July 28, 2017

Dry Heat

UMass Amherst researcher studies native songbirds at risk in a warming climate

When it’s 120 degrees in Phoenix, it’s not only planes that aren’t flying. Desert birds are also grounded—hunkered down in the shade until it cools off—but if they stay too long, they can weaken from dehydration and be unable to replenish their water. It’s a vicious cycle, one that UMass Amherst is collaborating with other universities to understand.

So given that heat waves in the Southwestern desert are growing longer, more intense, and more frequent, how will birds cope?

A new study of songbird survival risk during high-temperature episodes in the United States desert Southwest joined researchers from UMass Amherst, the University of New Mexico, and the University of Nevada, Reno, to identify the threat and which species will be most impacted.

“The uniqueness of this collaboration arises from the way it combines climate mapping and geographic information with physiological data,” says Alexander Gerson, assistant professor of biology, who contributed his expertise in how birds handle thermal stress to the study.

Using land-surface modeling and hourly temperature maps, the team projected the potential effects of current and future heat waves on lethal dehydration in birds and how rapidly this can occur in species native to the Sonoran Desert. 

Their models revealed that increasing air temperatures and heat wave occurrences will potentially affect the water balance, daily activity patterns, and geographic distribution of arid-zone birds. Some regions of the desert could become uninhabitable for many species, and future high-temperature events could depopulate whole regions—as they have with mass avian die-offs occurring in Australia and South Africa.

“The uniqueness of this collaboration arises from the way it combines climate mapping and geographic information with physiological data.”

Alexander Gerson, Assistant Professor of Biology

Die-offs would open up niches for more resilient birds, like white-winged doves—making the whole avian community—and beyond that, the overall ecosystem—subject to change. In addition, when animals alter their daily activity patterns, that impinges on their web of interrelationships.

Refugia microclimates might prove important in management plans for vulnerable species. “For instance, desert willow trees exude water, which can keep the area around them a degree or two cooler,” says Gerson. “That could be enough to make a difference, but we need more data for sure.” These climate oases can be maintained not just on public lands, but by private landowners as well.

The researchers’ next move is to study birds in tropical and temperate climates: their response to changing rainfalls in the tropics and thermal stress in a warming Arctic, where an increase of a few degrees, while it may not seem hot to us, would seem torrid to a cold-adapted bird.

All photos by Tom Kennedy, University of New Mexico