Chronic, sublethal effects of high temperatures will cause severe declines in southern African arid-zone birds during the 21st century

Significance We synthesized physiological and behavioral data to evaluate the risks of acute, lethal effects of extreme heat events versus the sublethal costs of chronic exposure to sustained hot weather for birds inhabiting southern Africa’s Kalahari Desert over the course of the 21st century. The risk of mass mortality events similar to those predicted for the American southwest and sometimes observed in Australia will remain low for Kalahari birds. However, the sublethal costs of chronic exposure, manifested as progressive loss of body condition, delayed fledging, reduced fledging size, and outright breeding failure, will likely drive major population declines. We anticipate that much of the Kalahari’s avian biodiversity will be lost by the end of the century.