Defend and Grow the Core for Birds: How a Sagebrush Conservation Strategy Benefits Rangeland Birds

Abstract

Population declines among sagebrush (Artemisia spp.) reliant birds mirror the larger deterioration of the sagebrush ecosystem. To combat this biome decline, western partners have unified around a common vision for sagebrush conservation by developing the Sagebrush Conservation Design, which identified high-priority areas, designated as “core sagebrush areas” (CSAs), to anchor conservation actions throughout the biome. While this conservation design did not explicitly consider the distribution or abundance of focal species, an underlying assumption has been that sagebrush-associated wildlife will benefit from actions targeting threats to the sagebrush biome. Herein, we explicitly test whether sagebrush ecological integrity (SEI), the metric used to quantify CSAs, is associated with sagebrush songbird abundance and population trends, such that CSAs provide an effective umbrella for wildlife conservation. Because species likely vary in their response to different ecological factors, we further examined the relative importance of the five components of SEI: sagebrush cover, tree cover, perennial grass cover, annual grass cover, and human modification, in structuring sagebrush songbird populations. We found substantial increases in population counts associated with increased values of SEI across three species examined: sagebrush sparrow (Artemisiospiza nevadensis), Brewer's sparrow (Spizella breweri), and sage thrasher (Oreoscoptes montanus). Specifically, models supported 10 times (sage thrasher), six times (Brewer's sparrow), and three times (sagebrush sparrow) higher median relative abundances in CSAs compared with surrounding areas. Further, we found strong evidence of large population declines as areas transitioned out of CSAs. Finally, although we found some species-specific differences in the relative importance of the five SEI components, generally, sagebrush cover and tree cover were more important than grass cover in influencing bird populations. We show that conservation actions designed to preserve or grow CSAs will likely benefit sagebrush-obligate songbird populations and other focal wildlife, especially if consideration is given to which component(s) of SEI are targeted.