The University Record, April 12, 1999

Winter songbirds may be indicators of global warming effects

By Diane Swanbrow
News and Information Services
Illustration by Patricia Duque

Like canaries in mine shafts, winter songbirds may serve as early environmental indicators of global warming, according to a U-M study that shows a link between temperatures in the Great Plains over the last 30 years and the abundance of several common species of winter songbirds.

The study was conducted by Chad Laurent, a sophomore at the School of Natural Resources and Environment (SNRE), as part of the University's Undergraduate Research Opportunity Program, and has been selected for presentation April 14 on Capitol Hill in Washington, D.C.

Working with post-doctoral fellow Russ Butler and Terry J. Root, associate professor of natural resources and of biology, Laurent correlated winter temperatures from 1960 to 1990 with the abundance of winter songbirds, as established by the annual Christmas Bird Count conducted by the National Audubon Society.

Laurent examined the abundance patterns of 14 songbird species-including the black-capped chickadee, the horned lark, the white-breasted nuthatch, the American goldfinch, the American tree sparrow and the dark-eyed junco-in four Great Plains states-North Dakota, South Dakota, Nebraska and Kansas. "We used the area of the Great Plains for the study because the topography and land cover are similar throughout the region," notes Laurent.

While all of the bird species studied spend the winter in the area, previous research by Root had shown that some species of wintering birds are associated primarily with vegetation while others are associated mainly with temperatures. Laurent's study refines and extends this work, correlating low, medium and high abundances of temperature-linked species with average winter temperatures over several different periods of time, from one to five, 10 and 30 years.

"One year's winter temperatures alone don't seem to affect the abundance of certain species," Laurent notes. "But when you look at average temperatures for three years, you can begin to see the correlation. Birds who track temperature move very quickly in response to temperature variations."

Examining population shifts in these temperature-sensitive songbird species will enable relatively short-term detection of the ecological consequences of climate change, according to Laurent. "Since watching and feeding winter songbirds is such a popular pastime in this country," he notes, "elucidating the effects that global warming has on bird abundances has tremendous potential to increase public awareness of the problem."

Helping increase public understanding of the possible changes to nature that global warming may cause, according to Laurent and Root, may in turn encourage a change in human behaviors, such as the use of fossil fuels, that may help reduce the extent of the problem.