Appearance
Medium-sized gulls with black backs in adult plumage. Smaller and more slender than the Herring Gull, with longer and more sharply pointed wings. Legs yellow.
Size
Length 48–56 cm, wingspan 117–134 cm, weight 640–930 g.
Nest
Similar to nest of Herring Gull but often more carelessly constructed. Made of dry plant material. May be built in open site or among vegetation.
Breeding
2–3 eggs typically laid in May. Incubated by both parents for 25–28 days. Fledglings learn to fly within 35–40 days.
Occurrence
Nests in coastal areas and islands, also in inland waters. The members of this species that breed in Finland represent 50% of the total global population of their subspecies (ssp. fuscus). They have declined steeply in recent decades and their total Finnish population today is thought to number 6,000–8,000 pairs.
Migration
Migrates over long distances, wintering in East Africa and the Indian Ocean. Many young birds stay in their southerly wintering areas for their first summer. In autumn most birds leave fairly early during the period August–October. They return in April– May.
Diet
Omnivorous, but fish make up the most important part of their diet.
Calls
A deep “klao”, and a rapid cackling call.
Endangerment
Endangered, protected throughout the country, including the Åland Islands.

The black colouring on the backs and upper wings of adults and the extensive black tips to their underwings distinguish Lesser Black-backed Gulls from all other gull species except the Greater Black-backed Gull. Their wings are more slender and tapering than those of Greater Black-backed Gulls, the white edging to the trailing edge of their wings is narrower, and the white spot on each wingtip is only very small. Adult Lesser Black-backed Gulls have bright yellow legs (Greater Black-backed Gulls have pinkish legs). Juveniles generally have dark and light patterning like young gulls of other species, but they can be distinguished by the uniform dark colouring on their primary wing feathers. Their legs are flesh-coloured.

2- and 3-year-old Lesser Black-backed Gulls typically remain in their wintering areas in tropical Africa, and are only rarely seen in Finland. Mature Lesser Black-backed Gulls have yellow bills with a red spot near the tip of the lower mandible, and yellow irises. Juveniles have black bills and dark brown irises.

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Taxonomi

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