Black-chinned sparrow

Appearance

The black-chinned sparrow is a small passerine, measuring 5 to 5+3⁄4 in. in length, with a wingspan of roughly 7+3⁄4 in.. It weighs 0.3–0.5 oz, with a median weight of 0.4 oz. Overall, it is a slender, round-headed bird, with a high crown and a long, notched tail, which is proportionately longer than that of other "Spizella" sparrows. The sexes are similar, though the male averages slightly larger. The adult's head and body are gray, and its back is reddish-brown with black streaks. It has a "poorly defined" whitish belly, and its rump and uppertail coverts are an unstreaked gray. The feathers in its wings and tail are dark brown with paler edges. In alternate plumage, the male has extensive black on its chin, throat and the front of its face. It loses most or all of this black during the nonbreeding season; the oldest males may retain some black flecking. The female has little or no black on her face, chin, or throat at any point during the year. In basic plumage, males and females can be difficult to tell apart. The juvenile resembles a nonbreeding adult, but shows indistinct streaking on its underparts, and two faint wingbars. The head and underparts have a brownish wash, and its outer scapulars are tawny-colored. The legs and feet are dark brown or dusky, and the bill is small, stout, and pink. Recent fledglings may have darker bills, as well as notably short tails, yellow gapes, and paler gray heads.

Distribution

The black-chinned sparrow breeds in the southwestern United States and throughout much of Mexico north of the Isthmus of Tehuantepec. It is regularly found from northern California east to western Texas, and as far north as southern Nevada and Utah, and has occurred as a vagrant or occasional breeder in Oregon and Colorado.

Behavior

Although the black-chinned sparrow appears to be relatively common where it occurs, it is an inconspicuous species that can be easy to overlook. In Mexico, it is generally found singly or in pairs, and only rarely in small groups. In the United States, it is sometimes found in small, loose groups, occasionally mingling with Brewer's or chipping sparrows. It flies close to the ground, with an undulating flight style. Though the species often remains in deep cover, breeding males defy that more typical behavior and pick conspicuous, exposed perches from which to sing.

Habitat

A species of arid and semi-arid places, it lives in chaparral, sagebrush, pine-juniper woodlands, and other brushy shrubland. Much of its habitat is in remote, rugged, and rocky areas. It is significantly less common in edge habitat, and rare near the coast. It is found at elevations ranging from near sea level to 2,400 m in the United States, and from 300 to 2,500 m in Mexico. Some birds in Utah may move into desert ecotones as part of a post-breeding dispersal and some northern populations move into Chihuahuan Desert scrub during the winter. Most northern populations move south – primarily into Mexico – during the winter; some move to lower elevations as well. During migration, it is sometimes recorded in montane oak forest, but not in mixed pine-oak forest.

Reproduction

Much of the breeding ecology of the black-chinned sparrow is poorly known. It breeds primarily from late April into June, though active nests have been found as late as the middle of July. Males sing from open perches within their territory, which may encompass as much as 2 hectares. Neighboring males often counter-sing, alternately responding to their singing rivals. They also aggressively chase each other. The nest is a shallow, open cup built of plant material, including grasses, weed stems, rootlets, or yucca fibers. This is lined with fibers or fine grasses, and occasionally with hair or feathers. It is located within 4 ft of the ground, typically at mid-level in a dense shrub. The female does the bulk of the nest building, though the male may help. The nest is occasionally parasitized by cowbirds.

The female lays 2–5 very pale blue or bluish-green eggs. These are typically unmarked, though occasionally speckled with brown spots. Incubation takes roughly 13 days, and is done primarily by the female. The young are altricial – featherless with eyes closed upon hatching. Both parents provide food for the nestlings and remove fecal sacs for the 11–13 days it takes for the young to fledge. Adults continue to feed the fledglings for several weeks after they leave the nest. Most pairs raise a single brood per year, though there are records of a few pairs attempting multiple broods in southern California. Pairs stay together only for the length of breeding season. Nests suffer a high rate of failure; in one study in southern California, fewer than 30 percent of nesting attempts were successful. Most eggs and young are lost to predators. Garter snakes are known nest predators. Other suspected nest predators include western scrub jays, snakes, lizards, rodents, and ants.

Food

The black-chinned sparrow forages on or near the ground, spending considerable time working in the same area. Though its diet is not well-known, it appears to feed primarily on seeds as a ground-gleaning granivore in the winter, and on insects as a ground-foraging omnivore in the summer. It occasionally captures insects in flight, and may feed on seeds while perched in a bush. It appears to obtain all of the moisture it needs from its food during the summer, but in the winter may travel a considerable distance to reach a water source.