February 10, 2009
Global Warming Pushing Birds Further North
Many birds in North America are moving further north and inland during the winter, providing further evidence of global warming's affect on natural systems, the Audubon Society said Tuesday.
Nearly 60 percent of the 305 species found in North America have shifted their ranges northward by an average of 35 miles, according to the report.Audubon scientists analyzed information from 40 years of Christmas Bird Count data to conclude that global warming is having a serious impact on natural systems.
The purple finch was the most noteworthy mover, as it has now shifted its winter range to near the latitude of Milwaukee, Wis., rather than its previous region of Springfield, Mo.
"As temperatures have increased in recent years, however, (purple finches) have not gone as far south during their irruptions - resulting in overall northward movement of over 400 miles in the last 40 years," said the Audubon.
Although birds can change their migrating patterns for various reasons, researchers say the only explanation for why so many birds over such a broad area are wintering in more northern locales is global warming.
Average temperatures in the US in January have increased by about 5 degrees Fahrenheit - most noticeably in the northern states - over the past 40 years.
More than half of the waterbird species "“ 52 percent "“ moved north, including a wide variety of ducks, such as Red-breasted Merganser, American Black Duck, and Green-winged Teal.
"This is as close as science at this scale gets to proof," said Greg Butcher, the lead scientist on the study and the director of bird conservation at the Audubon Society. "It is not what each of these individual birds did. It is the wide diversity of birds that suggests it has something to do with temperature, rather than ecology."
Other studies in Great Britain have come to similar conclusions, but the Audubon study covers a broader area and includes many more species.
For instance, the Carolina wren - the state bird of South Carolina "“ can now be seen in New England during the winter, according to the report.
"Twenty years ago, I remember people driving hours to see the one Carolina wren in the state," Jeff Wells, an ornithologist based in southern Maine, told the AP. "Now, every year I get two or three just in my area," he said.
"Obviously, things have changed."
On the Net:
- Audubon Society
- What the Birds are Telling Us
- The Birdwatcher's Guide to Global Warming
- Ornithological Societies of North America