Leslie Clapp only began birding in 1999, too little time, she says, to see trends in local bird populations. But as president of the Downeast chapter of the Maine Audubon Society, she’s heard from other members that once-common birds, like the evening grosbeak, have vanished.
“Decks…would be full of 30 to 50 [evening grosbeaks],” Clapp said. “They’ve always been so common and now they’re not around.”
Clapp said she regularly hears of new threats to individual bird species, be it West Nile Virus, wind power or development.
“You read it every day,” she said.
But a new report from the National Audubon Society warns that birds in the U.S. may be in bigger trouble than anyone previously suspected. The report found that out of 600 species of common birds in North America, about one-third of the species lost population in the last 40 years, with dozens of species in dramatic decline.
The report is the first to analyze four decades’ worth of combined data from Audubon’s Christmas Bird Counts and from the Breeding Bird Survey, an annual count organized by the U.S. Geological Survey and carried out by volunteers every May through July.
The data showed the populations of 20 common birds declined by 50 percent or more across the four decades. Fourteen of those 20 species live in New England seasonally or year-round. The number of evening grosbeaks is down 78 percent, for example; the boreal chickadee, down 73 percent; the eastern meadowlark, down 72 percent; and the common tern down 71 percent.
Greg Butcher, director of bird conservation for the National Audubon Society and co-author of the study, said bird populations are declining because humans are using up natural resources at an ever-increasing rate.
“We’re competing for the same habitat,” Butcher said.
The study’s authors blame bird decline on the effects of global warming and a loss of habitat — from sprawl development within the United States, and from deforestation in Central and South America, where many migratory birds winter. Radar imaging has documented fewer migratory birds entering the United States, according to the study. And birds that make it across the border still face loss of habitat at a rate of 500,000 acres a year.
Bird populations have long been considered an indicator of overall environmental health. The United Kingdom uses bird counts to gauge environmental quality and set policy. Audubon officials say the sharp decline in bird populations found in the new study should be viewed as a canary in the coalmine; whatever hurts bird populations may soon hurt humans, they warn.
“Birds are showing us that what we’re doing to the environment is not sustainable,” Butcher said.
Susan Gallo, a wildlife biologist with Maine Audubon, said Maine is critical habitat for many different bird species. New England serves as a stopping point for both southern and northern migratory birds. Maine is particularly attractive to birds, with one of the last stands of uninterrupted forest in the north, good farm fields inland and the longest stretch of undeveloped coastline of the eastern seaboard. Maine shorefront access, in particular, is essential for many migratory birds, Gallo said.
“They need to stop to eat or else they won’t make it,” she said.
But those three critical habitat areas are under pressure from human activity and development, she said. Vast tracts of northern woodlands are being subdivided, old farm fields are reverting to poor forest habitat, remaining fields are being mown during grassland birds’ nesting season, and waterfront access is being lost to increased housing development, beach use, and new waterfront infrastructure.
Although the message of the Audubon report is dire, bird experts say much still can be done to preserve key habitat and halt the decline of specific species. Through concerted effort, some birds that were rare in Maine 40 years ago have rebounded. The bald eagle has come off the endangered species list, wild turkey range is larger than before Europeans arrived in North America, and endangered piping plover numbers have increased ten-fold since the mid-1980s.
Gallo said Maine Audubon will continue to push for legislation to protect critical wetland and coastline bird habitat. But Gallo and Butcher both said small landowners can do much to help troubled bird species, including mowing fields in mid-July rather than June, setting up bird feeders, and leaving brush piles for nesting birds.
“It starts with what people can do in their backyard,” Butcher said.
Hill Country Observer editor Fred Daley contributed to this report.