Striped Sparrow is a large, bulky, and flat-headed sparrow described as Aimophila-like but with a more pointed, all black bill (Byers et al. 1995, Howell and Webb 1995). Adults of both sexes have a black face and a creamy white supercilium. The sides of the crown are chestnut with black streaks, and the median crown stripe is gray, streaked with black. The pale gray underparts become white on the throat and are washed buff on the flanks (Howell and Webb 1995). Juveniles are similar in coloration but have a much duller head pattern, less neatly marked upperparts, and spotted flanks (Howell and Webb 1995).
Striped Sparrow is superficially similar to Stripe-headed Sparrow (Peucaea ruficauda), but is readily separated from that species (including juveniles) by its all black bill and its brown crown with a less obvious median stripe (Byers et al. 1995, Howell and Webb 1995). Striped Sparrow is distinguished from Rusty Sparrow (Aimophila rufescens), Rufous-crowned Sparrow (Aimophila ruficeps), and Oaxaca Sparrow (Aimophila notosticta) by its completely white supercilium (including the postocular portion), blackish mask, and paler underparts (Howell and Webb 1995).
The following descriptions are based on Ridgway (1901), Byers et al. (1995), Howell and Webb (1995), and Rising (2011), and refer to the nominate subspecies; see also Geographic Variation.
Adult/first year: Sexes alike. The adult is a largish, flat headed sparrow, resembling Aimophila and Peucaea sparrows but with a more pointed bill that is all black. The lores and auriculars are blackish, forming a mask, but white streaks on the rear auriculars can make it appear diffuse or gray at a distance. The crown is rufous with fine black streaks and a narrow gray median stripe, and is separated from the auricular mask by a long, broad, creamy white supercilium. The nape and sides of the neck are light grayish streaked with black. The mantle and scapular feathers are buffy brown with heavy black streaks formed by the black feather centers and paler streaks formed by the pale gray feather edges. The lesser coverts are warm brown with pale gray edgings. The alula is blackish with a broad white outer edge. The primary coverts are blackish with rather broad pale buff edges. The greater and median coverts are colored like the primary coverts, but also have whitish tips which form obscure wing bars. The remiges are blackish with narrow grayish white edges to the primaries, narrow buff brown edges to the secondaries, and tertials similar to the secondaries but with the edges becoming almost whitish at the tips. The bend of the wing is white. The tail is quite long and rounded; the rectrices are dark brown with buff brown edges, with this edging broadest on the central rectrices, which also have a wavy cross-barring pattern. The outer rectrices have more contrastingly buff outer webs and tips than other rectrices. The underparts are generally pale grayish white, but are whitest at the throat and central belly. The flanks and undertail coverts are washed buffy.
Juvenile: Buffier overall than adult, with dusky dark brown streaking or flecking on the breast and flanks. Duller head pattern than adults, with upperparts less neatly marked. The juvenile also has been described as grayer than the adult, with lower throat, breast, belly, and flanks thinly streaked with black (Rising 2011).
Adults have a complete molt, most likely after the breeding season (Byers et al. 1995). Unknown are the extent of the post-juvenile molt and aging criteria after the post-juvenile molt is complete (Byers et al. 1995). A prealternate molt is probably absent (Byers et al. 1995).
The bill is all black (Byers et al. 1995, Rising 2011). The iris has been illustrated as brownish (Howell and Webb 1995). The legs are flesh colored (Byers et al. 1995, Howell and Webb 1995) or pinkish (Rising 2011).
Total length: 16.5-18 mm (Howell and Webb 1995)
Linear measurements (from Ridgway 1901; n = 10/sex):
wing length (chord), mean 78.7 mm (range 75.7-81.8 mm)
tail length, mean 70.4 mm (range 67.3-73.2 mm)
bill length (exposed culmen), mean 15.2 mm (range 13.2-15.5 mm)
tarsus length, mean 25.7 mm (range 23.4-27.9 mm)
wing length (chord), mean 76.0 mm (range 73.7-80.8 mm)
tail length, mean 67.3 mm (range 63.5-70.6 mm)
bill length (exposed culmen), mean 14.7 mm (range 13.2-15.5 mm)
tarsus length, mean 26.0 mm (range 24.9-27.4 mm)
male, mean 39.8 g (range 38.6-41.0 g, n = 2; Paynter 1952, Binford 1989)
female, mean 39.7 g (range 36.9-41.5 g, n = 5; Paynter 1952, Binford 1989)