common name, "snakebird"); roosts in trees, and dries its wet plumage by spreading its wings to the sun.
feeding ecology and diet
Catches and spears its prey of fish, crayfish, and amphibians by agile underwater pursuit. Tosses speared prey into the air with a flick of the head, then catches the prey in mid-air to swallow head-first.
reproductive biology
Tends to breed in colonies; lays one to five eggs in a bulky stick-nest in a tree near water. Both sexes incubate the eggs (25–28 days) and care for the young.
conservation status
Not threatened. Abundant throughout its range.
significance to humans
Not of much direct importance to humans, but often a favorite species of naturalists.
Resources
Books
Cramp, S., and K.E.L. Simmons, eds. The Birds of the Western Palearctic. Vol. 1, Ostrich to Ducks. Oxford: Oxford University Press, 1977.
Orta, J. "Family Phalacrocoracidae (Cormorants)." In Handbook of the Birds of the World. Vol. 1, Ostrich to Ducks, edited by Josep del Hoyo, Andrew Elliott, and Jordi Sargatal. Barcelona: Lynx Edicions, 1992.
Orta, J. " Family Anhingidae (Darters)." In Handbook of the Birds of the World. Vol. 1, Ostrich to Ducks, edited by Josep del Hoyo, Andrew Elliott, and Jordi Sargatal. Barcelona: Lynx Edicions, 1992.
Periodicals
Hennemann, W.W. "Spread-winged Behavior of Double-crested and Flightless Cormorants, Phalacrocorax auritus and P. harrisi: Wing Drying or Thermoregulation?" Ibis 126(1984): 230–239.
Jackson, J.A., and B.J.S. Jackson. "The Double-crested Cormorant in the South-central United States: Habitat and Population Changes of a Feathered Pariah. " Colonial Waterbirds 18 (special publ. no. 1) (1995): 118–130.
Mahoney, S.A. "Plumage Wettability of Aquatic Birds." Auk 101 (1984): 181–185.
Organizations
BirdLife International. Wellbrook Court, Girton Road, Cambridge, Cambridgeshire CB3 0NA United Kingdom. Phone: +44 1 223 277 318. Fax: +44-1-223-277-200. E-mail: [email protected] Web site: <http://www.birdlife.net>
IUCN–The World Conservation Union. Rue Mauverney 28, Gland, 1196 Switzerland. Phone: +41-22-999-0001. Fax: +41-22-999-0025. E-mail: [email protected] Web site: <http://www.iucn.org>
Bill Freedman, PhD