In a current guide, Benkman displays on his analysis profession learning the evolutionary interaction between crossbills and the cone-bearing timber the place they feed.
From the Autumn 2025 situation of Dwelling Hen journal. Subscribe now.
The remainder of Craig Benkman’s life started on a snowy late-winter morning in 1982. Because the first-year graduate pupil ready to attend a seminar on ecology on the State College of New York at Albany, a classmate burst into his workplace with an pressing message: “Craig, Craig! There are crossbills coming to the bottom outdoors!”
Benkman’s coronary heart leapt. For months, he had searched across the Hudson Valley for the unusual crimson finches, pondering they might be an ideal examine topic for his dissertation. However thus far, he’d had no luck discovering any crossbills.
When he proposed learning the birds for his PhD, he knew it wouldn’t be straightforward. Pink Crossbills and White-winged Crossbills, so named for the overlapping suggestions of their payments, are notoriously nomadic, wandering huge distances throughout North America’s distant evergreen forests in quest of their solely meals supply: the seeds of conifer timber, reminiscent of spruces and firs and pines.
Not like different birds that reliably nest in the identical place 12 months after 12 months, crossbills will breed wherever and at any time—even within the lifeless of winter—as long as they discover an considerable provide of conifer seeds. All of the whereas, they continue to be excessive within the treetops, making crossbills notoriously tough topics for ornithological analysis.
One college member on Benkman’s dissertation committee merely laughed on the considered learning the birds.
“I form of obtained discouraged,” Benkman says. “I virtually stop.”
Nonetheless, Benkman was satisfied that crossbills had potential. That very same dependence on a single, unreliable meals supply that made the finches so difficult to check additionally raised a bunch of fascinating inquiries to discover: How had the birds tailored to the challenges of accessing conifer seeds? Why did totally different crossbills have totally different invoice shapes?
So when Benkman’s classmate knowledgeable him of the crossbill flock on campus, he didn’t hesitate.
“A bunch of us stated, ‘No class immediately!’” remembers Benkman. By the top of the day, Benkman had netted about 10 Pink Crossbills—greater than sufficient to probe how the curious finches carve into conifer cones.
“I assumed, ‘Properly, I suppose I’m going to check crossbills!’” he remembers.
And so he did—for the subsequent 40 years.
Over a embellished analysis profession that has netted him honors from the American Society of Naturalists and American Ornithological Society, Benkman’s influential work expanded not solely how ornithologists perceive crossbills, but additionally how evolutionary biologists perceive the connection between species and their environments. He chronicles his life’s work learning the finches of the Loxia genus and extra in his thorough and wide-ranging guide Crossbills and Conifers: One Million Years of Adaptation and Coevolution, revealed in summer time 2025 by Pelagic Publishing.
“[The book] touches on so many alternative dimensions of what we consider when it comes to avian biology and ecology and evolution,” says Irby Lovette, director of the Cornell Lab of Ornithology’s Middle for Biodiversity Research. Lovette says studying about Benkman’s work on crossbills is nearly a crash course in ornithology. “It’s like all the pieces in a single fowl.”
Beginning with that one snowy day in Albany, Benkman made his life’s work out of chasing crossbills from New England to Canada’s Maritime Provinces and out west to the Rocky Mountains and remoted South Hills of Idaho. Alongside the best way, he developed fascinating insights into the relationships between birds and their habitats, challenged conventional notions about how fowl species and their meals sources evolve, and even found a new species of crossbill.
Uncovering the Crossbill’s Seed-Consuming Secrets and techniques
After Benkman captured his first crossbills, he shuttled them to a makeshift aviary on campus. Within the wild, it could be not possible to look at crossbills forage on the degree of element obligatory to grasp how they effectively slip seeds from cones. However from behind a one-way mirror within the aviary, Benkman had an unprecedented close-up to the subtleties of feeding crossbills.
“The birds are so tame in captivity,” he says. “As soon as you place them in a cage, they’ll begin feeding on cones inside a few minutes.”
He spent tons of of hours observing the Pink Crossbills forage on amply supplied pine cones—watching and taking notes as they contorted and flipped each which option to extract and husk seeds in seconds—earlier than releasing them again into the wild.
“Greater than as soon as, I needed to catch myself from clapping in admiration at what these feeding birds may accomplish,” Benkman writes in his guide.
Benkman’s front-row seat in a lab aviary was good for understanding the main points of crossbill feeding.
However to grasp how the birds work together with their surroundings, he wanted to enterprise out into the huge boreal forests that crossbills name dwelling. He scoured the outer reaches of Ontario, Quebec, and New England for flocks of White-winged and Pink Crossbills, even snowboarding down snowy forest roads on frigid midwinter days.
“I’ve indelible recollections of beautiful crimson, black, and white male White-winged Crossbills singing whereas flying over snow-ladened spruce when temperatures hovered at –20°F,” Benkman writes.
As soon as he discovered crossbills within the wild, Benkman vigilantly recorded as a lot data as he may about their habitat and conduct: what timber had been round, what number of cones they carried, what the crossbills ate, what number of seeds they consumed. He additionally grew to become adept at noticing the formation of tiny conelets within the spring, an indication of a crossbill-attracting cone crop that he may examine the subsequent 12 months.
Upon incomes his doctorate in ecology in 1985, Benkman authored a collection of papers that enormously enriched the scientific literature on crossbills. Throughout seven research, he defined how crossbills use their elongated payments to pry open powerful cone scales; found {that a} crossbill’s crossed invoice was important for consuming massive quantities of conifer seeds, however a hindrance to consuming other forms of seeds; and described how the small invoice of the White-winged Crossbill makes it nicely fitted to exploiting tiny spruce and tamarack cones, whereas the bigger payments on Pink Crossbills can extra simply break into hefty pine cones.
Alongside the best way, the once-mysterious birds grew to become extra acquainted to Benkman, each scientifically and personally. He started to really feel as if he knew the crossbills in addition to they knew themselves—their personalities, tendencies, and whims.
“It’s form of like bonding with a canine,” he says. “Having the ability to really feel virtually at one with an organism is a wonderful factor.”
Taking place Upon An Evolutionary Classroom within the Idaho Hills
In subsequent stints as a postdoctoral fellow at Princeton College and the College of British Columbia, Benkman continued to construct his bond with crossbills as he explored how they adapt to their surroundings. However after accepting a school place at New Mexico State College, he discovered himself surrounded by desert, removed from his acquainted finches.
“I wasn’t satisfied I used to be going to proceed to check crossbills,” he says. “I began interested by learning lizard communities.”
He nonetheless had time to discover one final speculation, although. Benkman suspected that since crossbills harvest tens of millions of conifer seeds yearly, the conifer timber would possibly in flip be adapting to raised defend their seeds from predators. He puzzled a couple of coevolutionary arms race—two species, a fowl and a tree, changing into more and more intertwined as they adapt in response to 1 one other.
However learning his hunch can be sophisticated by squirrels. Throughout the Pink Crossbill’s vary, crimson squirrels are seemingly in all places, and they’re voracious cone predators. Benkman suspected that within the presence of squirrels, any crossbill-induced variations would seemingly be few and much between.
To look at conifer timber armed with defenses particularly in opposition to crossbills, Benkman would want to discover a swath of forest free from squirrels. He pored over crimson squirrel vary maps and native fowl surveys for clues.
After a couple of failed efforts, a convention in Boise in 1996 gave Benkman an opportunity to go to one other potential web site: the South Hills, a small island of mountains rising from southern Idaho’s Nice Basin.
It was a protracted shot.
“No ornithologist had ever instructed something particular in regards to the crossbills within the South Hills,” Benkman writes. However upon arriving within the forest, he was instantly struck by the abundance of crossbills that appeared like Reds, with massive payments and unusual calls. The crossbills fed with glee atop lodgepole pines, and there was not a squirrel in sight.
“It was no understatement that I used to be euphoric,” Benkman writes. He had discovered a residing evolutionary laboratory. And if the South Hill crossbills had been as totally different as he suspected, he might have found a brand new species.
Over the a long time that adopted, Benkman—and a bevy of graduate college students from New Mexico State and the College of Wyoming, the place Benkman was employed in 2004—examined the South Hills and their crossbills from each angle. Approaches ranged from the excessive tech—like sequencing parts of crossbill DNA—to the artistic, together with snipping cones from unreachable branches utilizing 30-foot-long clippers, and even utilizing dental gear to make molds of the insides of the birds’ payments.
At each flip, the analysis confirmed Benkman’s preliminary suspicions. The cones within the South Hills had been unusually massive and had unusually thick scales at their outer ends, the place crossbills want to feed—a transparent signal of tree evolution pushed by crossbills. Accordingly, the native South Hills crossbills had abnormally massive payments and, in contrast to typical roving crossbill conduct, tended to stay across the mountains year-round. When birds from different crossbill lineages wandered in, they usually moved on rapidly after discovering the hefty lodgepole pine cones that native birds had been much better at harvesting.
Benkman and his collaborators found that the interloping crossbills hardly ever bred with the Idaho natives, making the South Hills birds increasingly distinct as they continued to adapt to their very own distinctive surroundings and meals. The native crossbills even had totally different vocalizations than Pink Crossbills elsewhere within the West.
These findings indicated to Benkman that the finch was evolving into a brand new species. The proposed title for the brand new fowl was Cassia Crossbill, after the county in Idaho the place it resides; its Latin species title, sinesciurus, means “with out squirrels.”
In 2017, the American Ornithological Society’s North American Classification Committee accepted Benkman’s proposal. After a profession stuffed with discovery, he had his crowning achievement—not that Benkman is one to boast.
“I’ve been privileged simply to form of bumble alongside and reply questions that, ‘gosh, this appears attention-grabbing—hopefully different individuals might be ,’” he says. “In some instances, different individuals had been .”
With Benkman’s discovery of the Cassia Crossbill, the once-overlooked South Hills space grew to become a major birding vacation spot, with birders keen so as to add a possible new species for his or her life lists. A current examine by an economist at Mount Holyoke Faculty documented that wildlife tourism within the area has boomed because the Cassia Crossbill was designated its personal species, with the annual variety of birder visits almost doubling during the last decade.
“With my birder hat on, I’ve made certain that I’ve seen them,” says Lovette, who deliberate a visit to Cassia County particularly to see Benkman’s birds.
Evolutionary biologists had been additionally fascinated by the methods Cassia Crossbills have formed their surroundings.
“As a scientist, I adore it as a result of it’s a bit of little bit of a window into how species kind,” Lovette says. “It’s form of the textbook instance of coevolution between birds and their diets.”
In actual fact, it’s too good of a textbook instance. When Lovette edited the Cornell Lab’s Handbook of Hen Biology ornithology textbook, he needed to ask contributing authors to keep away from utilizing so many crossbill examples.
“[The crossbill research] isn’t just about dietary ecology or foraging—it’s additionally about evolution and about contact calls and coevolution and neighborhood ecology,” Lovette says.
Benkman retired as a College of Wyoming college member in 2022. However even after 4 a long time spent chasing and learning crossbills, he’s not accomplished exploring the Loxia finches. Familiarity has not bred contempt—removed from it.
“Take an astronomer: The extra they find out about area, the extra they marvel at it after they search for,” Benkman says.
Subsequent summer time, he might be ready in his dwelling close to Fort Collins, Colorado, for the Pink Crossbills to return to the forests close by. The uncertainty of his youthful self is gone. He is aware of the crossbills will come again.
“I can’t wait,” he says. “They bring about me great pleasure each time I see them.”
Concerning the Creator
Benjamin Hack is a contract author based mostly in Arlington, Virginia. A former pupil editorial assistant at Dwelling Hen via the Cornell Lab of Ornithology’s Science Communications Fund (made potential with assist from Jay Branegan [Cornell ‘72] and Stefania Pittaluga), Hack has additionally written for Audubon and Smithsonian magazines.
