Avian richness, status, and conservation in the northwestern neotropics in Sonora, Mexico

We assessed the status and richness of birds in a remote region of northwest Mexico and provided the first description of a bird community in foothills thornscrub vegetation across the full annual cycle of seasons. Our efforts were part of a broad program to describe biodiversity and conservation value of the Northern Jaguar Reserve. This large private reserve was recently proposed for federal protection, in part, because it supports the northernmost breeding population of jaguars (Panthera onca) and extensive riparian woodlands along the largest free-flowing river in western Mexico. The reserve and surrounding region are dominated by foothills thornscrub, which is a vegetation community that covers a vast transition zone between tropical forest and desert-scrub in northwest Mexico but is not represented in the federal system of Natural Protected Areas. Bird species richness was similar to that found in other protected areas in western Mexico. Over seven years, we observed 214 species of birds and estimate that 241 species are present (95% CI = 225-257). Community composition was temporally dynamic; 49% of species were winter residents or passage migrants, 31% were permanent residents, and 15% were summer residents. We observed 10 species that were breeding or wintering north of the previously described limits of their geographic ranges. We observed 13 species of conservation concern in Mexico, including the Bald Eagle (Haliaeetus leucocephalus) and Military Macaw (Ara militaris) that occur at the extreme southern and northern edges of their breeding ranges, respectively. High environmental variation and unique biogeographic and physiographic settings in this region promote high bird species richness and high conservation value.