Great Cormorant

The great cormorant (Phalacrocorax carbo) is a large and robust bird, with a wide distribution across freshwater and coastal environments in North America, Europe, Asia, and Australasia. Adults typically measure 77 to 94 cm (30-37 in) in length and display a wingspan of 121 to 149 cm (48-59 in). This species is characterized by its dark plumage, long neck, and a distinctive hook at the end of its beak, aiding in fishing. Juveniles have a more varied plumage, including a mix of dark and white feathers. Variations in plumage can also occur regionally, and particularly the African subspecies has more white on its throat and undersides, and is often referred to as the white-breasted cormorant (Phalacrocorax carbo lucidus). This subspecies has sometimes been separated as a separate species.

Great cormorants are found in a range of aquatic habitats, from lakes and rivers to estuaries and coastal areas. They are highly adaptable and can be found both in freshwater and marine environments. Their diet mainly consists of fish, which they catch by diving underwater, using their webbed feet for propulsion. These are opportunistic birds and have been observed eating a wide variety of aquatic animals besides their typical fish prey, including eels, water snakes, and even small birds on rare occasions. This flexibility in diet ensures their survival in diverse habitats and changing environmental conditions.

Cormorants are known for their remarkable fishing technique, diving from the surface and swimming efficiently to catch prey with their hooked beaks. Some individuals have been recorded diving deeper than 30 meters. They can also stay underwater for more than a minute, although typical dives last around 20-30 seconds. Their vision is also adapted to see under water, which is crucial for hunting. The lenses in their eyes change shape when the dive, allowing them to see clearly both in air and underwater.

Unlike many other water birds, cormorants have feathers that are less waterproof, which helps them dive and stay submerged longer. However, this adaptation means they need to dry their feathers after fishing to maintain body temperature and flight efficiency. Thus, they can often be seen perching with wings spread wide, basking in the sun.

Socially, great cormorants are quite gregarious, particularly outside the breeding season when they gather in large roosts for the night. These communal gatherings help protect against predators and facilitate the sharing of information about feeding areas. During the breeding season, their social nature is evident in their large colonies, which can sometimes create significant noise and activity, as well as a strong smell due to their droppings.

Migration patterns of the great cormorant vary with their geographical location. Populations in colder regions tend to be migratory, traveling to warmer areas during the winter months. Those in more temperate regions may be sedentary or make shorter, local movements in response to changing water levels and food availability.

Breeding season varies by location but generally occurs in spring. Great cormorants are colonial nesters, with colonies sometimes comprising hundreds of nests. They construct their nests out of sticks in trees, on cliffs, or on the ground on islands in lakes and rivers. A typical clutch contains 3 to 4 eggs, which are incubated for about 28 to 31 days. The young fledge after about 50 days but remain dependent on their parents for a period afterward.

The great cormorant is classified as least concern by the IUCN Red List, and has a stable to possibly increasing global population. While they face some threats from habitat loss and persecution (due to their perceived competition with fishermen), their broad range and large population size have helped maintain their status. Conservation efforts and legal protections have been effective in some areas at safeguarding their populations.