Shorebirds find a sea of Idaho grass

Biologists work to unlock migration secrets of curlews - and mystery of their decline

rbarker@idahostatesman.comMay 22, 2013 

  • THE LONG-BILLED CURLEW

    Scientific name: Numenius americanus

    Range: The bird often nests in the Great Basin and the Great Plains, and winters from the Carribean through Mexico and west to California.

    Size: Adults weigh about 2.2 pounds and have a wingspan of 24 to 35 inches, making it the largest shorebird in North America.

    Food: Insects, crabs and other invertebrates.

    Nesting: It breeds in grasslands, where the birds go through a sophisticated dance before building a nest in a hollow surrounded by short grass. The male and female alternate sitting on the nest. The chicks quickly leave the nest after hatching.

The long-billed curlew is the nation's largest shorebird, but its fate might lie in the grasslands of Southern Idaho and the Great Basin.

Researchers from the Idaho Bird Observatory at Boise State University are trying to determine why numbers of nesting pairs of the birds have dropped so precipitously since they were first counted on the rangeland between Emmett and the Treasure Valley in the 1970s. The birds spend their winters on shores of seas and lakes, and in wetlands, from the Gulf of Mexico to California. Scientists need to know where these well-traveled Idaho birds go as they work to understand the curlew's life and its threats.

One day this month, a caravan of cars and trucks drove slowly up a dirt road through rolling hills of public land north of Middleton. An observer might have thought they were watching a safari driving through the veldt of Zambia.

The biologists and volunteers were heading to a nest that technician Ben Wright had found after hours of searching. They traveled wide, bare trails pioneered by trucks, ATVs and motorcycles, passing grazing cattle and men with guns shooting ground squirrels. Parasailers soared above the tall, windswept grass.

The area's sagebrush is gone, or limited to small patches, likely from decades-old burns meant to improve the productivity of grasses for grazing. Perhaps, because of the burning, the native bunchgrass is thick and healthy.

"A lot of people see this as a biological wasteland," said Deniz Aygen, a bird biologist and coordinator of the Idaho Fish and Game Department's Watchable Wildlife program. "But you see, with these nuggets of biological diversity, how valuable it is."

CAPTURING MAMA BIRD

Biologists parked a few hundred yards from the nest, and Wright and research biologist Jay Carlisle got out a long net. As they approached the back of the nest, the male flew off, making a sharp "wid, wid, wid" trill. The female hunkered down on her eggs, even when a rancher drove by less than 10 feet away.

Carlisle and Wright carried the net directly over the nest and caught the female. Carlisle carefully grabbed her, leaving her legs loose as instructed by curlew-handling expert Fletcher Smith from the Center for Conservation Biology in Virginia.

Smith was in Idaho to teach the team how to place a satellite transmitter on the back of the curlew. The small, solar-powered unit, which transmits intermittently through the day, will show scientists where the birds go year-round.

"We can sit and watch where she goes on our smartphone," Carlisle said.

Temperatures in the low 80s were just right to leave the four eggs unincubated for the 30 minutes it takes to attach the transmitter.

Inside the air-conditioned pickup cab, Carlisle and Smith placed the transmitter on the curlew's back and made sure it was working. They checked that the gray-and-brown bird was no worse for wear, then research biologist Jessica Pollock released her. The mom returned to the nest after a short flight.

PREDATORS ARE WINDED, ARMED

The nest is in an Area of Environmental Concern, designated by the Bureau of Land Management in 1992. That means the agency seeks to protect the curlew and works with the rancher who owns the cattle that graze in the area.

Still, the number of nesting birds has dropped to between 150 and 300 in counts over the past four years, compared to about 1,000 in the late 1970s, Carlisle said. Curlew reproductive success is very low - 15 percent to 30 percent.

Grazing patterns haven't changed, but the area gets far more recreational use today than in the '70s. The ground squirrel population also appears to be higher, Carlisle said, which might have attracted more ravens and other predators. Biologists have also found dead curlews left behind by shooters.

One possibility, Carlisle said, is that the habitat structure has changed. Curlews like short grass near their nest so they can see any predators approach.

"Some of the areas have become tall and weedy," he said.

Likely, the birds need a mosaic of tall and short grass so they and their chicks can hide after the hatch.

But the birds do spend much of their lives in other places after they leave Idaho, and it could be that changes in the habitat along shorelines and wetlands in another part of the world account for the curlew population drop in Idaho.

"Maybe the issue is on their wintering ground," Carlisle said.

The scientists hope the curlew they've identified and outfitted with the transmitter survives the summer and its trip to winter grounds before returning to Idaho.

"I won't breathe a sigh of relief for nine months when we see where they went," said Smith, the Virgina curlew handler.

Rocky Barker: 377-6484

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