Slender-billed gull (Larus genei)

French: Goéland railleur
GenusLarus (1)
SizeLength: 42 - 44 cm (2)
Wingspan: 102 - 110 cm (2)
Weight220 - 350 g (2)

The slender-billed gull is classified as Least Concern (LC) on the IUCN Red List (1).

The slender-billed gull (Larus genei) is most easily identified by its distinctive profile, with a long, sloping forehead and a long, slightly drooping beak, for which it is named (2) (3). The head, neck, rump and tail are white, while the back and the upper surfaces of the wings are grey, with a white leading edge to the wings and black tips to the outer primary feathers. The underparts are white, sometimes with a rosy tinge (2) (3). The slender-billed gull has long, blackish-red legs, a dark red beak, and yellowish-white eyes, with a red eye ring (2) (3). Outside the breeding season, the slender-billed gull sometimes has a small, dusky spot on the side of the head (2) (3).

The juvenile slender-billed gull has greyish markings on its head, and immature birds have darker markings on the wings and more pink-orange legs than the adults (2). This species can sometimes be confused with the black-headed gull (Larus ridibundus), but is distinguished by its more angular, sloping head, longer bill, white rather than black head during the breeding season, and slightly larger size (2) (3). The calls of the slender-billed gull include high, chattering notes and a nasal ‘yep, yep’ (3).

The slender-billed gull breeds at widely scattered, isolated locations, from Senegal and Mauritania and the south and east of the Iberian Peninsula, through the Mediterranean, Black Sea and Middle East, and into Asia, as far as Kazakhstan, Afghanistan, Pakistan and northwest India (2) (4). Only some populations migrate, with birds from central Asia generally moving south to the Arabian Peninsula and into the Horn of Africa for the winter. Some slender-billed gulls also winter at the Caspian and Black Seas and around the Mediterranean (2) (4), and the species is sometimes recorded outside of its normal range, for example in other parts of Europe (3) (4).

This species breeds on the coast around the Mediterranean Sea, Black Sea, Caspian Sea and Arabian Gulf, as well as on inland seas, steppe lakes (inland lakes which do not drain into the ocean), and on beaches, islands and sand-spits in shallow, tidal water (2) (3) (4). The slender-billed gull also uses meadows, grasslands and freshwater or brackish marshes near river deltas during the breeding season. In winter, this gull is almost always found on the coast, generally using shallow, inshore waters and salt pans (2) (4).

The slender-billed gull feeds mainly on fish, although it also takes insects and marine invertebrates, such as crustaceans, and also eats some plant material (2) (4). Food may be taken by dipping to the water’s surface, upending while on the water, plunge-diving, or by probing in mud with the beak. This species has also been known to take flying insects in the air, and will sometimes scavenge food, although less often than most other gulls (2). The slender-billed gull is a gregarious species, often seen in large flocks throughout the year (4).

Migratory populations of the slender-billed gull return to the breeding colonies around late February to March (2) (4), although immature birds may remain in the wintering grounds during the breeding season (4). Breeding usually takes place between March and May (2) (5), in large colonies which may number thousands of pairs and sometimes include other species such as terns (2). The nests are closely packed, and are usually a scrape or shallow depression on open mud, or occasionally in vegetation (2) (4), sometimes with some plant material, feathers and other objects added (5). The slender-billed gull lays 2 to 3 eggs (2) (5) (6), which hatch after around 22 days (2). The chicks of this species gather into crèches, and are led towards the sea by the adults, although the chicks are not able to fly until around 30 to 37 days old (2). The slender-billed gull first breeds at 2 to 3 years old, and has been known to live for up to 23 years (2).

The population of the slender-billed gull appears to be increasing, and this widespread species is not currently considered globally threatened (4). However, it may face a number of localised threats, including egg collection, habitat loss to tourism development, and pollution in the form of oil, plastic waste and agricultural chemicals (2) (4) (7). Human disturbance at breeding colonies can also be a problem and can lead to birds deserting the colony (6), or to increased predation of eggs and chicks by yellow-legged gulls (Larus cachinnans) and Mediterranean gulls (Larus melanocephalus) (2) (4). Storms or cold weather often also reduce breeding success by flooding nests or causing the death of chicks (2) (4), and the slender-billed gull may also be susceptible to potential future outbreaks of avian influenza (4).

The slender-billed gull is listed on Appendix II of the Convention on Migratory Species (CMS or Bonn Convention), which aims to protect migratory species throughout their range (8), and is also on Appendix II of the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA), which calls on parties to undertake conservation actions for birds which rely on wetlands for at least part of their annual cycle (9). In some areas where the slender-billed gull occurs, such as the Po Delta in Italy and the Black Sea Biosphere Reserve, Ukraine, a number of conservation activities are underway or recommended to help protect breeding colonies of gulls and terns. These include protection from human disturbance, habitat maintenance and the creation of new nesting sites, efforts to control the yellow-legged gull population to reduce predation on other species, and preventing polluted water from entering vital areas of habitat (4) (7).

To find out more about the slender-billed gull and its conservation, see:

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  1. IUCN Red List (November, 2010)
  2. del Hoyo, J., Elliott, A. and Sargatal, J. (1996) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.
  3. Peterson, R.T., Mountfort, G. and Hollom, P.A.D. (1993) Collins Field Guide: Birds of Britain and Europe. HarperCollins Publishers, London.
  4. BirdLife International (November, 2010)
  5. Dies, J.I. and Dies, B. (2000) Breeding parameters of the slender-billed gull Larus genei in a new colony located at l’Albufera de Valencia (E Spain). Ardeola, 47(2): 255-258.
  6. Oro, D. (2002) Breeding biology and population dynamics of slender-billed gulls at the Ebro Delta (northwestern Mediterranean). Waterbirds, 25(1): 67-77.
  7. Rudenko, A.G. (1996) Present status of gulls and terns nesting in the Black Sea Biosphere Reserve. Colonial Waterbirds, 19: 41-45.
  8. Convention on the Conservation of Migratory Species of Wild Animals (November, 2010)
  9. Agreement on the Conservation of African-Eurasian Migratory Waterbirds (November, 2010)