WASHINGTON — Some of the nation's most common birds are disappearing at alarming rates.
While loss of such habitat as fringe forests, grasslands and wetlands is believed to be the culprit, there are mounting concerns that global warming could be starting to take a toll.
Over the past 40 years, populations of the northern bobwhite are down 82 percent and have virtually vanished from parts of its range. Populations of evening grosbeaks and northern pintail have dropped by nearly 78 percent, greater scaups by 75 percent and Eastern meadowlarks by 71 percent, according to a new Audubon Society analysis of bird count and breeding records.
"These are not rare or exotic birds we are talking about - these are birds that visit our feeders and congregate at nearby lakes and seashores, yet they are disappearing year by year," said Carol Browner, Audubon chairman and a former U.S. Environmental Protection Agency administrator. "Their decline tells us we have serious work to do, from protecting local habitats to addressing the huge threats from global warming."
After reviewing data from its annual Christmas Bird Count and the U.S. Geological Survey's annual Breeding Bird Survey, Audubon published a list of 20 birds whose populations have fallen by more than half since 1967. Other birds on the list include whippoorwills, common terns, snow buntings, little blue herons and Rufous hummingbirds. (Detailed information on the analysis along with audio of the birds' calls is available at www.audubon.org.)
The declines aren't uniform across the nation. In Washington state, evening grosbeak populations are down 97 percent.
"I haven't seen an evening grosbeak in my backyard this year," Nina Carter, executive director of Audubon Washington, said of a bird that was a frequent visitor in years past to her Olympia, Wash., neighborhood. "What's happened is pretty incredible."
Though Carter said she's often been accused of overusing the phrase, she likens the drop in the number of common birds to a "canary in the coal mine." Miners used to carry canaries into the mines. If the birds died, the miners knew poisonous gases were building up in the shafts.
"This isn't so much about the birds, though that is important," Carter said. "It's what it means for people, for the environmental health of our communities."
Nationally, critical common bird habitat is under pressure from urban sprawl, energy development and even the nation's drive to grow more crops for biofuel, Audubon found.
Suitable habitat for the northern bobwhite is shrinking. The prairie pothole breeding ground of the northern pintail is disappearing because of expanded agricultural activity. Wetland loss and degraded water quality are affecting the food supply of little blue herons, and greater scaup populations are affected by the melting of the northern permafrost.
Meanwhile, such suburban species as geese, robins, crows and some populations of gull are thriving, said Greg Butcher, who headed the Audubon analysis.
"Some of these are getting more abundant than we would like," he said.
Butcher said he doesn't expect any of the common birds to go extinct, but added that steps need to be taken to protect them, including dealing with the challenges of global warming.
"We know a number of species, robins, bluebirds, crows, are wintering farther north," Butcher said. "It's a clear signal they are responding to global warming. We've seen it, but (global warming effects) are hard to quantify. My guess is we will find it."
While clean air, clean water, land use and global warming are often bound up in politics, Carter said individuals can take such simple steps as planting more native plants in their yards or cleaning their bird feeders regularly before the feed can spoil and turn moldy.
"This analysis give us a baseline to track this problem," she said. "It also helps us understand the clear connection between birds and habitat and our communities."