Lesser black-backed gull

Voice

Fuller and deeper than Herring Gull: a raw, barking ga-ga-ga and a wailing kyow. The long call is delivered with the head thrown far back and dominates colonies from May to July, with a short nasal alarm note when you come near a nest. On roofs in harbour towns breeding birds are the first voices of the morning.

Identification

A large gull with a slate-grey to almost black mantle, distinctly paler in the western form than in the northern one but always darker than Herring Gull. Legs bright yellow, eye pale yellow with a red orbital ring, bill yellow with a red spot on the lower mandible. Because the black wingtip merges into the dark mantle the contrast is low; there is one white mirror on the outermost primary, sometimes a smaller one on the next. In winter the head is streaked grey-brown down onto the nape. First-years are dark brown and scaly, with a black bill, a crisp tail band and dark inner primaries, where Herring Gull shows a pale window; adult plumage is reached only in the fourth year.

Confusion species

Herring Gull has a far paler grey mantle, flesh-coloured legs and, in immatures, a pale primary window. Great Black-backed Gull is much heavier, with an enormous bill, flesh-coloured legs and broad white tips to the wingtip. Yellow-legged Gull is the hardest: also yellow-legged, but with a paler, bluer mantle, a heavier head and more black in the primaries. Birds of the northern form are slimmer and blacker and generate debate along the coast every autumn.

Habitat

Breeds colonially in dunes, on sparsely vegetated islands, industrial estates and flat roofs. Feeds far out at sea behind fishing boats, on arable fields behind the plough, at landfills and along the tideline, covering tens of kilometres a day. In Spain it concentrates in winter on river deltas, reservoirs, fishing harbours and refuse tips.

Range and movements

A breeder of north-west Europe, from Iceland and Norway to Brittany and Iberia. With colonies on the Maasvlakte, the Wadden islands and in the Delta, the Netherlands holds a large share of the world population of the western form. Traditionally most birds move to Iberia and north-west Africa, where the species winters in huge numbers along the Atlantic coast, the Guadalquivir and the Mediterranean, but a growing proportion now stays in north-west Europe.

• Resident
• Breeding (summer)
• Winter
• Passage
• Migration direction
• dark = core range, pale = thinly spread

Where and when to look

In August find a beach roost or a fishing harbour where adults and immatures stand together, and compare mantle and leg colour directly with the Herring Gulls beside them; seeing them side by side rather than singly saves years of practice. Watch for colour rings while you are there: Dutch birds are ringed on a large scale, and readings from Spain and Portugal yield migration data directly. Pick a moment with the sun behind you, because mantle tone is barely assessable in backlight or under heavy cloud.

Conservation status

Not globally threatened, and in the Netherlands it has grown explosively since the 1970s to tens of thousands of breeding pairs, although growth has levelled off in recent years. Reduced fishery discards and closed landfills cut the food supply, while on the mainland foxes empty colonies and avian influenza has caused local mortality in recent years. Roof nesting is increasing and creates conflict in towns, but it also gives the species predator-free space.