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Extreme heat threatens desert songbirds

"During heat waves, birds that are day active suspend almost all activity and seek cool shaded microsites," said biologist Blair Wolf.

By Brooks Hays
Extreme heat threatens desert songbirds
The cactus wren is one of several desert songbird species increasingly at risk of death by dehydration as heat waves become more frequent. Photo by Tom Kennedy/UNM

Feb. 14 (UPI) -- A number of songbird species make their living in some of the most precarious places on Earth -- deserts. As global warming pushes temperatures higher and extreme heat waves occur more frequently, deserts are becoming even more inhospitable.

In a new study, researchers calculated how extreme heat waves affect the risk of death by dehydration faced by five desert songbird species in the American Southwest. They published their findings in the journal PNAS.

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Scientists built a physiological songbird model to estimate how rising temperatures in the deserts of the southwestern United States would affect evaporative water loss, the primary method by which desert songbirds keep cool when temperatures spike.

"During heat waves, birds that are day active suspend almost all activity and seek cool shaded microsites," Blair Wolf, a professor of biology at the University of New Mexico, said in a news release. "At high air temperatures, the rates of evaporation needed to cool the bird increase rapidly. A 2 to 3 degrees Celsius increase in air temperature can result in a doubling or tripling of rates of evaporative water loss where birds can lose 2 to 5 percent of body mass per hour."

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"By focusing on heat waves and dehydration in birds, it allows us to focus more carefully on one piece of the puzzle," added Tom Albright, an associate professor of geography at the University of Nevada-Reno. "It allowed us to use mechanistic understanding supported by actual physical measurements of evaporation from birds' bodies."

Because smaller species lose water more quickly than larger species, they're at most risk of death by dehydration. Their risk will increase fourfold if projections of a 4-degree Celsius increase in temperature by the end of the century hold true. For some species, such an increase would render much of their current range uninhabitable.

"When combined with increasing drought projected for many of these regions, we could see precipitous declines in bird communities and increasingly severe stress on poultry as well," Wolf said.

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Researchers now hope to use their modeling data to determine which types of plants and conservation strategies will best serve desert songbird species as they try to adapt to climate change.

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