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Editor’s Note: —Based on differences in mitochondrial DNA, morphology, and ecolog, this species was recently split, with two species resulting: Bell's Sparrow (A. belli) and Sagebrush Sparrow (A. nevadensis). See the 54th Supplement of the AOU Checklist for details. Future revisions of this account will adjust for this change.
The Sage Sparrow is a widespread breeder in shrub-steppe habitats from the northern edges of the Great Basin sagebrush expanses west of the Rocky Mountains to the chaparral and sagebrush scrub in Baja California. Great Basin sage-brush habitat was the focus of intense avian-community ecology studies from the late 1970s to the early 1980s, and these studies provide the basis of what is known about the Sage Sparrow today.
Although often quite common, this inconspicuous sparrow is frequently overlooked by observers because of its habit of running on the ground from shrub to shrub. Territory sizes vary greatly among populations; some are the largest found in any sparrow species. In spring, males sing from their favorite song perches while females build nests low in shrubs or occasionally on the ground. The selection of ground for a nest substrate may be related to the height of available shrubs and microclimate. Incubation and nestling periods are relatively short, as is common for many other sparrows, and Sage Sparrows frequently raise more than 1 brood per year. Although adults are site-tenacious from year to year, both male and female young disperse in subsequent years.
Only 2 of the 5 recognized subspecies of Sage Sparrow are migratory. During fall and winter, individuals can be found foraging on the ground in small flocks or pairs, giving their characteristic bell-like tink call. Migratory subspecies are site-tenacious both in winter and during breeding. Nonmigratory subspecies begin territory defense by singing and chasing as early as mid-January.
The San Clemente Island (CA) subspecies (A. b. clementeae), a “conspicuous” element of that island’s bird population during the early 1900s, was severely affected by the introduction of pigs, goats, feral cats, rats, and other grazing animals. Since its listing as Threatened under the Endangered Species Act in 1977, actions have been taken to improve its habitat and restore the population. Other subspecies throughout the western United State mainland may be declining because of loss of habitat resulting from urbanization, suburbanization, and agricultural conversion, especially in southern California.