Chroicocephalus
Genus of birds
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Through Basal (phylogenetics)
Taxonomy
The species now placed in this genus were formerly assigned to the genus Larus. A molecular phylogenetic study published in 2005 found that Larus, as then constituted, was paraphyletic. In the resulting rearrangement to create monophyletic genera, the genus Chroicocephalus was resurrected to contain a clade of species, all of which have black heads. The genus Chroicocephalus had been introduced in 1836 by the English naturalist Thomas Campbell Eyton. Although he listed two species in the new genus, he did not specify a type. In 1840 George Gray designated the type as Larus capistratus which had been described by Coenraad Jacob Temminck in 1820. This taxa is now considered to be a junior synonym of Larus ridibundus, the black-headed gull, that had been named in 1766 by Carl Linnaeus. The genus name Chroicocephalus combines the Ancient Greek χρωικος/khrōikos meaning "coloured" with -κεφαλος /-kephalos meaning "-headed".
Saunders's gull was formerly included in this genus until a 2022 study demonstrated that although it occupied a basal position in the genus, it was not closely related to the other members. It is now placed in its own genus Saundersilarus.
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Description
The species range from 28 cm up to 48 cm long, with Bonaparte's gull being the smallest, and Andean gull the largest. In all species, the body and tail are white, and the upperwing pale grey; the wingtips have distinct grey, white, and black patterns important for identification. Several have distinctively brown, pale grey, or blackish-grey coloured heads in the breeding season, but some also have the head pure white like the rest of the body. The eyes are dark in some species, or with a distinctive white iris in others; the legs and bills are bright to very dark red.
Representatives of this genus are found in regions/subregions all over the world, except for Antarctica; the species are often parapatric, but with two species together in New Zealand, the Mediterranean region, parts of southern Africa, and parts of South America. Exceptionally, three species (black-headed, brown-headed, and slender-billed gulls) can occur together in parts of southwest Asia.
Species
The genus contains ten species.
Fossils
- †Huahine gull Chroicocephalus utunui Huahine in the Society Islands, French Polynesia