Study Shows Deep Declines In Shorebirds

By Peter B. Lord
ALL THE NUDESTS, sunbathers and surfcasters who gave up space on some of Rhode Island’s beaches in recent years so biologists could work to protect the nests of endangered Piping Plovers now can see another strong piece of evidence that the work was worthwhile.

The federal government announced last week that a major survey of migrating shorebirds has found dramatic declines in southeastern Canada and the northeastern United States.

The average decline for 30 species studied amounted to 36 percent during the survey period, from 1980 to 2000, according to the study released by the U.S. Geological Survey, a division of the Department of Interior.

Some species fared worse: Black-bellied Plovers declined by 65 percent, American Golden Plovers were down 78 percent, Killdeer dropped 63 percent and species of sandpipers were down from 61 to 74 percent.

“I think this has been a dramatic change,” Jonathan Bart, a geological survey biologist and lead author of the study, said in a telephone interview from Idaho. “It is certainly a cause for concern.”

Piping Plovers also declined throughout the region. But in Rhode Island and Massachusetts, where concerted efforts were made to protect their nests and young birds, the numbers are up dramatically.

“There are places such as Massachusetts and Rhode Island where Piping Plover management was superb — focused and well-managed,” said Brian Harrington, a biologist emeritus at the Manomet Center for Conservation Sciences on Cape Cod, who was a co-author of the report.

The overall numbers for the plovers are down for the region, Harrington said, because places such as the Canadian Maritimes and some other states have not had such effective recovery programs. (The overall decline appears to be more than 50 percent, Bart said, but he wants more data before finalizing that figure.)

So while biologists can celebrate the success stories with Piping Plovers, they can only express concern over the overall declines for shorebirds and a frustration over the lack of explanations.

Shorebirds are not ducks or gulls or cormorants. They are the several dozen species that generally have long legs, pointed wings and long bills. Many nest in the Arctic and migrate through the Northeast to spend their winters in South America. The Piping Plovers are an exception–they nest in the Northeast. Bart said the numbers of shorebirds appear to be declining wherever surveys are done.

“There is a big effort across the world to gather more information and to digest it,” Bart said. “Our big problem in the bird monitoring world is not data, but data management.”

Harrington said data management is the skill that Bart brought to the project. The bird surveys were done by about 2,000 volunteer birdwatchers carefully collecting data every 10 days as part of the International Shorebird Survey coordinated by Manomet.

Bart brought a “special talent” for analyzing the data collected and using it to reach conclusions, Harrington said.

Shorebirds, as they migrate south from the Arctic each fall, touch down in places in the Northeast where they can store huge quantities of food that will fuel them for their long flights on to South America.

The study was not able to discount the hypothesis that the birds simply changed their migratory routes. But, there was no evidence to support that theory either. Frustrating all the scientists is the lack of good evidence to explain the declines.

“Something could be going on in the Arctic. Something could be happening at the coastal sites where they feed. Or, it could be changes in South America,” Harrington said. “It’s an awesome challenge to rigorously sort out the why.”

He said scientists are looking at loss of habitat in general, loss of pond habitat in New England, lower productivity of salt marshes, the filling in of coastal ponds and decreased food supplies because of pollution.

Another concern is climate change. As they migrate, the birds depend on a specifically timed abundance of invertebrates to feed on in each hot spot where they touch down.

“We know they travel in a stepping-stone fashion, one biological hot spot to another. And global warming is throwing the synchronism of biological blooms out of kilter.”

Bart said two broad efforts are under way to try to understand the bird declines. One program is trying to do surveys in places where the birds spend their winters. Biologists also are trying to design surveys that cover the entire continent, Bart said.

The bird study was published last year in the Journal of Avian Biology and can be obtained for a fee. But a summary can be found on the USGS Web site. –Providence Journal