Great cormorant
The Great Cormorant, the largest member of the cormorant family, is a widespread bird found across five continents. Measuring between 27.5 to 40 inches in length and weighing 92 to 130 ounces, these birds are easily identified by their dark black plumage and impressive wingspan of 47.5 to 63 inches. Well adapted to aquatic environments, they inhabit shallow coastal waters, lakes, and rivers, employing their powerful webbed feet for efficient swimming and diving to catch a variety of prey, including fish, crabs, and, in some areas, frogs or ducklings. Notably, the Great Cormorant has a unique fishing partnership with Asian fishermen, who train them to catch fish while preventing them from swallowing their catch using rings around their necks.
These birds typically nest in small colonies, sometimes expanding to over 2,000 pairs, and select locations such as cliffs or tree tops for their nests, which are made of seaweed and sticks. The female lays three to five eggs, and both parents share incubation duties, with chicks hatching after about a month. While some populations migrate, others remain stationary year-round. The lifespan of a Great Cormorant can be up to 22 years, though most live around 15 years. Their social behavior often includes solitary living, except during migration when they may form flocks.
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Great cormorant
The great cormorant is the largest member of the cormorant family and the most widespread of the species, living on five continents. It is known to catch fish for itself and Asian fishermen.
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Suliformes (Pelecaniformes)
Family: Phalacrocoracidae
Genus: Phalacrocorax
Species: Carbo
As the largest species in the cormorant family, the great cormorant is 27 1/2 to 40 inches (70 to 102 centimeters) long and weighs 92 to 130 ounces (2 1/2 to 3 3/4 kilograms). Dark black plumage covers their bodies and wings, which span 47 1/2 to 63 inches (121 to 160 centimeters).
These birds are well-suited to watery environments. They live in the shallow waters along marine shorelines but may inhabit lakes and rivers. Broad tails serve as rudders to steer their long, slender, sleek bodies as they glide easily underwater. Their webbed feet are powerful for propelling them forward in search of fish. Sharp, hooked, downward-curving bills catch prey firmly with their jagged, knife-like edges. They eat crabs, cod, flatfish, whiting, wrasse, and sand eels. Some catch frogs, ducklings, or water rats in certain areas. The cormorants' feathers are not waterproof and absorb water quickly, helping the birds stay underwater as they dive and search for food for up to one minute. The birds spread their wings to dry when they leave the water after diving. Spreading their wings also helps warm the birds after cold dives or cool them when their body temperatures are too high. Popular perching spots for drying their wings include rock reefs, sea walls, trees, buoys, and boats.
Great cormorants are known for their fishing abilities and have served Asian fishermen for centuries. The fishermen place rings around the birds' necks and release them on long leashes from boats. The cormorants dive and catch fish, but because of the rings, they cannot swallow the fish. The fishermen pull the birds back to the boat and retrieve the fish from the birds' bills. The birds receive their reward later when the fishermen remove the rings and feed the cormorants fish.
Some populations of great cormorants migrate thousands of miles, while others stay in the same places year-round. They usually live alone but form flocks when migrating.
Nesting colonies of great cormorants are generally small but may expand to include 2,000 mating pairs. They nest inland or on the coasts and select cliffs, reedbeds, trees, or bare ground. Nests are mounds of dried seaweed and sticks, typically three feet (one meter) across. The female lays three to five eggs, which the male and female incubate. One month after being laid, the chicks hatch from their pale blue or green shells and begin eating regurgitated food their parents provide. After two months, they fly from the nest but still receive food from their parents until they are three to four months old. The ability to mate comes at age four or five.
The oldest known great cormorant lived 22 years, though most live a maximum of 15 years.
Bibliography
Dewey, Tanya. "Phalacrocorax Carbo." Animal Diversity Web, animaldiversity.org/accounts/Phalacrocorax‗carbo. Accessed 20 Mar. 2024.
"Great Cormorant." Birds of the World, The Cornell Lab of Ornithology, www.allaboutbirds.org/guide/Great‗Cormorant/overview. Accessed 20 Mar. 2024.