Use of exotic saltcedar (Tamarix chinensis) by birds in arid riparian systems

摘要: Avian use of saltcedar (Tamarix chinensis) along the middle Pecos River was compared with similarly collected data lower Colorado and Rio Grande. Use ranked high among all bird groups in seasons on River. In contrast, many species do not occur River, while few winter Occurrence granivores insectivores during may be explained by seed-producing shrubs annuals within or adjacent to these habitats. Most breeding birds are summer visitors. These species, though present, despite abundant food resources intermediate abundances Densities several summer-visiting have declined markedly since proliferation saltcedar, whereas they remained relatively stable other river valleys east. Biogeographical considerations, specifically elevational (climatic) gradients, suggested reasons for this phenomenon.