Birds' patterns changing in face of global warming

The bushy sphere is a great kiskadee nest, and it's the type of thing that lured Rappole from his position at the National Zoo in Washington to the Rob and Bessie Welder Wildlife Refuge in South Texas for two months of fieldwork.

“That is it,” said the senior research scientist. “You find that and it's a thrill.”

The great kiskadee is not supposed to be here in rural San Patricio County. Neither is the green jay or the green kingfisher or several other species of birds flying around the 7,800-acre refuge.

Rappole should know. He spent three years here as a graduate student in the early 1970s, netting birds and documenting the results.

The birds are among some 70 species in Texas that Rappole believes have shifted their range to the north and east in the past 30 years.

The big question is why. Rappole has come to the same conclusion as several other ornithologists: It must have something to do with a changing climate. The theory, Rappole admits, is based on circumstantial evidence. But, given the wide array of birds shifting ranges, he can't come up with another reasonable explanation.

“There will be a different explanation for every species for why the range is expanding,” he said. “It's only when you take them all together with their very different habitat and their very different life spans that you get the idea that something much more pervasive is going on.”

The idea that global warming is having an impact on plants and wildlife is nothing new. The polar bear has emerged as something of a poster child for the issue in the wake of reports that melting sea ice could spell extinction for the species by the end of the century.

The latest report of the Intergovernmental Panel on Climate Change concluded there is “high confidence” that rising water temperatures are causing shifts in the ranges and populations of algae, plankton and fish. It also stated a “very high confidence” that recent warming has pushed up the timing of bird migration and egg laying and caused general “poleward and upward shifts in ranges in plant and animal species.”