Community science data provides evidence for upward elevational range shifts by Eastern Himalayan birds

The ongoing climate crisis is a significant threat to global biodiversity.
As Earth warms, many species respond by shifting their geographical ranges
either polewards, or in mountainous regions, upslope towards higher
elevations, presumably to track suitable thermal environments. Upslope
range shifts are of particular concern in tropical mountain ranges
because: (a) tropical species are particularly thermally sensitive, (b)
species moving upwards could become locally extirpated as they run out of
habitable space, and (c) tropical mountains harbor a high fraction of
Earth’s terrestrial biodiversity. Rapid upslope shifts can therefore
result in significant biodiversity losses. We used community science data
over a 13-year period to evaluate whether 93 Eastern Himalayan bird
species might be shifting to higher elevations. To do this, we analyzed
changes in their occurrence probabilities in eBird checklists from
birdwatching hotspots at fixed elevations. We found patterns consistent
with upslope range shifts; species with elevational ranges primarily below
hotspot elevations show increases in their occurrence probability over
time, and those with most of their elevational ranges above a hotspot
elevation decline in occurrence probability. Our findings are suggestive
of rapid responses to climate change by Eastern Himalayan birds. We
caution that Eastern Himalayan bird species might be at special risk from
increasing global temperatures because of heightened thermal sensitivity
coupled with high rates of warming in the region. To remain resilient in
the face of climate change, Eastern Himalayan birds likely require
undisturbed habitats spanning entire elevational gradients, to track
rising temperatures by moving to higher elevations.