Double Crested Cormorant (Nannopterum auritum)

double crested cormorant

The double crested cormorant (Nannopterum auritum) is a member of the genus Nannopterum. It is widely distributed around the North Pacific, with an estimated global extent of occurrence of 730,000 km2. This species nests in colonies on cliffs or trees, typically near water.

A large, black bird with long wings and a long neck, the double crested cormorant has an average wingspan of 48 inches and can weigh up to 2.5 kg. It belongs to the family Phalacrocoracidae and is found in Europe, Asia, and Africa as well as New Zealand and Australia, where it is locally known as the Pied Cormorant.

Its name comes from the Latin word cormor, meaning crow, because of its black plumage, which contrasts with its white crest feathers.

It breeds in coastal parts of the Holarctic region and some islands in the Caribbean. The scientific name comes from Ancient Greek nannos duck and pteron wing, an apt description since the wings are short and rounded as in many diving birds, while the feet are webbed as in dabbling ducks such as pochards or mallards.

What is a cormorant?

A cormorant is a large diving bird with a long neck, hooked bill, short web-footed feet, and mostly dark plumage. Breeding typically occurs along coastal cliffs. A cormorant typically lives near the sea and eats fish.

Description

double crested cormorant

 

Double crested cormorants are large waterbirds with a stocky body, long neck, medium-sized tail, webbed feet, and a medium-sized hooked bill. The bird’s upper bill is shaped like a hooked beak, giving it a resemblance to an eagle.

They have black plumage with a bronze-green sheen that becomes glossy in sunlight. Both sexes are alike but males average slightly larger than females. Young birds may have buffier throats and paler heads than adults; they take their adult plumage at three years old.

The Double-crested cormorant is an aquatic bird native to North America, found on both coasts of the continent. It breeds in the Aleutian Islands and Asia across much of North America.

Scientific name

The scientific name of the double crested cormorant is Nannopterum auritum

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Double crested cormorant range and habitat

The Double-crested cormorant is native to North America, including along the Atlantic coast from Massachusetts in the United States to Venezuela. The species is primarily associated with freshwater habitats, though it is occasionally found in coastal saltwater marshes and lagoons.

They can be found in both freshwater rivers and streams as well as marine bays. They live on or near small ponds, lakes, or tidal estuaries where they nest on small rock ledges or floating vegetation mats.

Size and weight

The Double-crested cormorant is about 70 to 90 centimeters long (28 to 35 inches) and weighs about 1.2 to 2.5 kilograms (2.6 to 5.5 lb). It has a wingspan of about 114 to 123 centimeters (45 to 48 inches), which is among the largest for aquatic birds.

Feathers and plumage

double crested cormorant

The Double-crested cormorant has very beautiful plumage. They have a lot of black feathers, which are especially eye-catching against the light blue sky. In addition to having a high and pointed crest, they also have distinctive bands of cream-colored feathers running from the back of their head to the center of their tail.

Their neck feathers are also a different color than their body. On their neck, they are black with streaks of brown. Overall, this bird has such intricate coloring that it can be difficult to spot all the colors at once!

Molting

Double crested cormorants are waterbirds that have wings that propel them through the water. Molting of body feathers occurs primarily in July-Nov; molting of remiges, however, can extend into winter and even spring in some areas.

In order to replace worn feathers, they shed their outer layer of skin in an annual process called molting. These birds only molt one time per year and usually do so near the end of winter or early spring. Double crested cormorants typically stop eating during this time period and will not drink any water.

It is normal for a cormorant to lose between 40-60% of its body weight while it undergoes molting. The bird’s feathers and other features will also change after a successful molt – which is why it looks different from before!

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Nesting behavior

An adult male double crested cormorant selects the nest site and attracts a female. Nests can be on the ground, on rocks or coral reefs without vegetation, or on trees. Trees may be alive when the cormorant colony first forms, but die from guano build-up after a few years. A colony’s nests are built at its center, then expand outward.

Two Double crested Cormorant mates work together to build the nest, with the male bringing most of the materials and the female doing the building. The nest is mostly made up of finger-size sticks, with some seaweed and flotsam. It is lined with grass.

Ground nests measure anywhere from 1.5 to 3 feet in diameter and 4 to 17 inches high; tree nests are more likely to be wider than ground nests, but are less deep. It’s hard to keep cormorants from robbing their nesting materials from your unguarded nest.

Double crested Cormorant diet and foraging

The Double crested cormorant mainly feeds on fishes and prefers ones that are bottom-dwelling, since they like to be closer to the surface of the water. They will dive up to 20 meters below the surface for their food.

As an occasional diet addition, these birds will also feed on crustaceans, other invertebrates, amphibians, and reptiles. They have been observed catching crawfish by sticking their head into the mud at the edge of a stream or pond and blowing bubbles, which causes them to rise to the surface. They then capture them with their bill and swallow them whole.

Sounds and vocal behavior

Since the double crested cormorant is an aquatic bird, it relies heavily on its senses of sight and hearing. The most intriguing vocal behavior is their ability to imitate sounds from other species of birds.

This instinctive behavior may come in handy when fighting off predators or warning nearby conspecifics that danger lurks nearby. It also comes in handy for courtship displays during the breeding season. It’s hypothesized that this imitation behavior could be part of their adaptation to life in water since they don’t have feathers on their legs for instance.

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Breeding

double crested cormorant

Double crested cormorant mate for life and congregate in colonies of up to three thousand pairs. The male finds and secures a nest site, then advertises for a female by standing in a wing-waving display that shows off the brightly-colored skin on his head and neck.

As an example, when cormorant couples pair up, they present their nest material to the female, sometimes while they’re on the water. Then they no longer have crests.

They defend a small, one-meter radius around the nest, not a large area.
During breeding season, double-crested cormorants begin nesting from April through August. Male birds arrive at the nesting colony first and choose a breeding site for their young.

As part of their mate search, they find one another and advertise to attract a partner. They collaborate on repairing or building old nests.

Typically, cormorant nests are made from sticks, twigs, and plant matter found nearby.
In addition to rope, nets, buoys, and deflated balloons, the male often brings the other materials to the female, who builds the nest. Furthermore, the female will keep the nest from competitors that try to steal the nest materials. In general, nests are found on the ground but occasionally built in trees.

In order to complete the nest, the female lays 3 to 7 pale blueish-white eggs covered in a chalky coating starting one to three days after the nest is completed. During incubation, the eggs are laid 25 to 28 days apart, and after hatching, the young are altricial, meaning both parents care for them. They each feed the chicks regurgitated food.

As soon as they can fly, at about 6 weeks old, they can no longer be carried and as soon as they can dive, at about 7 weeks old, they are ready to make the nest on their own. By the time they are 10 weeks old, they can be entirely independent of their parents. Double-crested cormorants typically don’t start breeding until they are at least two years old.

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As a result, both parents incubate the eggs and take care of the altricial chicks. The parents feed the chicks regurgitated food two to six times per day. In the warm weather, parents do their job of cooling the babies off by retrieving water and pouring it directly from their beaks into the open mouths of the chicks.

Lifespan

Double crested cormorants can live up to 22 years, but they live, on average, for 6 years.
Movements and migration

Diseases and threats

Double crested cormorants are currently threatened by habitat loss and a fungus that is killing off the Great Barrier Reef. The major concern for double crested cormorants, like many other birds, is that their eggs are becoming increasingly difficult to find because of the disappearance of nesting sites.

Population status

Some resources online presumed that there are an estimated 1,100,000 to 2,200,000 Double crested cormorants in the wild, and the continental population is approximately 740,000 breeding birds. Presently, double-crested cormorants are classified as Least Concern (LC) on the IUCN Red List and their numbers are on the rise.

Conservation and management

In the United States, this species is protected under the Migratory Bird Treaty Act of 1918. From 1986 to 2010, double-crested cormorants were assessed as a species of least concern on the IUCN Red List of Threatened Species.

However, in 2011 they were uplisted to near threatened due to an increase in population and the expansion of their range into Europe. The breeding colonies are mostly found along coastlines with high tidal ranges where there are large numbers of aquatic invertebrates that can be captured by diving birds and their young.