Birds' movements reveal global warming threat.

Analyses of citizen-gathered data from the past 40 years of Audubon's Christmas Bird Count reveal that 58% of the 305 widespread species that winter on the continent have shifted significantly north since 1968, some by hundreds of miles. Movement was detected among species of every type, including more than 70% of highly adaptable forest and feeder birds. Only 38% of grassland species mirrored the trend, reflecting the constraints of their severely-depleted habitat and suggesting that they now face a double threat from the combined stresses of habitat loss and climate adaptation.

Population shifts among individual species are common, fluctuate, and can have many causes. However, Audubon scientists say the ongoing trend of movement by some 177 species--closely correlated to long-term winter temperature increases--reveals an undeniable link to the changing climate.

"Birds are showing us how the heavy hand of humanity is tipping the balance of nature and causing ecological disruption in ways we are just beginning to predict and comprehend," maintains Greg Butcher, director of Bird Conservation. "Common sense dictates that we act now to curb the causes and impacts of global warming to the extent we can, and shape our policies to better cope with the disruptions we cannot avoid."

[ILLUSTRATION OMITTED]

Movement across all species--including those not reflecting the 40-year trend--averaged approximately 35 miles during the period. However, it is the complete picture of widespread movement and the failure of some species to move at all that illustrate the potential for problems.

Specific models indicate that the magnitude of losses in California, for instance, depends largely on steps taken now to reduce greenhouse gas emissions. The California gnatcatcher could lose as much as 56% of its range, or as little as seven percent, depending on how climate change is addressed. Projected range losses for the San Francisco Bay area's popular chestnut-backed chickadee vary from 49% to as little as 16%.

"The birds are giving us yet another warning that it's time for urgent action," stresses John Flicker, president. "People hear about melting glaciers and changing weather, but now they can witness the impact global warming is having with the birds they see or don't see right outside their doors. These birds are our 'canaries in the coal mine' and they're telling us that we'd better do something fast to curb global warming and to protect habitat."