Patterns of species composition and endemism in the Northern Neotropics: a case for conservation of montane avifaunas.

A review of the composition of five montane avifaunas in northwestern South America and southern Central America confirmed the distinctness of these communities from adjacent lowland areas. Excluding species that depend on aquatic resources, 1,800 bird species from 52 families were classified according to principal life zones in this review. There were 1,366 species associated with lowland areas, whereas 877 species occurred in montane areas (i.e., generally above 1,200 or 1,500 m elevation). Nearly one-half of these montane species are restricted to these high elevations, with the greatest diversity found within subtropical zones, followed by temperate and páramo zones, respectively. Comparisons with lowland avifaunas revealed that montane communities differed in trophic structure as well as familial composition. Specifically, montane communities had proportionately more nectarivores than expected by chance. When compared to randomly generated montane communities, nearly 30% of the families differed significantly in number of species from that expected if these communities were randomly assembled; eight families were more species-rich and seven families less species-rich in montane areas than expected. Moreover, montane areas had a greater number and percentage of species with restricted ranges than did lowland areas. Overall, 217 montane species (24.7%) had small geographic ranges; 142 of these were restricted to one of the five montane regions reviewed here. As evidence of the endangerment of these montane communities, nearly 10% (82) of the species are listed as threatened or near-threatened. Montane habitats are under extreme pressure from human activities. Most urban centers are located in or close to the mountains in the regions reviewed here. Given the high diversity and singularity of these avifaunas, together with high levels of habitat alteration, protection of montane ecosystems should become a priority for conservation efforts in the Neotropics.