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.
Traditionally, scientists tracking animals had to do so with hand-held antennae that limited them to scanning one animal at a time. The new technology is more efficient, faster and provides a greater range.
“The new technology allows you to put up automated towers with an antenna mounted way high up connected to a computer,” Pau said. “It’s recording all the birds [in that area] at the same time and allows me to uniquely identify each bird.”
On Friday, Pau and other biologists captured 29 semipalmated sandpipers at the Plum Island refuge and fitted them with the nano-tags, as well as traditional metal leg bands and color bands for easy identification.
Pau said the biologists found two sandpipers among the 29 that already had been tagged — in Brazil.
“It’s pretty exciting,” she said. “These birds migrated to northern Canada or Alaska to their breeding grounds and are now on their way back to South America. Presumably, they have made the journey at least once.”
The beauty of the new system of tagging is that by developing a system of towers along the birds’ migratory flyway, researchers will be able to track the birds over much longer distances and periods of time. That should provide them with more answers about not only practical matters such as flight speed and habitat stops, but what might be causing their population numbers to decline.
“We are working within a network of researchers from Canada to Cape Cod, and we all have these automated towers we’ve deployed,” Pau said. “As long as we know each other’s frequencies and the unique code for each tag that we deploy, our towers will pick up each other’s birds.
“And that might help us answer a lot of these questions.”