Sprawl, big farms put common U.S. birds in decline

WASHINGTON (Reuters) - Some common U.S. birds -- like sparrows, chickadees and meadowlarks -- are in deep decline due to suburban sprawl, big agriculture and pesticides, the National Audubon Society reported on Thursday.

Twenty of the most familiar "backyard birds" in North America have lost more than half their populations in the last four decades, said Greg Butcher, the society's conservation director.

These birds are not endangered, but the drop in their numbers is a sign that their grassland and shrub habitats are also on the wane, Butcher said.

"The focus isn't really on what's happening to these 20 birds, but what's happening to their environment," he said. "We see birds as indicators of the health of the environment."

Part of the problem is the U.S. shift over the last half-century from smaller farms that grew varied crops to bigger monoculture farms with larger fields and fewer hedgerows between them. Hedgerows helped support grassland birds.

In places like the U.S. Northeast, farming has been abandoned in some areas in favor of suburban development or turned back to forest, Butcher said, "so there just really isn't any space left for these grassland and shrubland birds."

Pesticides can work against birds in two ways, he said.

Birds can be poisoned by pesticides meant for weeds or insects. But even if pesticides work as intended and only kill weeds and insects, this eliminates two sources of food for wild birds.

"Pesticides help make monocultures much more sterile ... and farmlands are even less likely to provide what birds need," Butcher said.

The demand for corn-based ethanol is tempting some farmers to put back into production land that was set aside for conservation.

"We think it's going to be bad for soil, bad for water pollution, as well as being bad for birds," he said.

Global warming is also a factor. Many of the birds in decline are native to northern forests where longer warm seasons mean more predators and more pressure on birds.

The Northern Bobwhite quail has declined by 82 percent since 1967, according to the Audubon report, which relies on figures from the U.S. Geological Survey's breeding birds survey and the society's 107-year-old Christmas bird count.

Others in steep decline include the Evening Grosbeak, the Northern Pintail, the Greater Scaup, the Boreal Chickadee, the Eastern Meadowlark, the Common Tern, the Loggerhead Shrike and the Field Sparrow.

More information is available online at audubon.org.