Length: 37 – 44 cm
Wingspan: 102 – 110 cm
Weight: 220-350 g
Appearance: medium-sized seabird with a long thick and dark red beak, a slightly orange chest and belly and a white spot on the back of the wings.
Distinguishing characteristics: larger than the Black-headed Gull, no black hood in summer.
Flight: slower wing beats than the Black-headed Gull.
Sound: rolled « krerrr », quite low and discordant.
Ecology and habitat
Nest: breeds on islets, in lagoons or salt marshes. The nest is a depression obtained by scraping the ground and lined with feathers and pieces of vegetation.
Diet: feeds on fish (50% of the diet), insects and marine invertebrates caught alive in the mud, vegetal matter.
Behaviour at sea: gregarious in winter, both when feeding and in evening roosts; rarely seen far from land.
* This map indicates coastal nesting sites in the Mediterranean and adjacent Seas.
Distribution and movement
Breeding: in lagoons and lakes around the Mediterranean and Black Sea (with large colonies in Italy, Turkey and Ukraine), Senegal, Mauritania, south and east of the Iberian Peninsula, Asia Minor and Middle East to east Kazakhstan, Afghanistan, Pakistan and north-west India.
Wintering: some individuals remain in Mediterranean estuaries and coasts, mainly Egypt and Tunisia (especially the Gulf of Gabes). Others, coming mainly from the Black Sea and the Caspian Sea, move south to highly productive Atlantic areas (such as the coasts of the Arabian Peninsula).
Phenology: Laying: late April-June; two or three brown-spotted white eggs. Incubation: 25 days. Chick-rearing: 4-5 weeks.
Global population estimate: 280,000-345,000 individuals. The European population (35,900-57,300 pairs; 107,550-172,500 individuals) is estimated to be decreasing by nearly 25% in three generations.
Threats: pollution (industrial & military effluents).
Protection level: Barcelona Convention : Annex II; Bern Convention: Annex II; Birds Directive : Annex I; African Eurasian Waterbird Agreement; Convention on Migratory Species: Appendix II; IUCN Red List: Least Concern.
Some key references
BirdLife International. 2019. Larus genei. The IUCN Red List of Threatened Species 2019: e.T22694428A154570382.
Chokri M. A., Selmi S. 2012. Nesting phenology and breeding performance of the Slender-billed Gull Chroicocephalus genei in Sfax salina, Tunisia. Ostrich 83(1): 13-18.
Isenmann P., Goutner V. 1993. Breeding status of the Slender-billed gull (Larus genei) in the Mediterranean basin. In Aguilar JS, Monbailliu X, Paterson AM – Status and conservation of seabirds. Proceeding of the 2nd Mediterranean Seabird Symposium. SEO / Birdlife / MEDMARAVIS, Calvia, March 1989. 65-70 p.
Oro D. 2002. Breeding biology and population dynamics of slender-billed gulls at the Ebro delta (Northwestern Mediterranean). Waterbirds 25: 67-77.
Sanz-Aguilar A., Tavecchia G., Afán I., Ramírez F., Doxa A., Bertolero A., Gutiérrez-Expósito C., Forero M.G., Oro D. 2014. Living on the edge: demography of the slender-billed gull in the western mediterranean. PLoS ONE 9(3): e92674.