Wednesday, May 14, 2008

Feathers are ruffled for birds in downcounty

Birds may bounce back from disease, global changes

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Laurie DeWitt⁄The Gazette
Patty O’Malley of Germantown searches for a Baltimore Oriole along with other birders on May Count Day Sunday morning at Riley’s Lock in Dickerson.
Mike Bowen hopes Montgomery County is for the birds.

The Bethesda bird enthusiast rattles off species names with the ease of a person double-checking a grocery list — and some of those species, it seems, disappeared in recent years.

‘‘There’s no question that crows were definitely affected by West Nile [virus],” he said. ‘‘Same thing with Carolina chickadees and tufted titmice.”

The Carolina wren, however, is flourishing in the downcounty thanks to fewer cold winters, Bowen said.

Bowen and others who track breeding and migratory birds have seen drastic population fluctuations in the Beltway suburbs in recent years.

The birds survive and dwindle for a host of reasons, from disease to deforestation south of the Equator.

‘‘Many of those species that live in the suburbs are the most adaptable ones, because it’s a highly altered landscape,” said David Curson, bird conservation director for Audubon Maryland-DC.

Woodpeckers and robins are ‘‘doing really just fine,” Curson said. More worrisome to him are the birds that rely on natural habitats such as marsh lands.

It may be tough to identify how Beltway bird population shifts compare with birds in the rest of the United States, he said.

‘‘In a sense there’s a bias built into that, because you’re looking into the successful ones,” Curson said of bird species in Bethesda, Chevy Chase and Potomac areas.

But songbirds are showing a significant decline, according to bird trackers.

Complicating the issue is that counting birds is a detailed and sometimes unreliable project. Statisticians can balance the numbers, Bowen said, but one bird in the wild may be counted by several people or seen by none.

The Audubon Naturalist Society in Chevy Chase ends its ‘‘Bloomin’ Birdathon” in a few days. The month-long event raises funds while participants take down counts of birds and wildflowers.

The event straddled last weekend’s annual ‘‘International Migratory Bird Day,” the unofficial but generally accepted time for counting birds in migration throughout the country.

On Sunday, Bowen led a group of about 20 birders on a tour along the C&O Canal to scope out this year’s flocks.

And while condominiums, new three-story houses and commercial development have altered the landscape of Bethesda and Chevy Chase, the C&O Canal looks roughly the same as it did 25 years ago, Bowen said. As a habitat, it has remained static for the Carolina wrens or cerulean warblers who nest there.

But warbler counts in Maryland aren’t doing so well after all, Bowen said. He noticed following a 2006 bird count along the canal.

‘‘The cerulean warbler had completely disappeared,” he said.

The bluish warblers migrate to forested mountainous regions of South America during winter months but return to Maryland and other eastern states during breeding season.

‘‘That may reflect what’s happening to some of those ... insect eating birds that can’t live here in the winter,” he said.

Advocates have claimed a devastating decline of up to 80 percent in the cerulean warbler population and blamed the loss in part to clearing of eastern forests.

Bluebirds also haven’t fared well in the downcounty — or at least on the sprawling tree-laden campus of the National Institutes of Health in Bethesda.

Bluebirds, chickadees, tufted titmice and crows have been hard hit in the past few years, said Lynn Mueller, chief of grounds maintenance and landscaping at NIH.

About four or five years ago, crows were ‘‘literally falling out of the air. We had quite a program going of picking up dead crows and disposing of them,” Mueller said.

House wrens on campus seem to be at healthy numbers, although NIH counted fewer in 2007 than in previous years, he said.

‘‘Last year, 2007, we saw quite a drop in our bluebirds that fledged,” or left the nest, Mueller said.

The agency in 2002 started counting bluebirds in bird houses along eight campus trails. The trail count’s ‘‘main emphasis is on bluebirds in the Beltway,” he said.

Fledgling bluebirds went from 13 in 2002 to 31 in 2004. And the number climbed higher to 37 fledglings in 2006. But last year, the number dropped by almost one third. Only 14 baby bluebirds left the nest at NIH last year.

‘‘This year, we have a few more nesting birds than what we had for the start of last year, so the population hopefully is picking up,” Mueller said.

He will know for sure in a few weeks, when the first fledglings of the season will fly away.

‘‘All the songbirds seem to be in decline,” he said, but like bird enthusiasts in Montgomery County, Mueller could not pinpoint for sure what is causing distress.

Mueller did say that he doesn’t believe construction on the NIH campus has anything to do with the decline because ‘‘the vast majority” of bird houses are inside the treed buffer zone between the campus and its neighbors.

Now the agency is trying to attract insect-eating birds to help control insect pests on campus. That would cut down on dangers of West Nile virus transmission to humans and other birds, again cutting their populations.

‘‘Hopefully the worst is over,” Mueller said. ‘‘Hopefully it’s bottomed out.”