Original description: Fringilla graminea Gmelin 1788
AOU 1 (1886): Vesper Sparrow, Poocætes gramineus; Western Vesper Sparrow, Poocætes gramineus confinis
AOU 2 (1895): Vesper Sparrow, Poocætes gramineus; Western Vesper Sparrow, Poocætes gramineus confinis; Oregon Vesper Sparrow, Poocætes gramineus affinis
AOU 3 (1910): Vesper Sparrow, Poœcetes gramineus; Western Vesper Sparrow, Poœcetes gramineus confinis; Oregon Vesper Sparrow, Poœcetes gramineus affinis
AOU 4 (1931): Eastern Vesper Sparrow, Pooecetes gramineus gramineus; Oregon Vesper Sparrow, Pooecetes gramineus affinis; Western Vesper Sparrow, Pooecetes gramineus confinis
AOU 5 (1957): Vesper Sparrow, Pooecetes gramineus gramineus, Pooecetes gramineus confinis, Pooecetes gramineus affinis
AOU 6 (1983): Vesper Sparrow, Pooecetes gramineus
AOU 7 (1998): Vesper Sparrow, Pooecetes gramineus
IUCN Conservation Status: Of least concern
Though still globally common and, in much of the west, locally abundant, the Vesper Sparrow has retreated significantly from vast portions of the eastern range it occupied during the nineteenth- and early twentieth-century peak of extensive agriculture in the northeastern United States and eastern Canada. East of the Mississippi River, populations in most areas may now have declined to levels more like those of the period before European settlement, a result of urbanization, reforestation, and, perhaps, environmental pollution. As a representative case, breeding Vesper Sparrows passed from “abundant” in Kentucky at the turn of the twentieth century to a single pair less than one hundred years later.
Breeding populations of the Vesper Sparrow are currently listed as endangered in Connecticut and New Jersey, as threatened in Massachusetts, as vulnerable in West Virginia, and of special concern in New York. The breeding subspecies in each of these jurisdictions is the nominate gramineus.
The Oregon Vesper Sparrow, Pooecetes gramineus affinis, is clearly the most immediately imperiled population of this species. It was likely never numerous in coastal British Columbia, but today, with only approximately five breeding pairs remaining on Vancouver Island, it is listed as endangered in Canada. Habitat loss, human disturbance, and predation by non-native mammals such as house cats have reduced the Washington population to some 400 birds, and the subspecies is now a candidate for listing as endangered in that state. In Oregon, the bird’s status is considered critical.
California’s breeding population of affinis, discovered in 1976, is now estimated at between ten and twenty-five pairs. Nearly all of the subspecies’ population winters in California, however, where urbanization and agricultural development threaten the habitat of this obligate grassland bird; overgrazing may also be a source of habitat degradation there.
Habitat: A summer resident of lush grasslands with scattered low shrubs and trees, the Vesper Sparrow is more catholic in its wintertime habitat choices, often found at such barren open country sites as beaches, low sagebrush and quailbush deserts, and muddy roads and lakeshores, where it feeds with back and tail held parallel to the ground and head and neck hunched forward. Though they occasionally walk, Vesper Sparrows most typically run or hop, with little of the shuffling sometimes indulged in by Savannah and other grassland sparrows.
At all seasons, Vesper Sparrows show a marked preference for drier habitats than Savannah or Song Sparrows.
Behavior: Feeding birds often allow close approach with no obvious sign of alarm, then take off suddenly with high, fairly long calls. Once flushed, Vesper Sparrows fly strongly away, generally taking a direct course with relatively little swooping; wintering birds usually land on the ground, in the open or under light cover, but migrants and breeders sometimes fly into trees, occasionally landing surprisingly high and in the open before dropping to the ground to feed or flying on.
Voice: Territorial males sing from exposed perches including fences, dried forbs, telephone wires, and bushes and trees; in flat agricultural land in the old midwest, they often use cornstalks. There is also a rarely observed flight song, in which males fly high over their breeding territory uttering a series of notes shorter than the introductory whistles of the usual perched song; those notes are followed by trills resembling the remainder of the normal song.
Detailed description and measurements drawn from standard reference works
Adult: Tail dusky gray brown, the outermost rectrix entirely white on outer vane and approximately half-white on inner; next inner rectrix with white tip and edge. Upper tail coverts and rump dull gray-brown (grayer in some subspecies, browner in others) with dark brown shaft streaks; ground color of back dull gray-brown with broader, more prominent but still blurry brownish-black shaft streaks, aligning to form ragged, low-contrast dark stripes. Primaries gray-brown with thin faintly grayer edges, secondaries more broadly edged grayish. Tertials darker sooty brown with broad brown edges. Greater coverts sooty blackish with poorly defined gray-brown edges and tips; lower wing bar irregular, incomplete, or essentially absent. Median coverts blackish with narrow paler gray V-shaped tips, in fresh plumage forming irregular, jagged upper wing bar, but quickly wearing to leave irregular blackish patch formed by coverts, conspicuous when scapulars are raised. Lesser coverts, usually concealed by scapulars, bright pale chestnut, forming triangular patch at “shoulder.” Nape on average slightly grayer than back, with fine black streaks. Undertail coverts, vent, and belly dull whitish to creamy; flanks, sides of breast, and sometimes center of breast often with yellow-buffy wash. Flanks and sides with fine brown-black shaft streaks; streaks broader, coarser, and often darker across upper breast. Breast streaks form ill-defined band, together with sparser flank streaking framing unmarked lower breast and belly. Throat whitish, occasionally with tiny black or brown flecks. Dusky streaking at sides of throat forms irregular, incomplete lateral throat stripe, bordered above by broad creamy jaw stripe, faintly flecked dark near base of bill. Jaw stripe curves sharply back along lower edge of ear coverts, isolating them from sides of nape and creating conspicuous ear surround. Crown brown to gray, finely streaked blackish; narrow, incomplete whitish median crown stripe when present continuously streaked blackish. Ear coverts plain brown-gray, with smudgy darker whisker and rear margin surrounding paler center of covert patch. Eye line obscure or absent. Grayish supercilium finely streaked black, plainest above dull gray-brown lore. Narrow but bright whitish eye ring, often slightly attenuated behind eye and usually thickest above eye. Thick bill pinkish-yellow below, pinkish-gray above with extensive gray-brown on culmen and sides. Long, sturdy tarsus dull gray-pink, less bright than in most Savannah Sparrows.
Juvenile: Buffier on rump, back, and nape than adult, but paler, colder, and grayer beneath, with less regular streaking and more diffuse gray-buff on flanks intruding onto belly.
The dimensions given here are for the large, widespread western subspecies confinis.
Length 146-149 mm (5.7-5.9 inches)
Wing chord 80-84 mm (3.1-3.3 inches)
Tail 62-66 mm (2.4-2.6 inches)
Mass 20-28 g