干旱区生态环境知识资源中心

We examined the relationship of breeding birds to elevation across and within four adjacent mountain ranges in the central Great Basin, a cold desert in western North America. Data came from 7 years of point counts at elevations from 1,915 to 3,145 m. We focused on eight passerine species that in this region are associated frequently with Pinus monophylla-Juniperus spp. (pinyon-juniper) woodland. Mean elevation of species’ presence differed significantly among mountain ranges for all species except Spizella passerina (Chipping Sparrow); all species except Spizella breweri (Brewer’s Sparrow) occurred at the highest mean elevation in the Toquima Range. Observed patterns were consistent with the elevational distribution of pinyon-juniper woodlands that provide nesting and foraging habitat for these species. Across the Great Basin, driven in part by climate change, pinyon-juniper woodland is increasing in density and expanding its distribution at lower elevations. However, breeding habitat for species dependent on mature trees may not be available in expansion woodlands for several decades, and increased tree densities may have negative effects on bird species that are dependent on shrubs within open pinyon-juniper woodlands. Responses of individual species to elevation differed from the response of assemblage-level patterns. Responses to biotic and abiotic variables within guilds of birds are sufficiently diverse, and responses of individual species sufficiently heterogeneous, that one management strategy is unlikely to meet the needs of all species in the group.