Precipitation and Not Warming Temperatures May be More to Blame for Bird Population Shifts

Warming temperatures may not impact birds as much as you might think. Instead, precipitation is what might cause problems for species in North America.

Past studies have shown that temperatures can push some animals, including birds, into higher latitudes and higher elevations in order to avoid the warmer temperatures. Yet few studies have taken a look at the role that precipitation might have. That's why researchers created new models in order to investigate its role a bit further.

The scientists examined long-term data on bird distributions and abundance covering five states in the western United States and in the Canadian province of British Columbia. They then incorporated this data into statistical models to predict temporal changes in population of 132 bird species over a 32-year period. More specifically, they analyzed the impacts of temperature and precipitation on bird distributions at the beginning of the study period and then tested how well the predictions performed against actual population trends.

"When we think of climate change, we automatically think warmer temperatures," said Matthew Betts, one of the researchers, in a news release. "But our analysis found that for many species, it is precipitation that most affects the long-term survival of many bird species. It makes sense when you think about it. Changes in precipitation can affect plant growth, soil moisture, water storage and insect abundance and distributions."

The researchers actually met with varying results. For some species, the model could predict about 80 percent of variation, but for other species it was the opposite. Yet what the findings do show is that precipitation does have an important role to play.

"In general, our study suggests that if climate change results in winters with less precipitation, we likely will see a spring drying effect," said Betts. "This means that populations of drought-tolerant species will expand and birds that rely heavily on moisture should decline."