Check out one of the latest articles by Science News regarding birds and our climate changes…
Climate has become warmer and wetter in parts of the Sierra Nevada mountains over the past century, and the vast majority of the birds there have shifted their range accordingly, a new study suggests.
Over many generations, some plant and animal species can adapt to a slowly changing climate. When climate changes suddenly and dramatically, however, creatures generally shift their range, moving to new areas that offer suitable conditions, says Morgan Tingley, an ecologist at the University of California, Berkeley. Most previous studies have focused on species’ responses only to temperature changes. But the new study by Tingley and his colleagues — reported online and in an upcoming Proceedings of the National Academy of Sciences — shows that birds respond to changes in precipitation as well.
The researchers tallied all the species of perching birds present during breeding season at 82 sites along four transects, which stretch from low foothill elevations up to Sierra peaks topping out at more than 3,600 meters (12,000 feet). Then, they compared the results of their field studies, conducted from 2003 through 2008, with results of similar surveys at the same sites conducted from 1911 through 1929. In the intervening decades, the average temperature at the sites has risen by about 0.8 degrees Celsius and average annual precipitation has risen almost 6 millimeters, says Tingley.
In general, each species was present only in a rather narrow band of elevation — a sign that the creatures were adapted to a specific range of environmental conditions. Of the 53 species that were common at several sites both in the early 1900s and today, 90 percent had moved to a new breeding range during that time, says Tingley.
While most of those species had shifted to follow only one environmental factor — either increased temperature or increased rainfall — about 16 percent had shifted their range according to both. Birds that breed at low elevations tended to follow the rainfall, moving to wetter areas, while those that breed at higher mountain elevations tended to shift their ranges to follow the temperature most suitable for them, the researchers note. “That segregation in behavior surprised us,” says Tingley. The researchers speculate that this pattern may occur because some species, particularly those in lowland areas, are more constrained by food availability than they are by temperature.
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