Cormorant

In some regions, such as the Caspian Sea, black shags hunt cooperatively with pelicans. Pelicans, unable to dive, drive fish toward shallow waters, while black shags prevent them from escaping into deeper areas.
Emerging from the water, the black shag kills the fish and sharply throws it into the air to swallow it more easily.
The black shag eats 1 kilogram 640 grams of fish per day. This amount makes up a significant part of its daily diet.
The black shag has a poorly developed preen gland, so its feathers get wet, and the bird is forced to dry them for a long time in the sun and wind.
In Russia, the subspecies Phalacrocorax carbo carbo nests along the coasts of the Barents and White Seas, while Phalacrocorax carbo sienensis breeds in southern regions from the Chernozemye to Primorsky Krai.
The black shag dives without splashing and can hunt at depths up to 10 meters, chasing fish. Sometimes it dives deeper and stays underwater longer.
In captivity, black shags (Phalacrocorax carbo) display cunning and hunt anything alive that can be swallowed by them.
The black shag's (Phalacrocorax carbo) beak has backward-facing spines that help hold prey, and it is long, slender, with a sharp hook at the end.

Age

The great cormorant undergoes several stages of development, beginning with an embryo that develops inside an egg, and then transitioning to the nestling stage, which receives food from its parents for a period of 1 day to 2 months. This is followed by the juvenile stage after rapid growth, when the young bird learns to fly and hunt, lasting from 2 months to 2 years. An adult bird is capable of reproduction and remains in the adult stage from 2 to 20 years. The age of sexual maturity in the great cormorant occurs during a period of 4 months 3 weeks to 4 years 5 months. The typical lifespan of the species is from 8 to 15 years, however the maximum recorded lifespan reaches 32 years 1 month, and the theoretical – from 8 years 6 months to 24 years 11 months.

Phenotype

The young black cormorant is covered in dense dark down. After a period of rapid growth, the plumage of the young is brown without white spots. Adult black shags have a long, strong beak with a hook at the end for catching fish, and feet with four toes and a complete web between them for fast swimming. The adult’s plumage is black and glossy; during the breeding season, white patches appear on the head and hips. The species has short, powerful wings that help it paddle underwater.

Physiology

Black cormorants measure in body length from 75 centimeters to 1 meter and weigh from 1.55 to 2.3 kilograms, with a wingspan of 1.4 meters. The embryo stage has a body mass ranging from 40 to 55 grams and a body length from 6 to 7 centimeters. During the chick stage, the young have a body mass from 50 grams to 1.6 kilograms and a body length from 10 to 45 centimeters. The stage of rapid growth results in a body mass from 1.4 to 2.4 kilograms and a body length from 65 centimeters to 0.9 meters. Adult black shags weigh from 2.2 to 3.5 kilograms and measure in body length from 80 centimeters to 1 meter.

Habitat

The Great Cormorant is found at altitudes up to 800 meters above sea level and inhabits temperate mixed forests with a warm summer and an abundance of oaks, birches, and maples, as well as flooded meadows with a large amount of grass; the species prefers shallow waters near the shore where crabs live, and taiga with cold winters and coniferous trees such as spruce and pine. The habitat includes freshwater, freshwater banks and backwaters, lakes and ponds, swamps and marshes, marine environments, and coastal waters. The climate in the habitats can vary: from a cold sea with potential ice formation in winter and a mild summer, to a cool summer with a temperature of +15...+20 °C, and a very hot summer when the temperature rises above +25...+30 °C. A characteristic feature is constant humidity due to frequent rains, as well as a moderate sea with cool or warm water.

Shelter

Black cormorants live in colonies on trees, rocks, or the ground near water. The species builds or uses nests as shelters for laying eggs and raising young. Nests are constructed from twigs, grass, and seaweed.

Geography

Black cormorants are distributed across several biogeographical regions, including the Afrotropical realm, Australasia, freshwater ecosystems, the Indomalayan realm, the Nearctic realm, the Palearctic realm, and marine ecosystems. The species inhabits Celtic broadleaf forests, broadleaf forests of Western Europe, Euxino-Colchian broadleaf forests, beech forests of the English lowlands, Balkan mixed forests, and Baltic mixed forests.

Feeding

The black cormorant feeds on fish, employing a hunting strategy of active pursuit. It obtains food by diving from the surface or the shore and capturing prey with its beak underwater. The species’ diet includes fish, crustaceans, amphibians, water fleas, and aquatic invertebrates. Among the specific prey items are beetles, butterflies, flies, true flies, hemipterans, dragonflies, stoneflies, net-winged insects, amphipods, oceanic squids, and neritic squids. The daily food requirement ranges from 400 grams to 0.7 kilograms. Eagles prey on black cormorants.

Reproduction

The great cormorant nests in large colonies; the female lays eggs in a nest, and both parents incubate the clutch and feed the chicks. Embryonic development takes 1 month, the brood size is 2–4, and maturity occurs at an age of 2 to 3 years. The reproductive interval for this species is 1 year, and the female lays 2–4 eggs.