Desert songbirds increasingly at risk of dehydration

Desert songbirds, especially the little fit-in-your-hand ones, could soon face widening danger zones for lethal thirst in the southwestern United States, a new study predicts.

Coping with heat waves can demand so much water evaporation to prevent heat stroke — from panting, for instance — that birds can die from dehydration, says Blair Wolf of the University of New Mexico in Albuquerque.

Small species like the lesser goldfinch (Spinus psaltria) dehydrate at a proportionately higher rate than larger birds such as towhees. If temperatures rise 4 degrees Celsius by the end of the century, a lesser goldfinch could face a risk of death within five hours on as many as 120 days a year in the worst hot spots, Blair and colleagues report February 13 in Proceedings of the National Academy of Sciences. Four other larger bird species studied, including cactus wrens and curve-billed thrashers, probably won’t see as many risky days as the goldfinch, but there’s dangerous thirst ahead for them, too.

Hot spots

For the lesser goldfinch, danger zones in its range — where heat waves could cause lethal dehydration in hours — are expected to grow under a business-as-usual climate change scenario in which local temperatures rise 4 degrees Celsius by the end of the century. As colors change from blue to red, the number of days per year (between April 1 and September 30) increases when the small songbird risks death within five hours.