Food
Mainly fish. Also invertebrates, including insects, molluscs and termites, the eggs of herons and cormorants, and dead fish and refuse obtained by scavenging.
Grey-headed Gull (Chroicocephalus cirrocephalus) [XC398619]
by Ricardo Jos\u00e9 Mitidieri from Lake Nakuru National Park, Kenya (call)
Grey-headed Gull (Chroicocephalus cirrocephalus) [XC224834]
by Bram Piot from Laguna Paraiso, Lima, Peru (call)
Nest
Varies from a shallow scrape to a well built cup of rushes and grasses, on bare ground, in clumps of reeds and papyrus on islands, or on floating vegetation, often camouflaged in tall, thick vegetation.
Subspecies
Morphometric analysis links it with Silver Gull (Larus novaehollandiae) and Andean Gull (Larus serranus).
The following 2 subspecies are recognised:
cirrocephalus Vieillot, 1818 - Coastal Ecuador and Peru; coastal central Brazil to Argentina (southern Buenos Aires), and up Paraguay and Paraná basins inland to Santa Fé (Laguna de Melincué).
poiocephalus (Swainson, 1837) - Coasts and inland rivers of western Africa; widely scattered localities from Ethiopia to Malawi and southern Africa, including Rift Valley lakes (Naivasha, Manyara, Elmenteita, Nakuru, Turkana).