Shifts in elevational distributions of montane birds in a temperate,
arid ecosystem
Abstract
Montane species are generally predicted to respond to climate change via
upslope movement. In birds, these potential elevational range shifts
have primarily been examined in tropical regions. Although desert bird
species may be at the edge of their aridity tolerances, elevational
range shifts of desert bird species rarely have been studied. Here, we
examine shifts in the elevational distributions of breeding birds from
two regions of the Great Basin, a desert in the western United States,
over 10 to 20 years. We collected data annually from 2001-2020, a
relatively long time series that is uncommon in research on
distributional shifts. We used single-species occupancy models of 32
bird species to examine elevational shifts at three extents: the full
elevational gradient (1650-3200 m) and the lowest and highest edges
(25%) of the gradient. We then conducted simulations to test whether
population stochasticity could confound inferences about shifts. We
examined whether temperature, precipitation, and primary productivity
(normalized difference vegetation index) were associated with occupancy
and shifts. The elevational distributions of 19 species shifted, and
simulations indicated that shifts in the distributions of 12 species
were unlikely to be stochastic. The three shifts along the full
elevational gradient were downslope, and the majority of distributional
shifts occurred at the elevational range edges. Occupancy of 10 species
with elevational distributions that shifted was associated significantly
with precipitation, and 8 of those associations were negative. Although
we found that climate changed considerably even over the short temporal
extent of our study, our results suggested that this community of desert
birds is relatively resilient to the direct effects of climate change.