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.
The great cormorant is currently listed as Least Concern by the IUCN. Conservation efforts have led to a population rebound, with approximately 1.2 million birds in Europe alone. However, their increasing numbers have led to conflicts with fisheries due to predation on fish stocks.
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