The Great cormorant (Phalacrocorax carbo) is a widespread member of the cormorant family of seabirds. Many fishermen see in the Great cormorant a competitor for fish. Because of this, it was hunted nearly to extinction in the past but luckily due to conservation efforts, its numbers increased.
The Great cormorant is a large black bird, but there is a wide variation in size in the species' wide range. Males are typically larger and heavier than females. It has a longish tail and yellow throat patch. Adults have white patches on the thighs and on the throat in the breeding season. In European waters, the Great cormorant can be distinguished from the Common shag by its larger size, heavier build, thicker bill, lack of a crest, and plumage without any green tinge. In eastern North America, it is similarly larger and bulkier than the Double-crested cormorant, and the latter species has more yellow on the throat and bill and lack the white thigh patches frequently seen on great cormorants.
Great cormorants occur throughout Europe, Asia, Australia, Africa, and northeastern coastal North America. They may be both resident and migratory. Throughout the year in some areas, large groups remain within the breeding range. Greta cormorants 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, bushes, and reedbeds, and even on bare ground.
Great cormorants are monogamous, with pairs sometimes reuniting in subsequent years. 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.
The great cormorant (Phalacrocorax carbo), a robust seabird, is cloaked in predominantly black plumage. It is a member of the cormorant family, with a widespread distribution. The species exhibits considerable size variation across its range, with males generally larger than females. Notable features include a longish tail and a distinctive yellow throat-patch. During the breeding season, adults boast white patches on their thighs and throat.
To identify the great cormorant, look for its large size, heavy build, and thick bill. It lacks a crest and its plumage does not have a green tinge, distinguishing it from the common shag. In North America, it is bulkier than the double-crested cormorant and has less yellow on the throat and bill. The white thigh patches are a key identifier.
Great cormorants are found in a variety of aquatic environments including seas, estuaries, freshwater lakes, and rivers. They often nest in colonies close to these water bodies.
This species has a broad distribution, breeding across the Old World, Australia, and the Atlantic coast of North America. Northern populations tend to migrate southward in winter, seeking coasts rich in fish.
Great cormorants are generally silent but may emit guttural noises at breeding colonies. They are known for their wing-drying posture, often seen with wings outstretched to dry after diving.
Mostly silent, the great cormorant vocalizes with guttural sounds in the vicinity of its breeding colonies.
Great cormorants typically nest in colonies near wetlands, rivers, or sheltered inshore waters, often returning to the same site annually. Their nests are constructed from sticks and can be located in trees, on cliff ledges, or on predator-free ground. They lay clutches of three to five pale blue or green eggs, which are incubated for about 28 to 31 days.
These birds are piscivorous, diving to catch fish such as wrasses, sand smelt, flathead, and common soles. They exhibit seasonal dietary shifts, preferring larger fish in colder temperatures. Their foraging efficiency is influenced by the size of the prey rather than the quantity.
