How are Brewer's Sparrows Affected by the Encroachment of the Exotic Grass Species, Smooth Brome (Bromus Inermis Leyss.)?

Abstract

Sagebrush habitats (Artemisia spp.) across the western United States have been continuously altered since the arrival of early European settlers. Habitat loss and fragmentation in sagebrush-dominated habitats has been attributed to domestic livestock, introduction of non-native vegetation, agricultural expansion, urbanization, and changes in ecological processes that regulate ecosystems (Knick et al. 2003). These alterations have resulted in landscape level changes; for example, it is estimated that between 50-60% of the nearly 63 million hectares once covered by sagebrush in the west have been either completely converted to non-native grasslands or now contain non­native grasses in the understory (Miller and Eddleman 2001, West 2000 and 1996). The encroachment of non-native plants that compete with native vegetation has been identified as one of the most serious threats to the health and integrity of sagebrush ecosystems throughout the west (Paige and Ritter 1999).