It is a small gull (a little bit larger than the pigeon). In summer, its head is black-brown; the legs and beak are red.
They are very noisy birds. Their call is bitter "kyarr".
In the first autumn, young birds have brown flashes on the back; and only in the third year their heads become black-brown and legs and beak gain red coloration. Only from that time, they take part in reproduction for the first time.
The most desired places for nests of black-headed gulls are marsh hummocks surrounded by water and overgrown with sedge.
These birds, as well as all gulls, display on land. Here partners inform each other about their love with the help of ritual movements.
They form strong married pairs.
The clutch is incubated by both parents.
The young, from the second week, run around the nest and can collect food on the ground. And the parents bring them food and put it in front of them. After one week, the young go in water.
As soon as young black-headed gulls learn to fly, they leave the area of nesting.
Its body is less than the body of pigeon. Its upper part is bluish-grey; the bottom is white. Adult birds have a red beak with black tip, or all black. The legs are red. The tail is fork-shaped.
They look for food in flight, hanging in air above the water. Then they rush to water vertically downwards. So they catch little fishes, water insects, bloodsuckers.
They swim seldom and slowly; the webbings on their feet are small.
They nest on sandy and pebbly spits, on low coasts of lakes. An ideal habitat for these birds is rivers with wide valleys, pure water and sandy islands overgrown with shrubs. It is found also on seacoasts.
Formation of pairs is preceded by a courtship display with plenty of poses and gestures; pairs rise to large height; at that, the male carries a fish in the beak. It happens in other cases that a male with a fish flies to his beloved, sits down, brags of the catch, swinging it in front of her. And if the female accepts the gift — this means that the couple is formed.
The nest of the common tern on sandy ground or pebble is simply a pit. But at a bog it can be constructed as a big heap from plants. The clutch is incubated by both partners. In afternoon, they frequently replace each other; at night one of them sleeps on eggs, and another — at the edge of the nest.
Hatchlings are rather helpless in the beginning; the food given to them can drop out off their mouths, and the parents patiently give it to them again. But when the young grow up, parents simply put the food in front of them. Sometimes a kid hardly swallows a fish, which can be longer than its body, and the fish’s tail sticks out from the beak, whereas the fish’s head is already digested in the stomach.