Tree-line as a break-line: habitat specialist birds increase with elevation in the temperate Andes
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Date
2018
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Abstract
Mountain ecosystems comprise 24% of the land-base of world. Avian communities have been poorly studied in southern temperate Andes. Opposite to tropical mountains, habitat specialization of birds is not expected to be a strong ecological force generating high beta diversity in temperate mountain ecosystems. During 2011-2018, we investigated patterns of avian species distribution between 220 m and 1,768 m elevation (n=750 counts) in southern temperate mountain gradients (Chile; 38-39°S latitude). Specifically, we compared: i) taxonomic and functional turnover across four habitats across elevations: lower montane forest (LM, <700 m of elevation, >50% tree cover), upper montane forest (UM, >700 m of elevation, >50% tree cover), subalpine (SA, 5-50% tree cover), and alpine (AL, <5% tree cover). We found 55 bird species (in 20 families and 10 orders) inhabiting Andean temperate mountains. Total species richness was consistent across elevations (~35 species/habitat), but species composition varied among elevational habitats. Species similarity was highest below the tree-line (LM-UM=0.97), and lowest between LM and AL habitats (0.17). The community-weighted body mass in alpine habitats was 1.9 and 2.6 times higher than both montane and subalpine habitats, respectively. Overall, we found a gradient in bird communities from predominantly habitat generalists below tree-line (habitat specialist: LM=0.0%, UM=3.4%, and SA=11.1%), where the main turnover occurs, to more habitat specialists above tree-line (87.0% of alpine bird communities). Elucidating how bird communities are distributed in southern temperate mountain ecosystems is critical for understanding the potential conservation value of mountain habitats for avian populations under an environmental change scenario.
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Ornithology, Andes, Natural Resource Ecology, Mountain Areas