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Sunday, October 25, 2009
Warming A Danger To Birds in Desert
By John Fleck
Copyright © 2009 Albuquerque Journal
Journal Staff Writer
Biologist Blair Wolf and his research assistant typically drank five gallons of ice water between them every two days while they sat in the Arizona desert watching birds.
That is nothing compared to the verdins, the little desert birds the scientists were studying. To cool their bodies against the 110 degree-plus summer heat, the verdins sit still in any bit of shade they can find and pant at a rate of 200 times per minute.
In the process, they lose about as much as they consume a day: a teaspoon of water. That doesn't sound like much until you consider how small the birds are. Pound for pound, it's the equivalent of a human losing 13 gallons a day.
"That's a lot of water," Wolf said.
The smaller a desert creature, the more water loss matters, and little birds like verdin are especially vulnerable, Wolf said. Sometimes, that teaspoon is not enough. On the hottest days, small desert birds can lose 5 percent of their body weight an hour to evaporation in a desperate struggle to cool off. If they cannot keep up, they die.
That rarely happens, but new research by Wolf, a University of New Mexico biology professor, suggests heat waves because of global warming will make survival far more difficult for desert birds.
Wolf and Andrew McKechnie of the University of Pretoria in South Africa took data on the birds' response to heat and calculated what would happen to them in 2080, when temperatures are forecast to be substantially hotter with heat waves 6 to 9 degrees Fahrenheit hotter, the scientists wrote in a paper published last month in the scientific journal Biology Letters.
A temperature increase that large would more than double the small birds' water loss, McKechnie and Wolf concluded, causing frequent catastrophic bird die-offs. That could upset the delicate desert ecosystems, of which the birds are a key part.
"A relatively modest increase in temperature can have a profound effect on an animal's ability to survive," Wolf said in an interview.
The work is the result of Wolf's longstanding interest in the strategies creatures employ to survive in the world's hottest deserts. Deserts make up a fifth of the world's land areas, and the creatures that live there have evolved techniques to survive the arduous conditions presented by the peak of daytime summer heat.
The verdin, a bird that typically weighs less than a third of an ounce, for example, hunts insects in the cool of morning and evening, and sits still during the heat of the day, using shade whenever it can.
The technique is not that different from the approach used by people who live in the same environment, noted James Workman, an author and expert on desert water use by human societies.
For on-the-go 21st century Westerners, the techniques described in Workman's book "The Heart of Dryness," about the bushmen of the Kalahari desert in Africa, might seem odd.
"If you're not in motion," Workman said of the Western approach to living, "you're wasting your time."
But like Wolf's desert birds, Workman notes, the bushmen have become extraordinarily adept at sitting still during the heat of the day and doing absolutely nothing.
They keep their mouths closed to avoid evaporation in their breath. Their only movement, Workman said in an interview, comes as they shift with the angle of the sun to stay in whatever bit of shade is available.
Wolf said his research, funded by the U.S. government's National Science Foundation, is an example of the benefits of basic science. When he started the work in the 1990s, the notion that it would be important for understanding the effects of climate change was not an issue.
"Basic research like this is important because it often reveals unexpected relationships," he said, "in this case showing that what might appear to be a modest increase in environmental temperature can have profound effect."
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