Original description: Emberiza rostrata Cassin 1852
AOU 1 (1886): Large-billed Sparrow, Ammodramus rostratus
AOU 2 (1895): Large-billed Sparrow, Ammodramus rostratus
AOU 3 (1910): Large-billed Sparrow, Passerculus rostratus rostratus
AOU 4 (1931): Large-billed Sparrow, Passerculus rostratus rostratus
AOU 5 (1957): Savannah Sparrow, Passerculus sandwichensis rostratus, Passerculus sandwichensis atratus
AOU 6 (1983): Savannah Sparrow, Passerculus sandwichensis [rostratus group]
AOU 7 (1998): Savannah Sparrow, Passerculus sandwichensis [rostratus group]
IUCN Conservation Status: Of least concern
Behavior: Large-billed Sparrows are not particularly shy, but especially out on the sun-baked salicornia flats where they breed, they quite understandably prefer whatever shady cover they can find. They calmly walk and scratch beneath low salt-tolerant vegetation in search of food, running or briefly fluttering across the intervening patches of open sand or mud. Truly sustained flight is almost never seen, but disturbed birds fly off in fast, generously swooping flight, often calling on flushing and then disappearing beneath the next piece of substantial vegetation.
At a breeding site, patience and the rising tide generally result in good views of these birds. At high water, they readily perch on the tops of short plants, rocks, or low structures, and if the sky is not too bright and the temperature too high, they may emerge to feed along vehicle tracks or even on open beach.
Voice: The call notes are high, thin, and very short, like those of the other Passerculus sparrows. Males sing from a low but conspicuous perch; the song typically begins with three or four call-like ticking notes, followed by a thin, buzzing trill and ending with a clearly emphasized down-slurred buzz: tee-tee-tee-tliddl-teTEEah.
Detailed description and measurements drawn from standard reference works
Adult, subspecies rostratus: Medium-short, shallowly notched tail dull buffy gray with indistinct paler edges. Rump and upper tail coverts dull pale gray with faint, diffuse darker brown shaft streaks. Mantle and scapular feathers slightly darker, with variably broader and more conspicuous dark shaft streaks, in some individuals forming long blurry stripes down the back. Primaries pale gray, bleaching paler in worn plumage. Secondaries edged with richer brown, tertials with dark brown centers and thin whitish edges. Greater coverts dull rusty with paler brown edges and, in fresh plumage, fine whitish tips forming narrow, often incomplete lower wing bar. Median coverts brown-gray with darker centers and, in fresh plumage, whitish tips forming poorly defined wing bar. Nape pale dull buffy gray with fine darker brown streaks. Underparts off-white, with buffy wash on breast and flanks; brightest white on throat, often with fine dark brown flecks or streaks. Flanks, sides of breast, and breast with broad, poorly organized brown or dull cinnamon streaks, surrounding the nearly unmarked belly. Dull brown crown, slightly darker than nape and back, with barely a hint of a paler median stripe. Long, broad supercilium buffy white, finely streaked brown behind the eye and in some birds approaching dull yellow above lore. Broad whitish jaw stripe separated from throat by brown, often incomplete lateral throat stripe and from ear coverts by brown whisker. Ear coverts dull gray brown, bordered above by faintly contrasting brown eye line, which interrupts very narrow white eye ring. Huge pink-brown bill with dark upper ridge and often dark tip to lower mandible. Thick feet and toes brownish pink.
Juvenile: Very similar, but even less regularly patterned beneath.
Subspecies atratus is identical in pattern, but darker, with darker brown streaks above and below.
Length 137-139 mm (5.4-5.5 inches)
Wing chord 67-72 mm (2.6-2.9 inches)
Tail 51-53 mm (2.0-2.1 inches)