Pea Island tower among hundreds helping to track migrating birds

A tundra swan spreads its wings at Pea Island National Wildlife Refuge in Rodanthe, NC, on Monday, Nov. 25, 2019.

A tiny sanderling, a shorebird seen frequently on the Outer Banks, “pinged” as it flew by Pea Island National Wildlife Refuge last summer.

A miniature device on its back emitted a radio signal received by a tower at the refuge’s visitor center located on N.C. 12 south of Nags Head.

The signal showed that this sanderling was tagged on June 30, 2018, on an island in the Arctic Circle. He pinged at Pea Island 19 days later after flying some 3,000 miles.

“This little guy came a long, long ways,” said Becky Harrison, supervisory refuge biologist with the U.S. Fish and Wildlife Service.

The Pea Island tower is part of a system of 887 Motus stations erected all over the world to collect data from tagged animals, especially small migratory birds. Nearly 22,000 animals representing 204 species have been tagged, according to Bird Studies Canada, which initiated the Motus system six years ago.

A nanotag, smaller and lighter than a dime, is attached to the bird’s back. It sends out pulses of radio signals picked up by the Motus towers set at the same frequency. The tower captures the signal when the bird passes within 15 kilometers.

The technology augments bird banding and GPS tags typically used on heavier animals. One drawback is battery life ranges from 10 days to three years depending on the size.

Each ping identifies the specific bird and when and where it was first tagged. The information collected could help determine bird habitats, breeding and nesting tendencies and behavior not known before.

Dozens of studies have been done using the Motus data.

One study in Canada showed that sanderlings had predictable flight patterns and could collide with offshore wind turbines if the array was too close to the beach.

Robin-sized sanderlings are a favorite shorebird to watch on the Outer Banks. The light-colored birds gather in groups as they eat tiny sea creatures on the wet sand when the wave recedes, then retreat together as the next wave crashes.

Another study showed shorebirds migrated north more quickly before breeding, but flew at faster speeds south with more stopovers after breeding. Evidence showed they flew faster to avoid predators, a behavior that reduces mortality after breeding.

In this region, Motus stations are set up at refuges at Pea Island, Back Bay, Mackay Island, Mattamuskeet and Cedar Island. The Pea Island tower has received about 70 pings since the antennae were put up in 2016, Harrison said. She uploads the data about once a month, making it available to scientists worldwide.

“I love the idea of it being collaborative,” she said.

The Pea Island refuge sits along the Atlantic Flyway and attracts thousands of waterfowl and shorebirds. Motus data could help scientists learn more about bird behavior at the refuge, she said.

During a hot spell in May, colonial water birds arrived three weeks earlier than usual. That raised questions. Could that be a long-term behavior because of warmer temperatures? Do refuge biologists need to be ready earlier to place buffers around nests?

Maybe the early arrival is a good adaptation. Maybe it’s better to nest early and get away before the storms hit, she said.

More in-depth evaluations of the Motus data could answer some of those questions, she said.

Jeff Hampton, 252-491-5272, jeff.hampton@pilotonline.com

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