Cormorant, White-breasted cormorant, Great black cormorant, Black cormorant (Australia), Large cormorant (India), Black shag (New Zealand)
The Great cormorant is a beautiful bird with an almost primitive appearance. Its long neck giving it an almost reptilian look. It is often seen in a pose holding its wings out to dry. This bird is a supreme fisher, and this ability may be used in the Far East to man’s advantage or considered as competition in several other countries where these cormorants are persecuted.
Great cormorants occur throughout Europe, Asia, Australia, Africa and northeastern coastal North America. They frequent open marine environments and inland waters. They inhabit sandy or rocky sheltered coasts and estuaries and are rarely seen any distance from the coast. This species breeds on cliffs and inshore islands, among boulders and man-made structures. Birds that nest inland will breed on trees, in bushes, and reedbeds, and even on bare ground.
Great cormorants are active during the day and are social birds, usually leaving roosts to forage early in the morning and returning within an hour. Little time each day is spent foraging, although parents with young tend to forage for longer. Much of the day is spent resting and preening near foraging areas or at roosts. Great cormorants generally are not aggressive towards one another, apart from at nest sites, where they exhibit territorial behavior. There may be dominance hierarchies. Outside of the breeding season, these birds gather in mixed-age, mixed-sex groups. During the breeding season, individuals who are non-breeding may be present near nesting colonies. These cormorants may be both resident and migratory. Throughout the year in some areas, large groups remain within the breeding range. It is unclear whether movements are migratory or seasonal dispersals outside of the breeding area.
Great cormorants are carnivores (piscivores); they mainly eat numerous kinds of fish, and when fishing in freshwater, will also eat crustaceans, amphibians, and insects.
Great cormorants are monogamous, with pairs sometimes reuniting in subsequent years, 11% of pairs staying together for several years during one study. The male chooses the nest site, displaying to attract the female by waving his wings up and down and flashing his white rump patch. He will also swing his head from side to side while holding his tail erect and calling loudly. The female responds by swinging her head slightly and “purring”. This species breeds at any time, depending on food resources. Breeding takes place in colonies of as many as 2,000 pairs, although colonies of a smaller size are typical. Colonies are often located close to other species, like darters, herons, and spoonbills. The parents build their nest with reeds, sticks, and seaweeds on a cliff, in a tree, or in a bush, according to the region. Often a nest is reused. 2 to 6 eggs are laid, with an average of 3-4. The parents share the incubation for 27 to 31 days. The altricial chicks hatch at intervals and fledge at about 50 days old. They remain with their parents for 50 or more days, relying on them for food. The young start to breed between 2 and 4 years old, typically when 3 years old.
Great cormorants have large populations and are widespread, although surveys are not complete across their range. Being an important fish competitor, in the past, they were almost extinct in Europe. However, in recent years increases have been observed, thanks to intensive protection. But in some countries, expanding conflicts with fish farms and fisheries lead to new persecution. Another threat is that hatchlings may be eaten by raptors before fledging.
The IUCN Red List reports that the global population of Great cormorants is about 1,400,000-2,100,000, while national population estimates are: more than 1,000 wintering birds in China; in Korea, 100-10,000 breeding pairs plus more than 1,000 wintering birds; 10,000-100,000 breeding pairs in Japan, with more than 10,000 wintering birds and about 10,000-100,000 breeding pairs in Russia, with 1,000-10,000 birds on migration. Overall, currently, Great cormorants are classified as Least Concern (LC) on the IUCN Red List and their numbers today are increasing.
