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Increased drought drives avian community declines in the warm deserts of the United States

van den Bosch, Merijn1

Published Jul 24, 2025 on Dryad. https://doi.org/10.5061/dryad.866t1g229

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Jul 24, 2025 version files 2.64 MB

Abstract

The frequencies, intensities, and durations of extreme weather are increasing under climate change, furthering biodiversity loss. In the Southwestern USA, rising drought frequencies and intensities are anticipated to increasingly affect wildlife and their habitat. Particularly in highly arid regions, where species live closer to the limit of physiological tolerances, increasing drought emerges as a major threat to biodiversity. Using North American Breeding Bird Survey data (1998–2022) in combination with the Standardized Precipitation-Evaporation Index (SPEI), we estimated the effects of short-term (3-month), annual (12-month), and prolonged (36-month) drought on avian abundance and species richness in the warm deserts of the USA. We assessed community-level drought effects using six Bayesian relative abundance and species richness models. Our results indicate declines in avian community abundance and richness under multiple drought durations, with the strongest effects associated with annual droughts. Our models estimated that in years where annual drought met the threshold of ‘severe’, 9 out of 38 species would have 18–34% declines in relative abundance compared to a year with long-term average conditions, and species richness would decline by 10%. Availability of open water slightly mitigated negative drought effects on the avian community. Our results suggest drought will increasingly contribute to the collapse of aridland avian communities through declines in habitat generalists and obligate aridland species. Beyond mitigating future climate change, developing local adaptation strategies in arid regions, such as the conservation of water sources, appears necessary for biodiversity conservation.