Code from: Climate, ecological dynamics, and the seasonal distribution of birds in mountains

Biodiversity is unevenly distributed along elevational gradients. The
predominant hypothesis is that macroevolutionary dynamics and climatic
niche conservatism explain today’s elevational patterns of biodiversity,
but the alternative energy efficiency hypothesis emphasizes modern
ecological interactions related to energy budgets. We test these competing
hypotheses by examining seasonal elevational ranges for 10,998 bird
populations in 34 mountain regions. Multiple lines of evidence support the
energy efficiency hypothesis, including that many mountain birds do not
seasonally track their thermal niche with high fidelity, while simulation
models based on optimal energy balancing under current environmental
conditions yield predictions that tightly match empirical data. Our
results reveal that altitudinal migration, which is widespread yet
considerably understudied, is a behavioural mechanism fulfilling the same
ecological function as long-distance latitudinal migration. Overall, this
work provides a better understanding and predictive capacity for mountain
birds under global change.