Global Warming Pushes North American Birds Northward

Sophisticated computerized analysis of data gathered during Audubon's Christmas Bird Counts since 1968 show that 58 percent of the 305 widespread species that winter on the continent have shifted north, some by hundreds of miles.

"Experts predict that global warming will mean dire consequences, even extinction, for many bird species, and this analysis suggests that that the process leading down that path is already well underway," warned Audubon President John Flicker during a conference call with reporters today. "We're witnessing an uncontrolled experiment on the birds and the world we share with them."

"Too many people who hear about melting glaciers, polar bears, and changing weather conclude that the impacts of global warming are happening far in the future and far from home. Now they can witness the impact global warming is having with the birds they see or don't see right outside their doors," said Flicker.

Purple finches like this one are moving their range north into the Canadian boreal forest. (Photo by Ashok Khosla courtesy National Audubon Society)

Purple finches shifted their range by 433 miles, pine siskins showed a shift of 288 miles north, and boreal chickadees have retreated north into the Canadian boreal forest a distance of 279 miles, the Audubon data shows.

The boreal forest is important as a refuge for stressed species as they move north, says biologist Dr. Terry Root of Stanford University's Center for Environmental Science and Policy.

While some of the boreal forest has been logged or mined, a lot of it is still untouched, said Root. "We need a place where species can go to take refuge so when it starts getting cooler again they can come out from that refuge."

Waterfowl such as red-breasted mergansers have shifted their range north by an estimated 317 miles, the study shows, while ring-necked ducks have moved north an estimated 219 miles, and American black ducks have moved an estimated 182 miles north, according to Audubon data.

Still, these wetland-dependent species are likely to be affected by the increased drought expected in many parts of North America as global warming worsens and the wetlands they need for survival dry up, the study warns.

Red-breasted mergansers like this one depend on wetlands for survival. (Photo by Dave Menke courtesy USFWS)

"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," said co-author of the report and Audubon director of bird conservation, Dr. Greg Butcher.

"Common sense dictates that we act now to curb the causes and impacts of global warming to the extent we can," he said, "and shape our policies to better cope with the disruptions we cannot avoid."

Grassland bird species have moved the least but not because they are not under stress. These birds cannot find new habitats farther north because the grasslands have been converted to row crops, pastures, and hayfields. So, the study finds, only 10 of 26 grassland species moved north, while nine species were forced south.

In combination, global warming and ongoing use of grasslands by humans will doom grassland birds such as the eastern meadowlark and the burrowing owl to continued population declines, the study indicates.

How much of their range various species will lose depends on how rapidly humans can curb their greenhouse gas emissions.

Dr. Gary Langham, Audubon California director of bird conservation, the yelllow-billed magpie, found only in California, could lose 80 percent of its range if humans continue to emit high levels of greenhouse gases, or the species could lose just five percent of its range if humans lower their emissions quickly.

The yellow-billed magpie is found only in California. (Photo by Ashok Khosla courtesy NAS)

Betsy Loyless, Audubon senior vice president for policy, told reporters that the nonprofit organization's legislative agenda is shaped by the needs of birds and humans to curb global warming.

Audubon supports mandatory limits on global warming pollution and a cap-and-trade program that is consistent with preventing average global temperature from rising another two degrees Fahrenheit.

Loyless says lawmakers should promote energy efficiency and renewable energy legislation that will serve as a "down payment" toward the goal of a 60 to 80 percent reduction in greenhouse gas emissions by 2050.

State and federal lawmakers should adopt policies designed to increase energy efficiency by at least 15 percent by 2020, she said.

A national renewable electricity standard that will require 25 percent of all electricity to be provided by renewable resources by 2025 is another Audubon goal. This goes hand in hand with the development of properly-sited transmission lines to serve new renewable energy sources and a smart grid to transmit that energy more efficiently.

Audubon anticipates that the new evidence will help attract attention and spark action among more than 40 million U.S. birdwatchers, including tens of thousands who contributed to the Christmas Bird Count data on which the study is based.

The 109 year old Christmas Bird Count census provides the world's longest uninterrupted record of bird population trends.

"Citizen science is allowing us to better recognize the impacts that global warming is having here and now," said Butcher. "Only citizen action can help us reduce them."

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