Appearance
A small gull, best recognised in all plumages by the wedge-shaped white markings on the primary wing feathers on the leading edges of their wings, broadening towards the wingtip. In summer plumage adults have dark brown heads (may appear black).
Size
Length 35–39 cm, wingspan 86–99 cm, weight 205–340 g.
Nest
On a mound of vegetation or floating in a lake or sea bay, also sometimes on rocky or bare ground on small islands. Nest made of the stems of aquatic plants, though may also consist of a simple depression with no nest material used.
Breeding
Usually 1–3 eggs laid from late April, incubated by both parents for 21–23 days. Fledglings learn to fly within about 24–35 days.
Distribution
Breeds almost throughout Finland, though gaps in Lapland where population is sparser. Thrives in wetland vegetation around lakes and sea bays, also on small rocky islands. May feed in urban areas and on farmland far from nest. Often nests in large colonies. Total Finnish breeding population estimated at ca. 100,000 pairs.
Migration
Leaves Finland in early autumn; nesting colonies may be abandoned in late July or early August. Small numbers winter in Finland, but most birds overwinter in Denmark or further west and south in continental Europe, and some even fly as far as Africa. Returning migrants arrive from March onwards.
Diet
Omnivorous. Invertebrates (especially worms), fish. Also forages on rubbish dumps and around street markets and harbours.
Calls
Varied shrieking and laughing calls. Colonies may be extremely noisy.
Endangerment
Vulnerable, protected in Finland. Globally Least concern.

Black-headed Gulls are smaller and slimmer than Common Gulls, and have more tapering wings. In their summer plumage adults have dark brown heads. In their winter plumage a small dark patch behind each eye is all that remains of their dark summer hoods. On birds in all plumages useful distinguishing features include their primary wing feathers, which have white colouring on the leading edge and dark colouring on the trailing edge above. Their underwings are black only near their wingtip (compared to totally black on Little Gulls). Juvenile Black-headed Gulls have grey and brown patterning on their upper parts, and white tails with a black band on the tail tip.

Black-headed Gulls’ legs are red (adults) or pinkish (juveniles). Their beaks are red with a black tip. Their eyes have brown irises and are surrounded by white eye-rings.

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