Great Cormorant

Exhibit of the Month 9 / 2024
Great Cormorant (Phalacrocorax carbo)

The Great Cormorant is an unmistakable waterbird from the order Pelecaniformes. It occurs on most continents. At first glance, it attracts attention with its size and behavior. It is nearly as large as a goose, adult birds are black, and during the breeding season, they have white throats, crests at the back of the head

and spots on the sides. Juvenile individuals are brown, with a light, spotted underside. Its long, strong beak with a hooked tip and legs, all four toes of which are connected by webbing, make the cormorant a perfect aquatic hunter. Its diet consists almost exclusively of fish. It is very gluttonous, capable of diving to considerable depths in pursuit of prey, and can hold its breath for more than a minute underwater. Cormorants often hunt collectively, which further increases their hunting success. Caught fish can be up to 50 cm long, but are usually around 20 cm, and are always swallowed headfirst. Due to its dietary needs, it is considered a significant pest in fish farming, and is very unpopular with fishermen, who often pursue it.

In the Czech Republic, the Great Cormorant first nested in 1982 at Nové Mlýny, and since then it has spread to many other locations. Here, it is a nesting, migratory, and wintering species. Cormorants begin nesting in March, usually several pairs together, often building nests in colonies of other waterbirds, such as herons. The nest is constructed from thicker branches, with the nesting cup made of finer twigs, grass, reeds, etc. The female usually lays 2 – 4 eggs in April, which both parents incubate for 28 – 30 days. The chicks spend four weeks in the nest. After that, they spread out into the surroundings, where the adults feed them for about another month until they learn to hunt and fly.

High numbers of cormorants can be observed every winter at Lake Most. They are usually not very shy, often drying their outstretched wings on floating docks near the shore after hunting.

Text: Jaroslav Bažant

Photo: Miloslav Anderle