Double-crested Cormorant
Encyclopedia
The Double-crested Cormorant (Phalacrocorax auritus) is a member of the cormorant
family of seabird
s. It occurs along inland waterways as well as in coastal areas, and is widely distributed across North America
, from the Aleutian Islands in Alaska
down to Florida
and Mexico
. Measuring 70–90 cm (28–35 in) in length, it is an all-black bird which gains a small double crest of black and white feathers in breeding season. It has a bare patch of orange-yellow facial skin. Five subspecies are recognized.
The Double-crested Cormorant is found near rivers, lakes and along the coastline. It mainly eats fish
and hunts by swimming and diving. Its feathers, like those of all cormorants, are not waterproof and it must spend time drying them out after spending time in the water. Once threatened by use of DDT, the numbers of this bird have increased markedly in recent years.
words φαλακρος (phalakros), 'bald' and κοραξ (korax), 'crow' or 'raven,' and the Latin
auritus, 'eared,' referring to its nuptial crests. Its common name refers to the same nuptial crests. Other common names of this species include Crow-duck, Lawyer, Nigger
Goose, Shag and Taunton Turkey (in New England
).
Five subspecies are recognized:
The Double-crested Cormorant is a large waterbird with a stocky body, long neck, medium-sized tail, webbed feet and a medium sized hooked bill. It has a body length of between 70–90 cm (28–35 in) long, with a wingspan of between 114–132 cm (45–52 in). Double-crested Cormorants weigh between 1.2–2.5 kg (2.6–5.5 pounds) Males and females do not display sexual dimorphism
.
This species has dark-colored plumage with bare super-loral skin and gular skin
that is yellow or orange. An adult in breeding plumage will be mostly black with the back and coverts
being a dark grayish towards the center. Nuptial crests, for which the species is named, are either white, black or a mix of the two. These are located just above the eyes with the bare skin on the face of a breeding adult being orange. A non-breeding adult will lack the crests and have more yellowish skin around the face. The bill of the adult is dark-colored.
The plumage of juvenile Double-crested Cormorants is more dark grey or brownish. The underparts of a juvenile are lighter than the back with a pale throat and breast that darkens towards the belly. As a bird ages, its plumage will grow darker. The bill of a juvenile will be mostly orange or yellowish.
(on the west coast) and southern New England
(on the east coast). It can be found as far south as Mexico
and the Bahamas. It migrates
from the coldest parts of its breeding range, such as eastern Canada
, and has occurred in Europe
as a very rare vagrant, for example in Great Britain
, Ireland
, and the Azores
.
The Double-crested Cormorant swims low in the water, often with just its neck and head visible, and dives from the surface. It uses its feet for propulsion and is able to dive to a depth of 1.5–7.5 m (5–25 feet) for 30–70 seconds. After diving, it spends long periods standing with its wings outstretched to allow them to dry, since they are not fully waterproofed. This species flies low over the water, with its bill tilted slightly upward, sometimes leaving the colony in long, single-file lines.
, but will sometimes also eat amphibian
s and crustacean
s. Fish are caught by diving under water. Smaller fish may be eaten while the bird is still beneath the surface but bigger prey is often brought to the surface before it is eaten.
Cormorants regurgitate pellets containing undigested parts of their meals such as bones. These pellets can be dissected by biologists in order to discover what they ate.
Breeding occurs in coastal areas as well as near inland rivers and lakes. They build stick nests in trees, on cliff edges, or on the ground on suitable islands. They are gregarious birds usually found in colonies, often with other aquatic birds, and have a deep, guttural grunt call.
. Colonies have also been persecuted from time to time in areas where they are thought to compete with human fishing.
Recently the population of Double-crested Cormorants has increased. Some studies have concluded that the recovery was allowed by the decrease of contaminants, particularly the discontinued use of DDT. The population may have also increased because of aquaculture ponds in its southern wintering grounds. The ponds favor good over-winter survival and growth.
In 1894, Thomas McIlwraith in his book, Birds of Ontario, concludes his section on Double-crested Cormorants by saying: “When the young are sufficiently grown, they gather into immense flocks in unfrequented sections, and remain until the ice-lid has closed over their food supply, when they go away, not to return till the cover is lifted up in the spring.”
For populations nesting in the Great Lakes
region, it is believed that the colonization of the lakes by the non-native alewife
(a small prey fish) has provided optimal feeding conditions and hence good breeding success. Double-crested cormorants eat other species of fish besides alewives and have been implicated in the decline of some sport-fish
populations in the Great Lakes and other areas. Scientists are not in agreement about the exact extent of the role of cormorants in these declines, but some believe that Double-crested Cormorants may be a factor for some populations and in some locations.
In light of this belief, and because of calls for action by the public, the United States Fish and Wildlife Service
(the U.S. Federal government agency charged with their protection) has recently extended control options to some other government entities. This includes culling
of populations and measures to thwart reproduction, in an effort to control their growing numbers.
The U.S. Fish and Wildlife Service retains oversight and the control measures are not extended to the general public (no hunting season). Many government agencies at different levels in both the U.S. and Canada continue to wrestle with how best to respond to the situation.
In May 2008, the Canadian government reduced significantly the number of nests of the birds on Middle Island, a small island in Lake Erie
and part of Point Pelee National Park. This is an attempt to keep the small island in balance and preserve its vegetation but opponents to he plan have pointed out that it is based on faulty information, provided in part by anglers who view cormorants as competitors.
Cormorant
The bird family Phalacrocoracidae is represented by some 40 species of cormorants and shags. Several different classifications of the family have been proposed recently, and the number of genera is disputed.- Names :...
family of seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s. It occurs along inland waterways as well as in coastal areas, and is widely distributed across North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, from the Aleutian Islands in Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
down to Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. Measuring 70–90 cm (28–35 in) in length, it is an all-black bird which gains a small double crest of black and white feathers in breeding season. It has a bare patch of orange-yellow facial skin. Five subspecies are recognized.
The Double-crested Cormorant is found near rivers, lakes and along the coastline. It mainly eats fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and hunts by swimming and diving. Its feathers, like those of all cormorants, are not waterproof and it must spend time drying them out after spending time in the water. Once threatened by use of DDT, the numbers of this bird have increased markedly in recent years.
Taxonomy
The Double-crested Cormorant was described by Rene Primevere Lesson in 1831. Its scientific name is derived from the GreekAncient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
words φαλακρος (phalakros), 'bald' and κοραξ (korax), 'crow' or 'raven,' and the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
auritus, 'eared,' referring to its nuptial crests. Its common name refers to the same nuptial crests. Other common names of this species include Crow-duck, Lawyer, Nigger
Nigger
Nigger is a noun in the English language, most notable for its usage in a pejorative context to refer to black people , and also as an informal slang term, among other contexts. It is a common ethnic slur...
Goose, Shag and Taunton Turkey (in New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
).
Five subspecies are recognized:
- P. a. albociliatus (Ridgway 1884), Farallon Cormorant, breeds along the Pacific coast of North America from British ColumbiaBritish ColumbiaBritish Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
to Bird Island in the state of SinaloaSinaloaSinaloa officially Estado Libre y Soberano de Sinaloa is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 18 municipalities and its capital city is Culiacán Rosales....
, MexicoMexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
and possibly even further south. Significant colonies of these birds may also be found further inland including areas around the Salton SeaSalton SeaThe Salton Sea is a shallow, saline, endorheic rift lake located directly on the San Andreas Fault, predominantly in California's Imperial Valley. The lake occupies the lowest elevations of the Salton Sink in the Colorado Desert of Imperial and Riverside counties in Southern California. Like Death...
. According to currently available information, this subspecies is the third largest among the subspecies of the Double-crested Cormorant. Historical records indicate that this species was far more abundant in the past, but due to human persecution and development in their breeding range, the population of this subspecies has declined. The largest colony of cormorants in North America consisted of members of this subspecies at San Martin Island, Baja CaliforniaBaja CaliforniaBaja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, Mexico, and was recorded in 1913. Physically, this subspecies is fairly large and has white to partially white nuptial crests. - P. a. auritus (Lesson, 1831), this, the nominate subspecies, has the largest and most widespread breeding population. It ranges from the Great BasinGreat BasinThe Great Basin is the largest area of contiguous endorheic watersheds in North America and is noted for its arid conditions and Basin and Range topography that varies from the North American low point at Badwater Basin to the highest point of the contiguous United States, less than away at the...
and Rocky MountainsRocky MountainsThe Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
east into central and eastern North America. This region includes the Canadian prairiesCanadian PrairiesThe Canadian Prairies is a region of Canada, specifically in western Canada, which may correspond to several different definitions, natural or political. Notably, the Prairie provinces or simply the Prairies comprise the provinces of Alberta, Saskatchewan, and Manitoba, as they are largely covered...
and the Great LakesGreat LakesThe Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
. Historically, this subspecies has bred in abundance across most of this region, though there are questions as to if this bird has always bred in the Great Lakes region. Some evidence indicates that the bird has only begun breeding in the region since the eary 20th century while other evidence suggests that it has been breeding in the region much longer. Physically, this subspecies is moderately large and has black nuptial crests. - P. a. cincinnatus (BrandtJohann Friedrich von BrandtJohann Friedrich von Brandt was a German naturalist.Brandt was born in Jüterbog and educated at a gymnasium in Wittenberg and the University of Berlin. In 1831 he was appointed director of the Zoological Department at the St Petersburg Academy of Sciences, where he published in Russian...
1837), White-crested Cormorant, currently, this is the most restricted subspecies, geographically, and it has the smallest population of Double-crested Cormorant subspecies. It is found along the southern coast of AlaskaAlaskaAlaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
and on the Aleutian Islands, ranging west from KodiakKodiak, AlaskaKodiak is one of 7 communities and the main city on Kodiak Island, Kodiak Island Borough, in the U.S. state of Alaska. All commercial transportation between the entire island and the outside world goes through this city either via ferryboat or airline...
to Chuginidak in the Aleutians. Historically, the range extended west to the Near IslandsNear IslandsThe Near Islands or Sasignan Islands are the smallest and westernmost group of the Aleutian Islands in southwestern Alaska.-Geography:The largest of the Near Islands are Attu and Agattu...
, but possibly due to nest predation by introducedIntroduced speciesAn introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
foxFoxFox is a common name for many species of omnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail .Members of about 37 species are referred to as foxes, of which only 12 species actually belong to...
es, the birds were no longer breeding in the area by the mid-1930s. Physically, this subspecies is the largest and it bears straight, white nuptial crests. - P. a. floridanus (AudubonJohn James AudubonJohn James Audubon was a French-American ornithologist, naturalist, and painter. He was notable for his expansive studies to document all types of American birds and for his detailed illustrations that depicted the birds in their natural habitats...
1835), Florida Cormorant, the smallest of the five subspecies, it is found from southern and central TexasTexasTexas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
east to the Atlantic and from North CarolinaNorth CarolinaNorth Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
south to FloridaFloridaFlorida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
. Records indicate that this subspecies was abundant throughout its range before the 20th century, but now is only abundant in Florida. This bird has dark nuptial crests. - P. a. heuretus Physically, this subspecies is the largest and it bears straight, white nuptial crests.
Description
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
.
This species has dark-colored plumage with bare super-loral skin and gular skin
Gular skin
Gular skin , in ornithology, is an area of featherless skin on birds that joins the lower mandible of the beak to the bird's neck....
that is yellow or orange. An adult in breeding plumage will be mostly black with the back and coverts
Covert (feather)
A covert feather on a bird is one of a set of feathers, called coverts, which as the name implies, cover other feathers. The coverts help to smooth airflow over the wings and tail.- Wing-coverts :...
being a dark grayish towards the center. Nuptial crests, for which the species is named, are either white, black or a mix of the two. These are located just above the eyes with the bare skin on the face of a breeding adult being orange. A non-breeding adult will lack the crests and have more yellowish skin around the face. The bill of the adult is dark-colored.
The plumage of juvenile Double-crested Cormorants is more dark grey or brownish. The underparts of a juvenile are lighter than the back with a pale throat and breast that darkens towards the belly. As a bird ages, its plumage will grow darker. The bill of a juvenile will be mostly orange or yellowish.
Distribution and habitat
A very common and widespread species, it winters anywhere that is ice-free along both coasts, as far north as southern AlaskaAlaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
(on the west coast) and southern New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
(on the east coast). It can be found as far south as Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
and the Bahamas. It migrates
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
from the coldest parts of its breeding range, such as eastern Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, and has occurred in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
as a very rare vagrant, for example in Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
, Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
, and the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
.
Behavior
Diet
Food can be found in the sea, freshwater lakes, and rivers. Like all cormorants, the double-crested dives to find its prey. It mainly eats fishFish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, but will sometimes also eat amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s. Fish are caught by diving under water. Smaller fish may be eaten while the bird is still beneath the surface but bigger prey is often brought to the surface before it is eaten.
Cormorants regurgitate pellets containing undigested parts of their meals such as bones. These pellets can be dissected by biologists in order to discover what they ate.
Breeding
Recovery
The Double-crested Cormorant's numbers decreased in the 1960s due to the effects of DDTDDT
DDT is one of the most well-known synthetic insecticides. It is a chemical with a long, unique, and controversial history....
. Colonies have also been persecuted from time to time in areas where they are thought to compete with human fishing.
Recently the population of Double-crested Cormorants has increased. Some studies have concluded that the recovery was allowed by the decrease of contaminants, particularly the discontinued use of DDT. The population may have also increased because of aquaculture ponds in its southern wintering grounds. The ponds favor good over-winter survival and growth.
In 1894, Thomas McIlwraith in his book, Birds of Ontario, concludes his section on Double-crested Cormorants by saying: “When the young are sufficiently grown, they gather into immense flocks in unfrequented sections, and remain until the ice-lid has closed over their food supply, when they go away, not to return till the cover is lifted up in the spring.”
For populations nesting in the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
region, it is believed that the colonization of the lakes by the non-native alewife
Alewife
The alewife is a species of herring. There are anadromous and landlocked forms. The landlocked form is also called a sawbelly or mooneye...
(a small prey fish) has provided optimal feeding conditions and hence good breeding success. Double-crested cormorants eat other species of fish besides alewives and have been implicated in the decline of some sport-fish
Angling
Angling is a method of fishing by means of an "angle" . The hook is usually attached to a fishing line and the line is often attached to a fishing rod. Fishing rods are usually fitted with a fishing reel that functions as a mechanism for storing, retrieving and paying out the line. The hook itself...
populations in the Great Lakes and other areas. Scientists are not in agreement about the exact extent of the role of cormorants in these declines, but some believe that Double-crested Cormorants may be a factor for some populations and in some locations.
In light of this belief, and because of calls for action by the public, the United States Fish and Wildlife Service
United States Fish and Wildlife Service
The United States Fish and Wildlife Service is a federal government agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats...
(the U.S. Federal government agency charged with their protection) has recently extended control options to some other government entities. This includes culling
Culling
Culling is the process of removing animals from a group based on specific criteria. This is done either to reinforce certain desirable characteristics or to remove certain undesirable characteristics from the group...
of populations and measures to thwart reproduction, in an effort to control their growing numbers.
The U.S. Fish and Wildlife Service retains oversight and the control measures are not extended to the general public (no hunting season). Many government agencies at different levels in both the U.S. and Canada continue to wrestle with how best to respond to the situation.
In May 2008, the Canadian government reduced significantly the number of nests of the birds on Middle Island, a small island in Lake Erie
Lake Erie
Lake Erie is the fourth largest lake of the five Great Lakes in North America, and the tenth largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. It is bounded on the north by the...
and part of Point Pelee National Park. This is an attempt to keep the small island in balance and preserve its vegetation but opponents to he plan have pointed out that it is based on faulty information, provided in part by anglers who view cormorants as competitors.
External links
- Double-crested Cormorant Information and Photos - South Dakota Birds and Birding
- Double-crested Cormorant Species Account - Cornell Lab of Ornithology
- Double-crested Cormorant - USGS Patuxent Bird Identification InfoCenter