Double-Crested Cormorant

## Description

The double-crested cormorant (Nannopterum auritum ) is a member of the cormorant family of water birds. Its habitat is near rivers and lakes 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. 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 the use of DDT, the numbers of this bird have increased markedly in recent years.

## Appearance

The Double-crested cormorant is a gangly, solid prehistoric-looking, heavy boned fishing bird of matte-black with yellow-orange skin on its face. Looking like a mix of a loon and a goose, it is a relative of the frigate bird and the booby and is commonly seen near fresh and salt water throughout North America, perhaps most visible when standing on docks, rocky islands, or channel markers, drying its outspread wings. These birds are skilled in diving for small fish.

## Distribution

Double-crested cormorants occur widely across North America, breeding locally along all coasts as well as extensively in Florida, in the center of the continent, and along the St. Lawrence Seaway, the Great Lakes and in Mexico, the Bahamas, Belize and Cuba. Cormorants usually winter along the coast of the Pacific Ocean from Alaska to Mexico, and along the Atlantic and the Gulf coasts from Belize to North Carolina, as well as inland in ice-free areas along lakes and large rivers. They inhabit a range of marine and aquatic inland habitats. They need water for feeding and perches nearby, such as rocks, sandbars, trees, pilings, shipwrecks, wires, or docks where they can rest and dry out during the day.

## Behavior

Double-crested cormorants are diurnal birds. They are very gregarious and can be found in large and small groups at the breeding grounds, and in winter, often feeding in large flocks. They breed in colonies and migrate in large groups. This species feeds during the day, diving for fish for 30–70 seconds, as deep as 1.5–7.5 m (4 ft 11 in–24 ft 7 in). After diving, the birds stand with their wings outstretched for a long time for them to dry, as they are not waterproofed fully. Double-crested cormorants swim low down in the water, often just their head and neck showing, and dive from the water’s surface. Their feet are used to propel them along. They fly low over water, their bill tilted upward slightly, sometimes flying out from the colony in a long, single-file line. They use physical displays and calls to communicate with each other, using their limited range of calls for certain social situations, but usually being silent.

## Diet

Double-crested cormorants are carnivores (piscivores), they primarily eat fish, but also insects, crustaceans and amphibians.

## Reproduction

Double-crested cormorants are monogamous. This means that males mate with only one female and females mate with only one male. The colonies they breed in can number as many as three thousand pairs. Males choose a nest site, then advertise for a female, standing to perform a “wing-waving display” to show off the brightly-colored skin on the head and neck. A male will also engage in elaborate courtship dances, including a dance in the water where he presents a female with nest material. These birds defend a small space immediately around their nest which is smaller than one meter across. Breeding takes place from Double-crested cormorants are monogamous. This means that males mate with only one female and females mate with only one male. The colonies they breed in can number as many as three thousand pairs. Males choose a nest site, then advertise for a female, standing to perform a “wing-waving display” to show off the brightly-colored skin on the head and neck. A male will also engage in elaborate courtship dances, including a dance in the water where he presents a female with nest material. These birds defend a small space immediately around their nest which is smaller than one meter across. Breeding takes place from April to August, peaking from May through July. A pair works together to repair an old nest or to build a new one on the ground or sometimes in a tree. 1 to 7 pale bluish white chalky eggs are laid (usually 4). The parents both incubate the eggs, which will hatch one after the other within 25 to 28 days. Chicks are altricial when hatched, and both parents care for them. They begin to leave their nest at 3 to 4 weeks of age. They can fly from about 6 weeks and are able to dive when 6 to 7 weeks old. Chicks are completely independent at 10 weeks old and breed once they are 2 years old.. A pair works together to repair an old nest or to build a new one on the ground or sometimes in a tree. 1 to 7 pale bluish white chalky eggs are laid (usually 4). The parents both incubate the eggs, which will hatch one after the other within 25 to 28 days. Chicks are altricial when hatched, and both parents care for them. They begin to leave their nest at 3 to 4 weeks of age. They can fly from about 6 weeks and are able to dive when 6 to 7 weeks old. Chicks are completely independent at 10 weeks old and breed once they are 2 years old.

## Population

### Population threats

These birds are susceptible to pesticide poisoning and other contaminants, as well as to oil spills. Sometimes they are killed or injured when caught by fishhooks, trawls, gill-nets, and lobster traps. Also, they are very susceptible to disturbance while nesting. Adults leave their nest unguarded when disturbed, leaving chicks and eggs open to being eaten by gulls and further predators, and in danger of overheating in the sun.

### Population number

According to the What Bird resource, the total population size of the Double-crested cormorant is 1,100,000 to 2,200,000 individuals. According to the All About Birds resource, the continental population is more than 740,000 breeding birds. Overall, currently Double-crested cormorants are classified as Least Concern (LC) on the IUCN Red List and their numbers today are increasing.

## Fun Facts for Kids

The Double-crested cormorant’s crest is visible only on adults during the breeding season. It is white for cormorants from Alaska, but black for those in other regions.

In the breeding season, a Double-crested cormorant’s throat turns bright orange.

These birds make a bulky Dest out of sticks and other matter. They frequently collect junk, like rope, fishnet, deflated balloons, and plastic debris, and incorporate this into their nest.

Large pebbles are sometimes found in cormorant nests, the cormorants treating them as eggs.

These birds’ nests are often exposed to the direct sun. Adults will shade the chicks and bring water to them, pouring it into the chicks’ mouths from their own.

To incubate the eggs, adults hold them on their feet.

A group of cormorants is called a "flight", "gulp", "rookery", "sunning", or "swim" of cormorants, amongst other names.

## References

https://animalia.bio/double-crested-cormorant