Passeriformes / Passerellidae / Passerculus
Savannah Sparrow
Passerculus sandwichensis · 稀树草鹀
Introduction
A small New World sparrow (Passeriformes: Passerellidae), the only member of the genus Passerculus. It is a widespread and abundant species occupying open grassland habitats throughout North America. Over most of its range it is migratory, breeding in Canada and the northern United States while wintering in Mexico and the southern United States. It is a sexually monomorphic species with considerable phenotypic variation across its range. Approximately 17 subspecies are currently recognized, some of which have occasionally been treated as separate species. The species is considered threatened by the IUCN (sensu lato).
Description
A typically sparrow-like bird with dark-streaked brown upperparts and whitish underparts featuring brown to blackish streaking on the breast and flanks. The head displays whitish crown and supercilium stripes, often with yellow coloration near the beak. The cheeks are brown and the throat is white. Flight feathers are blackish-brown with light brown to white edging. The eyes are dark, while the feet, legs, and lower mandible are horn-colored; the upper mandible is dark grey. Total length ranges from 11 to 17 cm, wingspan from 18 to 25 cm, and body mass from 15 to 29 g. The nominate subspecies averages 20.1 g. Plumage darkness varies considerably among subspecies following Gloger's rule, with Alaskan and interior races being palest and southwestern coastal forms darkest.
Identification
A variable species with numerous subspecies that can be difficult to distinguish, particularly migratory individuals which cannot usually be assigned to specific breeding populations with certainty. Resident and partially migratory subspecies are more readily identifiable by size and coloration. The species shows a general pattern where birds southwest of a biogeographic divide become notably darker. Key identification features include the combination of streaked underparts, whitish head stripes, and variable yellow coloration near the bill base. The Ipswich subspecies (P. s. princeps) is notably larger and paler with narrower, pale brown breast streaks.
Distribution & Habitat
Breeds across Alaska, Canada, the northern and central United States, the Pacific coast, Mexico, and Guatemala. Pacific and Mexican populations are resident, while other populations are migratory, wintering from the southern United States south through Central America and the Caribbean to northern South America. The species is a very rare vagrant to western Europe. Inhabits open grassland habitats, including grazed low-growth grassland.
Behavior & Ecology
Forages on the ground or in low vegetation; in winter also found in grazed grassland. Diet consists primarily of seeds, with insects added during the breeding season. Typically encountered in pairs or family groups during the breeding season, forming flocks for winter migration. The flight call is a thin seep. The song is a variable mixture of chirps and trills. Some subspecies, such as the Ipswich sparrow, may raise three broods annually.
Conservation
Listed as threatened by the IUCN (sensu lato). Population trends and specific threats are not detailed in the source material.
Culture
The common name refers to Savannah, Georgia, where Alexander Wilson first observed the species in 1811 and subsequently introduced the English name. The specific epithet sandwichensis derives from Sandwich Sound (now Prince William Sound) in southern Alaska, the collection locality of the type specimen.
Source: Wikipedia · CC BY-SA 3.0
