Study: Clark’s nutcracker survival may rely on whitebark pine

Several decades ago, the gray and black Clark’s nutcracker seemed as common in its home ranges as robins. If you went for a hike in the mountains where whitebark pine grew — Glacier National Park and the Greater Yellowstone Ecosystem — you’d likely see a Clark’s nutcracker.

But the bird began to vanish as the invasive fungus “blister rust” and the unrelenting outbreak of mountain pine beetles climbed to higher elevations, killing whitebark pines in the Greater Yellowstone.

Taza Schaming, a doctoral student at Cornell University, is studying the relationship between the Clark’s nutcracker and whitebark pine. She’s spent seven years researching the birds so far, and the work is yielding first-of-its-kind data that could help resource managers better understand the bird and whitebark pine forests.

Scientists knew little about the birds, including how many exist, when Schaming started her study. “Anecdotally, we know the birds are declining in a lot of the range,” she said. But there are no hard numbers on historic or current populations.

Clark’s nutcrackers live in remote, and often hard-to-reach places at high elevations where whitebark pine grow. The tree exists through obligate mutualism with Clark’s nutcrackers: whitebark pine can’t survive without the birds because they open the tree’s cones, remove the seeds, disperse and bury them. A single Clark’s nutcracker can hide up to 100,000 seeds a year.

“Whitebark pine has no other means for regeneration,” Schaming said.

In turn, Schaming found the birds are dependent on the trees. She knew the birds ate new whitebark pine cone seeds and stashed mature seeds for a later harvest. But she didn’t know just how dependent on cone production the birds are, especially when it comes to reproduction.

In her study, Schaming fit 76 birds with radio transmitters that emit a signal up to 30 miles. The tracking device allowed her to see what the birds were eating and where they were going. It also led her to the birds’ nests.

In 2009 and 2011, years directly following low whitebark pine cone production, the birds unexpectedly stopped breeding. Completely. In 2012, however, all but two of the birds bred.

“I need more years of data, but it could be pretty serious if it is the whitebark cone crop driving breeding,” she said.

Schaming also found that when the birds do breed, they use Douglas firs at lower elevations for breeding habitat and an alternate food source, showing they need a healthy forest, not just one species of tree, to thrive.

This year, Schaming fit seven birds with satellite trackers, allowing her to follow the birds when they left the Greater Yellowstone. One bird flew south to the Grand Staircase Escalante National Monument in Utah. Another flew to the Utah-Wyoming border. Another flew 200 miles north into Montana and then returned to the Greater Yellowstone.

Schaming knew Clark’s nutcrackers can travel great distances; one year, during especially poor whitebark pine cone production in the West, they flew en masse to Pennsylvania. But this year was an average year for cone production.

Although the sample size is small — Schaming is hoping to secure funding for more satellite trackers — more than half the birds left the ecosystem, showing the birds use large swaths of space even during healthy cone crop years. And the birds she tracked via radio transmitters flew across the ecosystem, sometimes crisscrossing the Tetons daily.

“These birds need a much larger habitat area for their everyday, annual existence,” Schaming said. “I think the scale is huge. It puts in perspective just how much habitat we need to protect Clark’s nutcrackers.”

Previous research showed that to thrive, the birds need 1,000 whitebark pine cones per hectare — which is about 2.5 acres. While the statistician Schaming is working with hasn’t finalized the numbers, the actual concentration of whitebark pine cones is “much, much lower” in the Greater Yellowstone, she said.

The information is incredibly important as land managers try to restore decimated whitebark pine forests, said Bob Keane, a research ecologist at the Rocky Mountain Research Station with the U.S. Forest Service. Whitebark pine is a candidate for the endangered species list and will likely eventually be listed, he said. Yet scientists know little about the regeneration dynamics of the trees, which support about 110 species.

“If you don’t know much about the nutcracker, you don’t know how to regenerate the species,” Keane said. Schaming’s research already has increased understanding of the birds’ life cycles and population dynamics, he said.

It also is an important reminder about the importance of protecting a habitat mosaic, not just a single species, Schaming said. Everything is connected. While the whitebark pine is the only tree entirely dependent on the Clark’s nutcracker, the birds disperse the seeds of about a dozen conifer trees in the West. And while they aren’t the only species to spread the trees’ seeds, they often take them farther than rodents or the wind, Schaming said.

Schaming’s research has already expanded what is known about Clark’s nutcrackers, but it’s just a start. She’s still gathering data daily and plans to return to Wyoming in the spring to continue her research, fitting more birds with satellite transmitters.

— This story has been updated to correct the number of whitebark pine seeds a Clark’s nutcracker can distribute. — Ed