No abstract

Tropical species, many of which have limited thermal tolerances and narrow ecological niches, are likely to experience elevational shifts due to climate change. However, our ability to predict these shifts is limited by a scarcity of baseline data on current distributions and a lack of understanding of drivers of species ranges. To characterize the elevational distributions of a suite of Afromontane birds, we conducted annual point counts between 2013 and 2018 at 297 plots across habitats and elevations (2416–4303 m) in Volcanoes National Park, Rwanda. We assessed elevational and habitat preferences via indicator analyses, and modeled abundance distributions as a function of temperature, precipitation, habitat availability, and congeneric competition. Although most of the 35 focal species were distributed across habitats and elevational ranges, 20 species particularly associated with narrow elevational range (<300 m) and 24 species were strongly associated with one to three habitat types. Abiotic factors significantly correlated with abundance distributions of 33 species (temperature 33, precipitation 17), and biotic factors with distributions of 31 species (habitat 30, competition 7). Temperature and habitat availability were particularly associated with upper elevational limits (31 and 26 species, respectively, vs. 10 and 6 at lower limits), whereas precipitation affected both limits similarly (17 lower, 16 upper), and competition had a limited role at either limit (4 lower, 3 upper). That the elevational distribution of Afromontane birds results from a species‐specific combination of biotic and abiotic factors is crucial information in our effort to predict climate change effects in this region.

Photo 4. The Crowned Hornbill (Lophoceros alboterminatus) is a species more common in savannas at lower elevations, but is with increasing frequency observed at the forest edge of the boundaries of Volcanoes National Park in Rwanda, at elevations of >2,000 m. Evidence of range shifts? Photo credit: Yntze van der Hoek/The Dian Fossey Gorilla Fund International. These photographs illustrate the article "Living the high life: remarkable high-elevation records of birds in an East African mountain range." by Yntze van der Hoek, Faida Emmanuel, Valens Musemakweli, and Deogratias Tuyisingize published in Ecology.