Study finds steep drop in Bay State’s native birds
The melancholy whistling of the yellow-bellied eastern meadowlark had long been heard in hay fields and salt marshes throughout Massachusetts. The American kestrel, the continent’s smallest falcon, thrived in local grasslands, hunting for grasshoppers, mice, and other prey in the state’s once-abundant farms. And the red-eyed eastern towhee long warbled in wooded areas while noisily raking the brush-covered grounds to forage for insects.
Those birds as well as many others are disappearing from Boston to the Berkshires, while wrens, woodpeckers, and other species from Southern states are mysteriously taking their place and surging throughout Massachusetts, according to a landmark report by Mass Audubon, which compiled decades worth of data about the state’s birds from thousands of scientists and trained birders.
The report found nearly half of all the state’s breeding birds are declining, including many marshland and grassland species as well as more common birds such as blue jays and swallows, raising questions about the health of the state’s wetlands and other ecosystems.
It also found that although the state has helped bring back endangered birds such as piping plovers, peregrine falcons, and bald eagles, 20 of the 28 birds listed under the Massachusetts Endangered Species Act remain vulnerable. An additional 34 birds that have been identified as of “conservation concern’’ were also found to be declining.
“As a longtime observer of the natural world, I am alarmed by the challenges facing many Bay State bird species,’’ wrote Edward O. Wilson, the biologist from Harvard University, in a letter introducing the report titled “State of the Birds.’’ “My concern is not simply for the loss of birdlife, but that birds as nature’s heralds are signaling broader ecological deterioration.’’
He added: “This report captures the changes in bird distribution that seem to be unmistakable markers of climate change.’’
Among the other findings: More than a quarter of all wintering birds are in decline; the number of species that are increasing has fallen by half since 1980; and the number of ground-nesting birds and others that feed on insects are dropping.
The report, which surveyed more than 300 birds, notes that some declines are to be expected as Massachusetts continues to lose its agricultural lands to development and suburbs replace farmland, but the authors say in the report that there is “a real risk that we could lose some of our native birdlife.’’
It also cites warming temperatures, toxic chemicals, and feral cats and other predators for the changes in the bird population.
“This report shows that in a state of 6.5 million people we need to plan our growth better,’’ said Tom French, assistant director of the state Division of Fisheries and Wildlife, who oversees the state’s endangered species programs. “We need to grow in a thoughtful way that will build in the best places to build and preserve the most important natural resources. Having a state that’s environmentally healthy is an asset to the human population, too.’’
The report bases its findings primarily on three surveys that for years have tracked the state’s birds. The surveys involve trained birders walking the same routes in different years around the same time, counting all the birds they encounter.
In one of the surveys, the Massachusetts Breeding Bird Atlases, volunteers counted birds by dividing the state into 9-square-mile blocks. By comparing data from two survey periods, 1974 to 1979 and 2007 to 2011, the report identified that 60 percent of state birds were increasing, 24 percent declining, and the rest were deemed stable.
Among the steepest increases were wild turkeys, which went from being found in 16 blocks to 674; red-bellied woodpeckers, which rose from four blocks to 640; Carolina wrens, up from 43 blocks to 594; and the Canada goose, which went from 281 blocks to 747. Great blue herons, Cooper’s hawks, and the common raven also multiplied.
The largest decreases included the Eastern meadowlark, which dropped from 371 blocks to 89; the ring-necked pheasant, down from 341 blocks to 77; and the American kestrel, which fell from 425 blocks to 176. Other birds with precipitous declines included the white-throated sparrow, the brown thrasher, and the purple finch.
In another study called the North American Breeding Bird Survey, which provides bird counts from numerous 25-mile routes across the state going back to 1966, nearly half of all birds were found to be declining, while only a third were increasing. Two-thirds of all the birds surveyed in the state are breeding birds.
In a tally of winter birds called the Christmas Bird Count, the report found that between 1963 and 2008 the birds that remain in Massachusetts through the cold increased by nearly 60 percent, while more than a quarter are declining.
“When you combine these studies and others, we for the first time ever were able to create a report card for the health of the bird populations in Massachusetts, which allows us to decide how to spend money and time,’’ said Joan Walsh, director of bird monitoring for Mass Audubon and an author of the report.
The researchers said the proliferation of birds that were once only found in small numbers in the southern part of the state suggest climate change may be playing a role. They note that as winter temperatures have increased by 1.3 degrees every decade since 1970, it appears to be affecting the timing of migrations, the food available, and the type of trees suitable for nesting.
They said the changes in the state’s bird population are likely to increase over the next century as the state’s climate becomes more like Baltimore’s.
The report recommends the state do more to mitigate climate change, preserve critical habitats in wetlands and other areas, and protect undeveloped land.
“The most important take-away of the report is to realize that we do have an impact on birds, and for some of them, we have an ability to increase their population,’’ said James DeNormandie, a conservation planner at Mass Audubon and an author of the report. “It’s our responsibility as stewards of the environment to help preserve and create the habitat they need. Birds act as indicators of the quality of the world we live in.’’