Consider the semipalmated sandpiper, a wee little thing that seldom reaches more than 6 inches from head to tail.
Small in stature, but large in stamina, these birds breed in the Arctic and winter along the coasts of South America, often after nonstop oceanic flights of up to 2,500 miles from local shores. They are among the most abundant of small shorebirds.
Still, their numbers are dwindling — by as much as 80 percent over 30 years in a recent bird count in northern Atlantic states — and scientists are trying to determine the cause.
“We’re not really sure why their numbers are down,” said Nancy Pau, the wildlife biologist at the U.S. Fish and Wildlife Service’s Parker River National Wildlife Refuge on Plum Island. “A lot of the shorebirds are in decline. There are many theories. It could be habitat loss both on their wintering grounds and along their migration belt or perhaps a predator at their breeding or wintering grounds.”
Many of the birds come through the East Coast, spending time on the beaches and salt marshes of Cape Ann and the North Shore during their fall migration to the south. Their migratory flyway often brings them into contact with development that has shrunk their preferred pit stops and feeding grounds.
“They use beaches, and they use wetlands a lot,” Pau said. Those are areas that have changed significantly in the last 200 years, Pau said.
Pau is part of an international project that could provide some of the answers to questions of what’s happening with the sandpipers.
Utilizing advanced technology, biologists in the United States and Canada have developed a system to track where the birds go, what path they fly and how long it takes them.
The system employs tiny radio-telemetry tags — so tiny that they also are used to track dragonflies — that are glued to the birds’ feathers. The nano-tags, each with a unique code, emit a signal on a prescribed frequency that allows researchers to track the birds more efficiently.