Birds move north; global warming cited

Minnesotans have been getting used to seeing robins all winter. But the birds' increasing presence here in January represents a "major ecological disruption" in response to global warming, National Audubon Society officials said Tuesday.

In a study using data from 40 years of its national citizens' Christmas bird count, the society found that 58 percent of the wintering bird species its counters have tracked have moved their winter quarters northward, some by hundreds of miles.

From 1966 through 2005, the study period, the average U.S. January temperature rose more than 5 degrees.

For birdwatchers in Minnesota, the result has been an explosion in the winter population of many species, from hairy woodpeckers to tundra swans. But it also brings home, said Mark Martell, director of bird conservation for Audubon Minnesota, what climate scientists have been predicting -- that a warming climate will challenge animals and plants to move or adapt to new conditions. "It's not just about polar bears. It's also about robins in Minneapolis," he said.

Generally speaking, warmer winter temperatures mean many species don't have to fly as far south to stay warm.

Food supplies also might continue to be available farther north.

The Audubon study found that of the 305 wintering species its members have tracked on the annual one-day count, 177 are now centered north of where they were in 1966, by an average of 35 miles.

That average includes the distance that a few species, including the western meadowlark, moved south. While birds change their nesting and feeding areas often and for many reasons, the fact that so many species have moved toward higher latitudes suggests that climate change is the cause, Martell said.

The farthest shift in the Audubon study was accomplished by the purple finch. The center of its winter distribution has moved 433 miles north, from far southeastern Missouri to north central Iowa. The red-breasted merganser was one of the longest-distance movers over the recent four decades, shifting its center 316 miles from northeastern Kansas to southwestern Minnesota.

Audubon officials and others in a news conference Tuesday said the findings should add more urgency to the need to develop alternatives to fossil fuel use, seen as the chief cause of global warming.

Minnesota has more than 100 winter bird species, Martell said. Many are increasing their populations both in Minnesota and across the continent.

But the Audubon study cited three species already centered north of the state -- the boreal chickadee, the American three-toed woodpecker and the Bohemian waxwing -- as retreating.

"There's potential for them pulling out of the state," said John Curry, policy director for Audubon Minnesota.

A majority of grassland birds have not followed the northward drift, perhaps because they can't find habitat to move to, said Alicia King, communications coordinator for the U.S. Fish and Wildlife Service migratory bird division.

King said the Audubon report contained few surprises for birdwatchers. What's uncertain is whether birds that have moved will thrive in new places -- and what impact they'll have on birds and other wildlife that are already there.

"We do know there will be some negative impacts due to climate change," King said.

The service is beginning to develop a comprehensive look at those impacts on all wildlife, King said, and is releasing its own report on the state of birds in the United States next month.

King also praised the Audubon report for relying on "citizen science."

The Audubon Christmas Bird Count began in 1900 and in Minnesota in 1906. The recent report doesn't include trends in birds' winter locations prior to 1966. There were 49 counting circles of 15-mile radius in Minnesota's 2008 count; birdwatchers noted 129 species and more than 250,000 birds.

Bill McAuliffe • 612-673-7646

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