A comparison of avian use of high- and low-elevation sites during autumn migration in central New Mexico

We compared the migratory bird assemblage at a high-elevation site in central New Mexico (Capilla Peak in the Manzano Mountains) with the bird assemblage at a low-elevation riparian corridor site (Rio Grande Nature Center State Park in Albuquerque). During fall 2001-2003, we used mist nets to sample these bird assemblages. We found greater species richness at the low-elevation site than at the high-elevation site, both overall and for most migratory and resident subgroups. However, at the high-elevation site we captured more species that may have had local origins at high elevations. Over the course of the study, capture rates were similar between sites, but there was greater annual variation in capture rates at the high-elevation site than at the low-elevation site. Several species were captured at higher rates at one site versus the other, and some were captured strictly at one or the other site. Our data showed that both sites supported many species in large numbers, and both riparian and montane habitats in the southwestern U.S.A. should be recognized for their importance as potential stopover sites for migrating birds.