Cormorant Diet and Size: Feeding Habits, Predators, and Measurements

The Cormorant (Phalacrocorax carbo) is a large, striking waterbird that plays an important role in aquatic ecosystems. Known for their distinctive behaviour of spreading their wings to dry, Cormorants are a common sight along the UK’s coastlines, rivers, and lakes. 

In this article, we’ll learn more about their diet, size, breeding habits, and conservation status, providing key insights into this remarkable bird species.

The Dietary Habits Of The Cormorant

Cormorants are skilled hunters with highly specialised feeding techniques that have evolved over many years.

What Does A Cormorant Eat?

Cormorants are primarily piscivorous, which means fish make up the majority of their diet. They feed on a wide variety of fish species depending on what is available in their habitat. 

In coastal areas, Cormorants often hunt for small schooling fish like herring, mackerel, and sardines. In inland waters, they target species like perch, trout, and eels. They are particularly adept at catching fish that reside near the surface or in mid-water, though they are capable of diving to impressive depths of up to 45 metres.

Their feeding method involves diving underwater, using their webbed feet to propel themselves and their long, hooked bills to snatch fish. A unique feature of the Cormorant is that their feathers are not fully waterproof. This allows them to move swiftly through the water by reducing buoyancy, enabling them to dive deeper and more efficiently than many other birds.

In areas where fish stocks are low, Cormorants may also feed on crustaceans, amphibians, or other small aquatic animals. However, fish remains their primary source of food. In some inland locations, Cormorants have been observed preying on fish raised in fisheries, leading to occasional conflicts with humans.

What To Feed A Baby Cormorant? 

Cormorant chicks are fed by their parents through regurgitation. Adult birds catch fish, which they partially digest before feeding to their young. This regurgitated food is rich in protein and essential nutrients that the chicks need for growth and development. 

Baby Cormorants rely entirely on their parents for food during the first few weeks of life, and both the male and female share the responsibility of feeding them.

Breeding Habits Of Cormorants

The breeding season for Cormorants typically occurs between March and May in the UK, marking a busy period in their annual cycle.

Do Cormorants Mate For Life?

While Cormorants are typically monogamous for a single breeding season, they do not mate for life. Each season, they may choose a new partner, although bonds may be extended for several seasons. 

During courtship, males perform elaborate displays, including wing flapping and vocalisations, to attract a female. Once paired, both the male and female participate in building a large nest made of twigs, seaweed, and grass. These nests are usually located in colonies on cliffs or trees near water, providing safety from ground predators.

Cormorants lay 3 to 4 eggs per clutch, and both parents share incubation duties. After the eggs hatch, the chicks are fed by both parents until they are ready to fledge. It typically takes around 45 to 55 days for Cormorant chicks to fledge, although they may remain dependent on their parents for food even after leaving the nest.

The Size & Weight Of Cormorants

Cormorants are among the largest waterbirds commonly found in the UK, with a distinctive build that allows them to dive and catch fish with great efficiency.

How Much Does A Cormorant Weigh?

Adult Cormorants typically weigh between 2.1 to 2.5 kilograms. This weight helps them maintain balance during dives and resurface after catching fish. 

The Cormorant’s weight also contributes to their slower, more deliberate flight compared to lighter waterbirds. Despite being relatively heavy, they are powerful fliers, often seen flying in a straight line or V-formation with strong, deliberate wingbeats.

How Big Is A Cormorant?

Cormorants are large birds, measuring between 80 and 100 centimetres in length. Their wingspan ranges from 130 to 160 centimetres, making them one of the largest seabirds in the UK. This impressive wingspan is crucial for maintaining balance and control during flight, especially when migrating or travelling long distances in search of food.

Their long neck and slightly hooked bill give them a somewhat prehistoric appearance, and their black feathers often have a slight greenish or bronze sheen when viewed in sunlight. Juvenile Cormorants are brown with white underparts, but they gradually acquire their darker adult plumage as they mature.

Are Cormorants Under Threat?

Cormorants are currently listed as Green on the UK Birds of Conservation Concern list, indicating they are not considered at immediate risk. 

Globally, they are classified as Least Concern on the IUCN Red List of Threatened Species.

What Eats A Cormorant?

Cormorants, particularly their eggs and chicks, are preyed upon by large birds of prey such as eagles and hawks. 

Gulls, crows, and other predatory birds may also steal eggs or attack nestlings. On the ground, mammals like foxes pose a threat to nests located in low-lying areas or on islands. 

Adult Cormorants have fewer natural predators due to their size, but they are occasionally targeted by large raptors.

Where Can I See Cormorants In The UK?

Cormorants are widespread across the UK and can be seen in a variety of habitats. Coastal areas such as Norfolk, Suffolk, and Cornwall are excellent places to spot Cormorants, particularly along rocky shores where they often perch to dry their wings. They are also commonly found inland, especially around large lakes, reservoirs, and rivers.

During the winter months, Cormorant numbers increase as birds from northern Europe migrate to the UK. They can be observed along the River Thames, the lakes of the Lake District, and even in urban areas where water bodies are present.

SEE ALSO: Cormorant Life Cycle: Nest Building To Fledging (and everything in between)

Frequently Asked Questions