Species ranges and diversity patterns in tropical montane birds

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Tropical mountains have more bird species than any other region on earth. One reason for this high diversity is that bird communities change dramatically from the lowlands to mountain tops as species drop out and are replaced by others. This research has two major initiatives. First, we aim to improve our knowledge of how many species occur on tropical mountains and how diversity changes along mountainsides. Second, we will strive to understand why many species are restricted to just a portion of the elevation range available on the slopes of tropical mountains. In other words, what prevents lowland birds, which can fly long distances, from colonizing habitats only 500 meters upslope? The Manu Biosphere Reserve in the Andes of Peru and the Monteverde Cloud Forest of Costa Rica were chosen as sites for this work because they are prime biodiversity "hotspots". For example, along a 75-km transect in Manu, we can find 1100 bird species, more than in all of North America. The first initiative will rely upon surveys of species and their habitats to map diversity patterns across the landscape, with the help of satellite sensors that remotely describe habitat structure across large areas. The second initiative will determine the range of elevations that species can potentially occupy based on their tolerance of different temperatures. For species that do not occupy the entire range of conditions that are physiologically tolerable, we will study how interactions with the environment and other species, such as food resources and competitors, may instead determine where species can live. Tropical mountains have been targeted as regions where climate change will have large impacts on plants and animals. More than a quarter of the world's endangered bird species inhabit these regions. Over the next century, many tropical species will have to move upslope as temperatures increase. Anything that prevents them from colonizing new environments will increase their risk of extinction. Currently, almost nothing is known about tolerances of any tropical species to changing temperatures. Species interactions could also affect upslope movements in response to warming. This research will provide these data for many species in biodiversity hotspots.