Introduction

One of the more widely distributed Aimophila sparrows, the Rufous-crowned Sparrow is a locally common resident of dry hillsides and canyons of the southwestern United States and Mexico. Its shy, secretive habits and predilection for inaccessible, rocky, brush-covered slopes make this species difficult to observe and study, although it has an unmistakable scolding, nasal call and males often sing from prominent perches.

For the most part, the Rufous-crowned Sparrow is a resident species. Although individuals in northern populations show slight range shifts during winter in response to severe weather, most populations apparently do not undertake regular migratory movements. Throughout its range, this sparrow is normally found on moderate to steep, dry, rocky slopes vegetated with a low cover of scattered shrubs which are interspersed with patches of grasses, forbs, and bare ground. Pairs generally nest on the ground, and most nests are carefully hidden in hollows among rocks or under clumps of grass or low bushes. Individuals seldom wander far from the protective cover of shrubs or grass, usually foraging for seeds and insects in vegetation close to the ground and in litter beneath shrubs.

In part because of this sparrow’s cryptic appearance, inconspicuous song, stealthy behavior, and remote habitat, little is known about its life history. Gaps remain in our knowledge of its reproductive and population biology, physiology, food habits, ecology, behavior, and development of young. Most published accounts of this species are anecdotal. From California and Arizona, however, some detailed information is available on evolution, systematics, geographic variation, morphology, plumages and molts, vocalizations, singing behavior, predation, and habitat characteristics (Hubbard 1975, Wolf 1977, Groschupf 1983, Wimer 1995, Ellison 1998, Collins 1999).