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Common bird populations shrink drastically

Expansion, global warming spur alarming decline in US, Mass.

The United States has seen an alarming decline in common birds over the past 40 years, due to the loss of habitat from suburban sprawl and expansion of commercial agriculture as well as more recent effects from global warming, according to a National Audubon Society study released today.

In Massachusetts, several birds seen regularly three or four decades ago, such as the Northern bobwhite and the Eastern meadowlark, have now become extremely rare, according to the study. Human encroachment on their habitat -- grasslands and shrubs -- has vastly diminished their populations and altered the avian pecking order over the decades, according to annual bird counts.

Even the number of common grackle, a robust species, has fallen by 68 percent in in Massachusetts over four decades, said Greg Butcher, national director of bird conservation for Audubon.

"The grackle is about as common a bird as any out there," he said.

"I was surprised to see it declining in New England. It's probably because the success of the crows gives less space for grackle."

The nationwide analysis looked at data collected by volunteer bird watchers in the Audubon's annual Christmas Bird Count, which started 107 years ago and is held in the 10 days before and after Christmas; and the annual North American Breeding Bird Survey organized by the US Geological Survey every June. Combining the data from both surveys produced a snapshot of 550 bird species from roughly 5,000 sites in 48 states, Butcher said. Alaska and Hawaii have had fewer sites and were not included.

"These are not rare or exotic birds we're talking about -- these are the birds that visit our feeders and congregate at nearby lakes and seashores and yet they are disappearing day by day," said Carol Browner, Audubon board chairperson and former Environmental Protection Agency administrator in the Clinton administration. "Their decline tells us we have serious work to do, from protecting local habitats to addressing the huge threats from global warming."

Butcher said that global warming was affecting birds in numerous ways, including the reduction of habitat in the far north, the destruction of trees in the boreal forests due to proliferation of northward-moving pests, and changing migratory patterns that have shifted north.

"Birds are wintering farther north. In the fall, they are migrating south only as far as need be to survive," Butcher said.

In Massachusetts, Butcher said, volunteers recorded a 62 percent decline in the snow bunting, a bird of the high Arctic, and a 52 percent decline of the greater scaup, a small duck that breeds in Alaska and northern Canada, over the past 40 years, according to the Audubon Christmas counts. Both breeds migrate to Massachusetts.

Scott Weidensaul, a nationally renowned naturalist and author, said that bird watchers have long known about the decline of species in areas where once they were abundant. In eastern Pennsylvania, where he grew up, he said he woke up to the sounds of the bobwhite quail and fell asleep to the sounds of a whip-poor-will, but "today you can't find a bobwhite in Pennsylvania and the whip-poor-whirl is increasingly rare."

The same is true in Massachusetts over the last four decades, according to the bird counts: the Northern bobwhite has declined by 99 percent, and the whip-poor-will by 88 percent.

"For the first time we are able to put numbers to a phenomenon so gradual for so long that it's been easy to overlook -- until this point," Weidensaul said of the study.

Nationally, the steepest declines over 40 years was the Northern bobwhite, down 82 percent. But the drive to produce more ethanol -- a corn-based alternative fuel some say is the key to American energy independence -- has spurred proposals to transform more land into cornfields, further destroying more of the birds' habitat.

John Donnelly can be reached at donnelly@globe.com

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