Water access during hot weather
Posted: 10 Feb 2011, 00:50
Here is an article that may interest people this summer
http://www.unm.edu/~market/cgi-bin/archives/004342.html
"Scientists Study Climate Change and its Role in Avian Mortality Events During Heat Waves
Climate change models, with increasing regularity, are projecting increases in the duration, frequency and intensity of heat waves over the next 70 years. How this information is going to affect plant and animal species across the globe has scientists like Blair Wolf from the University of New Mexico and Andrew McKechnie from the University of Pretoria in South Africa searching for answers.
Photo: Budgies cluster together in a shady spot to get out of the heat.
Together, they are utilizing physiological models to understand what might happen to bird communities during the extreme heat-related events that are projected to occur.
The duo, in a paper released by Biology Letters this week, say that by the 2080s, desert birds will experience reduced survival rates more frequently during mid-summer heat waves leading to an increase in the number of catastrophic mortality events. Birds with body weights of less than 100 grams, smaller than a Mourning Dove, will be most affected.
Wolf and McKechnie used climate data from Yuma, Ariz. and Birdsville, Australia, two areas well-known for their extreme temperatures, to model the effects of high temperatures on bird survival. They modeled water requirements and survival times during the hottest times of the day for birds resting in the shade and used evaporative water loss measurements for the highest current and predicted future maximum temperatures in 2080.
They also took into account important characteristics of birds such as body size, their use of thermally buffered microsites, like shade trees, limited drinking and foraging activity. Under these circumstances, they found, that small birds will be particularly vulnerable to such heat waves because their evaporative water loss rates and water requirements will be much higher in the 2080s than under current conditions.
“Their water requirements for the 2080s are much higher than current values because of projected higher temperatures,” said Wolf. “For a bird the size of a hummingbird, a 5.5°C temperature increase will result in an increase in water requirements of 95 percent over a 12 to 18 hour period in a bird that weighs three to five grams. The increase in a 50-gram bird would be about 64 percent, and 47 percent in a 500-gram bird over the same timeframe.
“Even when it’s hot out and they seek shade to stay cool, small birds can still have evaporative water loss rates that exceed five percent of their body mass per hour. As with humans, moving from a shady site into the sun on a hot day greatly increases their heat stress"
Their model is based on the assumption that water intake is negligible during the hottest part of the day and the observation that birds forego most activity when it is very hot.
During hot weather, two mechanisms are at work explains Wolf. “Birds either lose so much water that they reach a lethal dehydration limit or it is so hot that they can't get rid of enough heat to keep their body temperature below its lethal limits.
“Under normal conditions, a bird’s body temperature is around 106-107° F,” said Wolf. “When is it hot, birds allow their body temperatures to increase to 113 or 114° F and temperatures around 115 to 117° F are lethal. In the 2080s, increased air temperatures during heat waves will make it impossible for some species to maintain body temperatures below lethal limits as has recently occurred in western Australia.”
Wolf and McKechnie explain in their paper that, “historically and contemporary reports of catastrophic avian die-offs, taken together with predicted increases in frequency, intensity and duration of heat waves strongly suggest that future climates will produce more frequent mortality events. The die-offs will periodically reduce populations, potentially by millions of individuals over large areas.”
They say that although birds are highly mobile, the short time scale over which dehydration and hyperthermia occurs makes it unlikely that they will be able to escape such events, and that these events also may affect the reproductive success of some species because some birds actually cool their eggs during hot days; increased temperatures will make it impossible for some species to maintain egg temperatures below lethal levels.
“An example is the January 2009 heat wave in western Australia that has killed off thousands of birds,” said Wolf. “Australia is the poster child for global climate change; they are losing all sorts of wildlife due to its effects."
Media Contact: Steve Carr, (505) 277-1821; e-mail: [email protected]
"
http://www.unm.edu/~market/cgi-bin/archives/004342.html
"Scientists Study Climate Change and its Role in Avian Mortality Events During Heat Waves
Climate change models, with increasing regularity, are projecting increases in the duration, frequency and intensity of heat waves over the next 70 years. How this information is going to affect plant and animal species across the globe has scientists like Blair Wolf from the University of New Mexico and Andrew McKechnie from the University of Pretoria in South Africa searching for answers.
Photo: Budgies cluster together in a shady spot to get out of the heat.Together, they are utilizing physiological models to understand what might happen to bird communities during the extreme heat-related events that are projected to occur.
The duo, in a paper released by Biology Letters this week, say that by the 2080s, desert birds will experience reduced survival rates more frequently during mid-summer heat waves leading to an increase in the number of catastrophic mortality events. Birds with body weights of less than 100 grams, smaller than a Mourning Dove, will be most affected.
Wolf and McKechnie used climate data from Yuma, Ariz. and Birdsville, Australia, two areas well-known for their extreme temperatures, to model the effects of high temperatures on bird survival. They modeled water requirements and survival times during the hottest times of the day for birds resting in the shade and used evaporative water loss measurements for the highest current and predicted future maximum temperatures in 2080.
They also took into account important characteristics of birds such as body size, their use of thermally buffered microsites, like shade trees, limited drinking and foraging activity. Under these circumstances, they found, that small birds will be particularly vulnerable to such heat waves because their evaporative water loss rates and water requirements will be much higher in the 2080s than under current conditions.
“Their water requirements for the 2080s are much higher than current values because of projected higher temperatures,” said Wolf. “For a bird the size of a hummingbird, a 5.5°C temperature increase will result in an increase in water requirements of 95 percent over a 12 to 18 hour period in a bird that weighs three to five grams. The increase in a 50-gram bird would be about 64 percent, and 47 percent in a 500-gram bird over the same timeframe.
“Even when it’s hot out and they seek shade to stay cool, small birds can still have evaporative water loss rates that exceed five percent of their body mass per hour. As with humans, moving from a shady site into the sun on a hot day greatly increases their heat stress"
Their model is based on the assumption that water intake is negligible during the hottest part of the day and the observation that birds forego most activity when it is very hot.
During hot weather, two mechanisms are at work explains Wolf. “Birds either lose so much water that they reach a lethal dehydration limit or it is so hot that they can't get rid of enough heat to keep their body temperature below its lethal limits.
“Under normal conditions, a bird’s body temperature is around 106-107° F,” said Wolf. “When is it hot, birds allow their body temperatures to increase to 113 or 114° F and temperatures around 115 to 117° F are lethal. In the 2080s, increased air temperatures during heat waves will make it impossible for some species to maintain body temperatures below lethal limits as has recently occurred in western Australia.”
Wolf and McKechnie explain in their paper that, “historically and contemporary reports of catastrophic avian die-offs, taken together with predicted increases in frequency, intensity and duration of heat waves strongly suggest that future climates will produce more frequent mortality events. The die-offs will periodically reduce populations, potentially by millions of individuals over large areas.”
They say that although birds are highly mobile, the short time scale over which dehydration and hyperthermia occurs makes it unlikely that they will be able to escape such events, and that these events also may affect the reproductive success of some species because some birds actually cool their eggs during hot days; increased temperatures will make it impossible for some species to maintain egg temperatures below lethal levels.
“An example is the January 2009 heat wave in western Australia that has killed off thousands of birds,” said Wolf. “Australia is the poster child for global climate change; they are losing all sorts of wildlife due to its effects."
Media Contact: Steve Carr, (505) 277-1821; e-mail: [email protected]
"