Bonaparte's Gull

识别特征

Bonaparte's gull is among the smallest of the gull species; only little gull and Saunders's gull are smaller. Adults range from 28 to 38 cm (11 to 15 in) in length, with a wingspan of 76–84 cm (30–33 in) and a body mass of 180–225 g (6.3–7.9 oz). There is no difference in plumage or bare part colour between the sexes, though males tend to be heavier than females. Bonaparte's gull is smaller-bodied, smaller-headed, and smaller-billed than the other common hooded gulls of North America. The adult has grey upperparts and white underparts; its wingtips are black above and pale below. In breeding plumage, it has a slaty black hood, which it loses in non-breeding plumage. Its short, thin bill is black, and its legs are orangish-red.<p>First year Bonaparte's gulls have the same plumage in winter and summer, but the summer plumage is paler due to wear. Fewer than 5 percent of Bonaparte's gulls acquire a dark hood in their first summer, and on those that do, the hood is duller than on breeding adults.

分类信息

When George Ord first described Bonaparte's gull in 1815, he gave it the scientific name Sterna philadelphia, assigning it to the genus now used for medium-sized terns. Most later taxonomists assigned it to the genus Larus, a longtime catch-all for most of the gull species. However, in 1858, George Newbold Lawrence moved the species to the genus Chroicocephalus, and some taxonomists followed suit. Recent molecular DNA studies have shown that this species fits neatly into a clade with other "masked gulls", and that it and the slender-billed gull are each other's closest relatives and are basal to the rest of that grouping. Based on these studies, the American Ornithologists' Union, which had previously assigned the species to the genus Larus, moved it into its current genus in 2008. It is monotypic across its range.<p>The species is named for Charles Lucien Bonaparte, a French ornithologist (and nephew to the former French emperor Napoleon Bonaparte) who spent eight years in America, contributing to the understanding of the taxonomy and nomenclature of birds there and elsewhere. Its genus name, Chroicocephalus, is a combination of the Greek words chroikos, an adjective form of chroa meaning "colour", and kephalē meaning "head". This refers to the dark heads that gulls of this genus show during the breeding season. The specific epithet philadelphia is a Latinized adjective meaning "from Philadelphia", a reference to the location from which the type specimen was collected.

学名

Chroicocephalus philadelphia

命名信息

(Ord, 1815)

目

Charadriiformes

科

Laridae

属

Chroicocephalus

分布与栖息地

Bonaparte's gull breeds in boreal forest across southern Alaska and much of interior western Canada, as far east as central Quebec and south to within 320 km (200 mi) of the United States/Canada border. It avoids dense stands of conifers, instead choosing more open areas, such as the treed edges of bogs, fens, marshes, ponds, or islands. It typically nests within 60 m (200 ft) of open water. It winters along the coasts of North America, and in the Great Lakes. It is a rare vagrant to western Europe and the Azores, where it generally associates with black-headed gulls.It is also an occasional non-breeding vagrant to the Hawaiian Islands. In 2017 a breeding pair was spotted on Iceland.

繁殖区

NA : boreal forest zone from sw Alaska mainland and nw, sw Canada to e Quebec (se Canada)

非繁殖区

e North Pacific coast to wc Mexico; inland se US; w North Atlantic coast and offshore Gulf Stream to Florida, the Bahamas and Cuba

迁徙

Complete migrants

行为

Migration pattern: Complete migrants.

保护状况

Population trend: rising.

种群趋势

rising