Climate Change Threatens South Hills Crossbill

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Sunday, June 28, 2015 • A1 www.magicvalley.com • $2.00

June 28, 2015

Climate Change Threatens South Hills Crossbill VIRGINIA HUTCHINS vhutchins@magicvalley.com

HANSEN • The red crossbills of the South Hills and the Albion Mountains are like no others in North America, and they’re in trouble.

There’s something remarkable, too, about these mountains’ lodgepole pines — something integral to the fate of this colorful bird with a highly specialized bill.

The tree and its big-billed seed predator are engaged in a contest of adaptation: pine cone defense versus the forager. That relationship soon could lead to species designation for the South Hills crossbill.

The scientist who described this bird as Loxia sinesciurus in 2009 returns each summer to the South Hills to study the bird’s ecology and population dynamics — and the cause for its massive decline.

Craig W. Benkman, an evolutionary ecologist at the University of Wyoming, is finishing an extensive genetic study and preparing to recommend a second time that the South Hills crossbill, now a call type of the red or common crossbill, be recognized as a distinct species.

“And if it is, it will be one of the most endangered bird species in North America,” he said.

The culprit? Climate change.

Scientists’ climate models predict a major reduction in the distribution of lodgepole pines — including their disappearance by the end of this century from the Idaho mountains that constitute the South Hills crossbill’s entire range.

“The outlook for this bird,” Benkman said, “looks really grim.”

••• On an early morning in June 2014, the cold campfire pit near a South Hills cabin becomes a research station.

This cabin southwest of the Diamondfield Jack Snowplay Area sits on a hillside, so posts support its front porch. Years ago, the cabin’s construction left something salty in the soil below the porch, and Benkman knows the crossbills will come for it.

“Birds come from all over to this spot,” he says. He found it in 2005 and started capturing crossbills under the porch in 2006.

Before 6 a.m., he and his field crew strung mist netting below two sides of the porch. Now the five wait quietly just uphill, where

Nathan Hough, a University of Wyoming undergraduate, holds a South Hills crossbill in June 2014.

PHOTOS BY ASHLEY SMITH, TIMES-NEWS

Craig W. Benkman, an evolutionary ecologist at the University of Wyoming, studies South Hills crossbills each summer. a plank resting on upturned campfire logs serves as their work table.

They’re waiting for crossbills to fly under the porch’s open south side, and they speak softly.

“We’ve got a few in the willows right now,” says Nate Behl, a UW graduate student carrying binoculars.

Some crossbills that fly under the porch will try to leave in another direction and be caught in the nets. When the researchers walk by, their movement will flush the rest.

Already, a couple of crossbills hang from the netting. “Maybe we should go for it,” Benkman says.

But Behl points out the

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crossbills he’s watching in nearby trees. “I’d give it another five minutes. We’ve got lots of birds around.”

When the researchers kneel at the nets, they work quickly and gently to free each crossbill.

“If they’re screaming, it’s very stressful for us,” Benkman says.

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On the cones of lodgepole pines in the South Hills, relatively large distal scales deter crossbills from getting access to underlying seeds. In regions where red squirrels are also present, the tree’s cones are more tapered.

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Crossbill Continued from A1

But these birds are quiet, and even the female with a string of netting caught in her leg band cooperates.

“This is going to be hard,” Benkman says, “because you don’t want to injure their wing. But fortunately she’s being very good.”

Soon each captured crossbill occupies a small cage. Three segmented boxes can hold eight birds each, visible through wire mesh on one side of the box and accessible through a flap on the other.

Before these crossbills can be released, the field crew must quickly take measurements and record the data they need to understand what’s happening to this bird population.

••• The crossbills of the South Hills and the adjacent Albion Mountains are the largest ones north of Mexico and east of Newfoundland, the third largest of the 10 red crossbill types in the Western Hemisphere.

The secret is in the Rocky Mountain lodgepole pines that grow in these two southern Idaho mountain ranges — and the red squirrels that don’t.

In his scientific articles, Benkman describes an arms race between the lodgepole and the South Hills crossbill, with the tree evolving thicker scales on its cone and the bird evolving a larger bill to defeat that defense and reach the pine seeds that are its sole food source.

“This arms race has been escalating over the last 5- to 10,000 years,” Benkman said.

What does the red squirrel’s absence have to do with it?

A squirrel eats systematically, removing scales successively from the base of a cone to its distal end. It likes lots of seeds per cone.

Where squirrels are present — throughout most of the range of the Rocky Mountain lodgepole pine — the tree invests in appropriate defense. Selection by red squirrels drives the tree’s cone structure: smaller cones with big bases, tapered tips and only 15 or so seeds.

But a few steps away from his makeshift research station in the South Hills, Benkman picks a cone to show how the lodgepole pine has developed differently here, where crossbills are the primary predators. The cone’s distal end is thick, with heavy scales. Inside might be 50 or 60 seeds.

A crossbill doesn’t care how many seeds are in each cone. To reach a single seed, it must pry apart the scales with its crossed mandibles and extract the seed with its tongue. Smaller-billed birds have a hard time surviving on these South Hills cones.

Here, more than 90 percent of individual lodgepole pine trees are serotinous, with seed release triggered by fire. As the cones weather gradually over years, their bonds weaken and the crossbills gain access to the seeds.

Heat waves, however, disastrously disrupt that food supply.

When summer temperatures exceed 90 degrees in the mountains, mimicking the effect of fire, the resinsealed cones open and shed their seeds prematurely.

That’s great for crossbills temporarily — in July or August — but leaves few seeds available in winter.

A former student of Benkman’s gathered pinecones of various ages to test at what temperatures they open. Benkman wonders: Do some individual lodgepole pines have higher temperature thresholds than others? Could planting those trees support South Hills crossbills longer?

Maybe another century?

“But two centuries from now,” he said, “it’s going to be even hotter.”

••• The South Hills scenario is one of the world’s best examples of an evolutionary arms race, Benkman contends. And one of the

A research team’s box holds crossbills captured briefly for measurements, banding and evaluation.

ASHLEY SMITH, TIMES-NEWS‌

ASHLEY SMITH, TIMES-NEWS‌

Cody Porter, right, and Craig Benkman carefully remove crossbills from mist netting beside a South Hills cabin.

ASHLEY SMITH, TIMES-NEWS‌

Shannon Carvey, right, a field technician for the University of Wyoming, and Cody Porter, a UW graduate student, document crossbill activity in southern Idaho’s South Hills on June 9, 2014. conservation project. best examples of an arms “There’s not much you race causing divergence. can do about it, unless you The resident crossbill can do something about population, he said, is climate change.” genetically distinct, pro••• duces a different flight call On that June 2014 than crossbills elsewhere morning beside a South in the Northwest and only rarely interbreeds with other Hills cabin, Benkman’s call types that move into the research team has two telescopes set up near South Hills yearly.

And he predicts the South the campfire pit. To form survival estimates, they’re Hills crossbill will be extinct watching the trees for crossby the end of the century. bills wearing tiny colored Benkman first captured bands on their legs. and studied South Hills On the plank that serves crossbills in 1997. Before as their research table, a the heat waves of 2003 binder lists the combinahe observed a stable and tions of colored bands abundant crossbill populathat — taken with other tion from year to year. Since visible facthen, their tors — identify decline has individual birds been dramatic. at a distance.

The speOne male cialization that Look Deeper makes this bird See more photos of the with particularly red population South Hills crossbill remarkable researchers in action, plumage and a big bill wears a also makes it attached to this story red-and-white vulnerable. on Magicvalley.com. plastic band The South over a blue one.

Hills crossbill He’s “Captain America,” population plummeted captured often enough that after 2003 solely because of Behl memorized the number decreased adult survival.

A 2011 paper published in on his metal U.S. Fish and Wildlife Service leg band. the Journal of Animal Ecol“He’s used to the drill,” ogy, authored by Benkman says Shannon Carvey, a UW and three other scientists, field technician. details research that pinned For each crossbill lifted the blame on increasing from the mesh-covered spring and annual temperatures and the number of boxes, that drill includes banding — or examination hot, dry days — rather than of existing bands — and scaly-leg mites, West Nile measurements of wing virus or factors that affect length and upper mandible nesting and breeding. depth and length. The team After the extraordinary notes the condition of wing heat of 2003, hot summers and tail feathers, evaluates followed in 2006 and 2007. abdominal fat, checks for Lodgepole pinecones shed parasitic leg mites and looks their seeds, and crossbill at females’ brood patches. numbers suffered.

Blowing at a female’s chest In the early years of Benkman’s South Hills research, to spread her feathers, Behl explains the latter: A patch 70 percent of adult birds of skin on her chest was survived from one year to swollen, or vascularized, the next. After 2003, that while she sat on her eggs. rate dropped to about 45 But her brood patch is wrinpercent. Crossbill density kly now, probably indicating — estimated through point her eggs have hatched. counts at 72 spots scattered Bill depth is particularly throughout the South Hills important because it differ— declined by 80 percent entiates South Hills crossbetween 2003 and 2011.

Both crossbill density and bills from other types. With a small caliper, Behl takes adult survival rose some in multiple bill depth measure2012, he said, but if adult ments for each bird; they’ll survival stays below 70 be averaged later. A nonpercent the population will resident crossbill moving continue to decline. through the South Hills will If the South Hills crossbe carrying fat — another bill gains recognition as a good way to spot call types distinct species, Benkman from elsewhere in the said, it’s likely to become a Northwest, flying hundreds poster child rather than a

of miles between regions with large cone crops.

All of this must happen quickly. The researchers process juveniles first, because they’re more susceptible to stress, then females, so they can return to their nests.

Nathan Hough, a UW undergraduate, alerts Behl to a female with a smooth brooch patch in the next box. She’ll have priority.

The team is happy to discover that one of the male crossbills captured this morning hasn’t been caught since 2009. He’ll increase their survival estimates.

••• Ornithology’s “god squad,” as Benkman calls it, doesn’t yet recognize the South Hills crossbill as a distinct species.

The classification committee of the American Ornithologists’ Union evaluated and declined Benkman’s 2009 paper arguing for species recognition for the South Hills crossbill as Loxia sinesciurus, “without squirrels.” The vote was close.

By 2014 he had rectified the committee’s requests for more specimens and more data, adding 10 South Hills crossbills to the UW collections with call recordings and tissue samples for genetics. His team also analyzed several hundred million sequences of DNA across many North American crossbills.

“We can now show that the South Hills crossbill is genetically distinct from any red crossbill in North America,” Benkman said.

“The evidence now is so compelling, once we have it peer reviewed and published I don’t think that there’s going to be any question about it.”

Field guides show just a red crossbill (Loxia curvirostra) and a white-winged crossbill (Loxia leucoptera).

There’s a lot of variation within the reds, Benkman said, but the South Hills is the most genetically distinct by far. “If there’s any crossbill that deserves recognition at the species level, it’s the South Hills crossbill.”

All 10 call types of red crossbills look roughly the same, apart from variation in size and bill structure.

But sonograms tell the difference.

ASHLEY SMITH, TIMES-NEWS‌

University of Wyoming researchers Shannon Carvey, right, a field technician, Cody Porter and Nate Behl, both graduate students, and evolutionary ecologist Craig W. Benkman log their findings on June 9, 2014, in Idaho’s South Hills.

In a 2012 article on eBird.org, Cornell Lab of Ornithology biologist and sound engineer Matt Young described the flight call of the South Hills crossbill, dubbed Type 9, as a distinctive, dry, “dip-dip.”

Type 2, the Ponderosa pine crossbill ranging continentwide in the U.S., produces a husky, deep “choowp-choowp.” Type 5, the lodgepole pine crossbill of the Western states, makes a twangy “clip-clip.” Both types move through the range of the South Hills crossbill each year.

“But they largely ignore each other. They treat each other as different species,” Benkman said. Females prefer mates of their own call types, and the types interbreed only occasionally.

••• For the 2014 capture team in the South Hills, the moment of each crossbill’s release is vital to determining whether it’s a Type 9, a resident of this mountain range. Cody Porter, a UW graduate student, opens his hands to release a bird while Carvey points a parabola, a

dishlike device fitted with an omnidirectional microphone.

They’re hoping to record a flight call so a sonogram can confirm the type.

“If they don’t call, we don’t know, so we can’t use that data,” Benkman says. “Fortunately, most of them call.”

A year later, Benkman is back in the South Hills with a new team, and every few days he returns phone calls from a peak where he gets cell reception.

He has good news. The 2014 field work, he says, revealed crossbill density rising to reach half of its pre-2003 levels. The bird is coming back, and Benkman is more convinced than ever that the number of hot summer days in the past four years is the key to both decline and recovery.

He predicts adult survival will be strong in the crossbill data he’s collecting this summer, and the team should spot familiar combinations among the colored leg bands.

With luck, Captain America will be back.

Resources • Crossbill researcher Craig W. Benkman’s website, summarizing his points of inquiry: www.uwyo.edu/ benkman • Prairie Falcon Audubon’s tips for where to observe South Hills crossbills: prairiefalconaudubon.org (Use the link in the page’s upper right corner.)

• Comments from the American Ornithologists’ Union committee that narrowly declined species recognition for the South Hills crossbill: checklist. aou.org/nacc/proposals/comments/2009_A_ comments_web.html#2009-A-10 • Biologist and sound engineer Matt Young’s description of various crossbill types’ flight calls: ebird.org/content/ebird/news/recrtype/ • The Idaho Department of Fish and Game’s document designating the South Hills crossbill as critically imperiled: fishandgame.idaho.gov/ifwis/cwcs/ pdf/South%20Hills%20Crossbill.pdf