By Deborah Zabarenko
Washington - Climate change is pushing American birds northward, with some finches and chickadees moving hundreds of kilometres into Canada, an Audubon Society study reported on Tuesday.
Drawing on citizen observations over a 40-year period, the society's scientists found that 58 percent of 305 widespread bird species found in the contiguous United States shifted significantly to the north.
While there are many factors that can make birds move, there's no question this is caused by human-spurred global warming, according to report co-author Greg Butcher.
"There's a thousand things that cause birds to change their range, and so if you do a study of a whole bunch of birds, you'll see some moving north, some moving south, some moving west," Butcher said in a telephone interview.
"What was real surprising about this study is to see the birds moving so uniformly in one direction," Butcher said.
Scientists were able to relate this movement with temperature changes from 1966 through 2005.
"That uniformity of movement and then a whole bunch of different tests we were able to take to correlate those movements with temperature change that make it so obvious that it's global warming is what we're dealing with here," he said.
All kinds of birds moved north, but more of the highly adaptable forest and feeder birds - upward of 70 percent - made the move, compared with only 38 percent of grassland species, the study found.
The Purple Finch, Pine Siskin and Boreal Chickadee moved deep into the Canadian Boreal Forest, shifting their ranges 504km, 396km and 340km, respectively.
Southern-dwelling water birds including the Red-breasted Merganser, Ring-necked Duck and American Black Duck shifted their ranges northward by lesser distances.
Only 10 of 26 grassland species made significant moves north. Birds including the Eastern Meadowlark, Vesper Sparrow and Burrowing Owl may have been unable to despite more moderate northern temperatures because grassland habitats have been converted to human uses such as row crops, pasture and hayfields.
There will be fewer of these grassland birds as global warming and pressure on grasslands increases, the report said.
These changes in the bird world are an indicator of the impact of climate change on humans, Butcher said.
"This isn't something that's going to happen in the Arctic or the Antarctic and it isn't something that's going to happen way off in the future," he said. "It's something that has been occurring over 40 years and it is disrupting the lives of birds and it's going to disrupt the lives of people as well."
Butcher said the key to combating global warming is to pass a law to cap and trade climate-warming greenhouse emissions. - Reuters