The black-headed gull (Chroicocephalus ridibundus) is a small, nimble gull with a wingspan ranging from 94 to 110 cm and a body length of 37 to 44 cm. It weighs between 190 and 400 grams. Despite its name, the adult's summer plumage features a chocolate-brown head, which can appear black from a distance. The body is pale grey, and the primary wing feathers are tipped with black. The bill and legs are a striking red. In winter, the brown head is replaced by a white one with dark spots. Juveniles are mottled with brown spots and have a black band on the tail. There is no sexual dimorphism in plumage.
This species nests in colonies on the ground in large reed beds, marshes, or islands within lakes. It is not pelagic and is seldom seen far from coasts.
The black-headed gull breeds across much of the Palearctic, including Europe and coastal eastern Canada. It is migratory, wintering further south, but some remain in the milder westernmost areas of Europe. It is also present in northeastern North America and occasionally seen as far south as Virginia and some Caribbean islands.
The Black-headed gull (Chroicocephalus ridibundus) is a small and one of the most abundant gulls in much of Europe and Asia, and also in eastern Canada. It displays a variety of compelling behaviors and adaptations. Some of these include removing eggshells from one's nest after hatching, begging co-ordination between siblings, differences between sexes, conspecific brood parasitism, and extra-pair paternity.
The summer adult has a chocolate-brown head (not black, although does look black from a distance), a pale grey body, black tips to the primary wing feathers, and a red bill and legs. The hood is lost in winter, leaving just two dark spots. Immature birds have a mottled pattern of brown spots over most of the body and a black band on the tail. There is no difference in plumage between the sexes. In flight, the white leading edge to the wing is a good field mark. First-year birds have a black terminal tail band, more dark areas in the wings, and, in summer, a less fully developed dark hood.
Black-headed gulls breed in much of Europe, Asia, and in coastal eastern Canada. Most of their populations are migratory and winter further south, but some birds reside in the milder westernmost areas of Europe. Some Black-headed gulls also spend the winter in northeastern North America. They breed in large reed beds or marshes, or on islands in lakes, rivers, lagoons, deltas, and estuaries. They may also occur in ponds, canals, and flood lands, nesting on the heather moors, sand dunes, or beaches. During the winter these birds are found in estuaries with sandy or muddy beaches, ploughed fields, moist grasslands, reservoirs, urban parks, farmland, and gardens.
