Climate Change: Birds Most Influenced by Precipitation, not Warming Temperatures

Although it would seem that warming temperatures associated with climate change would most greatly influence animal species like birds, a new study shows that precipitation is actually the key to bird adaptation.

Past studies have shown that warming temperatures can push some animal species - including birds - into higher latitudes or higher elevations. However, few have explored the role that precipitation has on how they adapt to their environment.

"When we think of climate change, we automatically think warmer temperatures," Matthew Betts, an Oregon State University ecologist, said in a statement. "But our analysis found that for many species, it is precipitation that most affects the long-term survival of many bird species."

Over a period of 32 years, researchers looked at 132 bird species, examining their distribution and population numbers in parts of the United States and Canada. They took into account factors including possible changes during the wettest month in each region, the breeding season of different species and the driest month by area.

Their findings found that models that include precipitation were most successful at predicting bird population trends.

"It makes sense when you think about it," Betts added. "Changes in precipitation can affect plant growth, soil moisture, water storage and insect abundance and distributions."

The model can predict 80 percent variation for some species, while for others it's more like 50-50, but the bottom line, researchers say, is that it shows precipitation is an important factor.

Some of the variables considered in this study may have affected the accuracy of the model. For instance, the researchers chose December precipitation as one variable in this study and found it to be influential in affecting bird populations.

"Someone might ask why December, since half of the bird species usually present in the Pacific Northwest, for instance, might not even be here since they're migratory," Betts noted. "But much of the critical precipitation is snow that falls in the winter and has a carryover effect for months later - and the runoff is what affects stream flows, plant growth and insect abundance well down the road."

The next step in their research is to determine whether or not precipitation affects different species - like migratory versus non-migratory birds - in different ways.

Their findings were published in the journal Global Change Biology.