Эколог Крэйг Бенкман: численность редких кривоглазок Кассии в Айдахо упала с 4,1 до 1,2 тысяч особей

Evolutionary ecologist and ornithologist Craig Benkman, the world’s foremost expert on crossbills, is perhaps best known for discovering the Cassia Crossbills of southern Idaho in 1996 and spending the next 25 years studying them. At home in Timnath, Colorado, he is a University of Wyoming Emeritus Professor and a Fellow of the American Association for the Advancement of Science. For his trailblazing research on bird ecology, evolution, and conservation, he received the E. O. Wilson Naturalist Award from the American Society of Naturalists in 2014 and the William Brewster Memorial Award from the American Ornithological Society in 2019, and he was honored to have a newly described chewing louse, Brueelia benkmani, found on Black-headed Grosbeaks, named after him. His 100+ publications include a 2025 book, Crossbills and Conifers: One Million Years of Adaptation and Coevolution [reviewed in the Apr. 2026 Birding. —Ed.], summing up his life’s work. In this well-informed Birding interview, Benkman enters the fray between crossbills and pine trees, demonstrating how thick beaks and tough cones coevolved through fierce combat. —Noah Strycker, Associate Editor Birding: How did your youthful wanderings south of San Francisco influence your life and career? Craig Benkman: When I was 10, our family moved to near the edge of Crystal Springs Watershed, in San Mateo County, with plenty of hills and valleys to explore. But most memorable were the camping trips my parents took me and my two brothers on every summer, most often to the Sierra Nevada, well east of the Bay Area. In high school, I started reading everything I could about the Sierra, which of course included John Muir’s writings. And I started backpacking. After high school graduation, I spent two months hiking from one end of the Sierra to the other. I brought along my increasingly prized Storer and Usinger’s Sierra Nevada Natural History and used it to learn about some of the birds I began noticing. But I was more interested in the plants and geology, perhaps because those were John Muir’s passion. Birding: When did you set your sights on birds and evolution—switching heroes from John Muir to Charles Darwin? CB: During my first year in college, a family friend suggested I take a three-day “Birds of Yosemite” course. She knew of my budding interest in the natural history of the Sierra, and, being a Bay Area birder, knew about the inspiring instructor—Dave DeSante. I studied my Peterson field guide and the bird section of Sierra Nevada Natural History to prepare. But I didn’t anticipate how thrilling and eye-opening it would be to trek around in familiar habitats with a passionate and knowledgeable guide, seeking birds. The following winter was my first Christmas Bird Count. A kind person must have arranged for me to tag along with the count organizer, Barry Sauppe. The two of us saw scores of bird species, including several regionally notable ones. It became obvious that I had missed out on a lot by not paying attention to birds. Nonetheless, my passion remained with plants and the general natural history of the Sierra. My goal was to become a ranger–naturalist so I could live in Yosemite. But that goal changed after some inspiring courses during my junior and senior years at UC Berkeley. I then decided to go to graduate school to study avian ecology. And as I progressed in graduate school, I increasingly envisioned myself as an evolutionary ecologist. Birding: What got you going with crossbills? CB: When I began graduate school, many topical questions relied on, or were simply best addressed by, studying animals with which one could quantify food intake rates. My master’s thesis on Clark’s Nutcrackers, red squirrels, and limber pine outside of Flagstaff, Arizona, took advantage of the ease with which one could measure seed intake rates. So, I was primed for studying animals like crossbills that rely on cone seeds. Knowing that crossbills were tame and that it would be easy to conduct field-relevant feeding experiments in aviaries, it is perhaps not surprising my interest was sparked by crossbills before I moved to New York to begin my doctoral studies. Birding: How did you discover the Cassia Crossbills of Idaho’s South Hills and Albion Mountains? What makes them so tantalizing? CB: At the time, I was searching for isolated mountain ranges that had lodgepole pine but lacked red squirrels. I was interested in such ranges because my research suggested that, in the absence of red squirrels, Red Crossbills coevolved with lodgepole pine in large but not small mountain ranges. In large ranges where crossbills were abundant, I reasoned that their preferential predation on the more-accessible seeds in smaller cones with thinner scales exerted natural selection on the pine, driving the evolution of increasingly larger cones with thicker scales over successive pine generations. This in turn led to the evolution of even deeper-billed crossbills because they were able to overcome the escalation in seed defenses, resulting in an arms race of increasing crossbill offenses countering increasing seed defenses. Unfortunately, the large-billed and once-abundant Red Crossbills that had resided in the one large mountain range, the Cypress Hills of southwestern Canada, where cones are exceptionally large and thick-scaled, are gone or nearly gone. Red squirrels were introduced there in 1950, resulting in a sharp loss, or perhaps the complete disappearance, of crossbills from that range. Without the crossbills, I could not test for coevolution directly. I was limited to making comparisons of lodgepole pine cones between the Cypress Hills and smaller ranges lacking squirrels. Smaller, squirrel-less ranges were what I expected of the South Hills and Albions based on maps of lodgepole pine. Thus, I was intrigued to find an abundance of Red Crossbills, pines, and large, thick-scaled cones in these two ranges on my way to an ornithological conference in Boise in 1996. I was so convinced that the crossbills there would be different that when I arrived in Boise and had lunch with Bud Tordoff—who had conducted studies on Red Crossbills in the 1950s and 1960s—I told him, “I think I just discovered a new species of crossbill!” That might seem rather brazen. However, at that time, Jeff Groth—whose pioneering research set the stage for my research on the diversity of Red Crossbills—had made a reasoned argument that the different call types of Red Crossbills could represent different or new species. Cassia Crossbills have been a goldmine for me and my students in large part because they are sedentary and abundant, making them reliable for study, unlike most other crossbills. These birds have also provided us with a striking example of coevolution and how the environment—in this case, forest area and red squirrels—influences whether coevolution occurs between pairs of species. Birding: Why did it take so long for the Cassia Crossbill, Idaho’s only endemic bird, to be named to science, only the second nova avis since the early 20th century in the continental U.S. after the Gunnison Sage-Grouse? CB: One reason is that Cassia Crossbills look like Red Crossbills, and they average just slightly larger than the largest call type (Type 2) common in the western U.S. and Canada. Moreover, our initial genetic studies published in 2006 didn’t suggest anything special about the Cassia Crossbill, even though we had found that Cassia Crossbills only rarely interbreed with Red Crossbills. It wasn’t until 2016 that we published more extensive genetic data showing Cassia Crossbills were highly distinctive—and warranted species recognition. An explanation for why other Red Crossbill call types have not diverged genetically was provided by Cody Porter’s subsequent documentation of relatively high levels of hybridization between two Red Crossbill call types (large-billed Type 2 and small-billed Type 5) in the southern Rockies. Birding: How many Cassia Crossbills remain? Why are they vulnerable? CB: They have declined substantially from perhaps only 4,100 individuals in 2016 to about 1,200 individuals in 2025. Part of the decline can be attributed to a fire in 2020 that killed about 20% of the lodgepole pine in their Idaho range. Also contributing was a series of especially hot summer days in 2020 and 2022 that caused many closed cones of Rocky Mountain lodgepole pine to open and shed their seeds prematurely. These lodgepole pine, unlike those in the Sierra, have serotinous cones—cones that remain closed and hold their seeds until heated, historically by fire. Crossbills rely on old, closed cones, from which they can gain access to the seeds as the cones weather gradually. This resource is diminished when the cones open and shed seeds following a series of hot days. After the fire and hot summer days, birders were thrilled to find Cassia Crossbills in the Rockies of north-central Colorado, and a few were reported as far away as the Santa Cruz Mountains just west of where I grew up, indicating that not all of the 3,000 or so that disappeared from the South Hills and Albions died. However, Cassia Crossbills are relatively poorly adapted to cones elsewhere and are unlikely to persist for long—and that seems to be playing out. What is frightening is that fires are increasing in severity, size, and frequency, and we are in for more and even hotter summer days. Birding: Emotionally, how do you feel about the possible impending extinction of the birds you found—and the demise of the lodgepole pine forests in which they live? CB: When I realized that extinction was possible in my lifetime, I was fearful. But now that is overwhelmed by what is happening to so many other species and habitats. We have a working group monitoring Cassia Crossbills with the goal of implementing habitat management to the benefit of the species. Unfortunately, this is but a Band-Aid without a great reduction in carbon emissions. Taking a long view, though, if crossbills—I’m fond of them all—can persist, and if given a future opportunity that includes cooler temperatures, they will diversify and flourish again. Birding: How does your work with crossbills compare to long-term field studies of Galápagos finches (which are, in fact, tanagers)? What do you still want to know? CB: Peter and Rosemary Grant’s long-term Galápagos studies following banded individuals of known pedigrees and genetics provide unparalleled insight. We can’t replicate such studies with crossbills because it would be a Herculean task to follow individuals long-term the way the Grants have on a single small oceanic island. However, we have benefited from the ease at which we can test ideas using captive crossbills. Such experiments are prohibited in the Galápagos. The most glaring gap in our knowledge about crossbills is the history of their lineages. We can fill the gap with genomic studies. This is something we are currently remedying—and something the Grants and their colleagues have excelled at. Birding: What do you want readers to take away from your new book, Crossbills and Conifers? CB: I hope readers gain from learning about the fascinating natural history of crossbills, the astonishing impacts of American red squirrels, and the intimate relationships among crossbills, red squirrels, and conifers. I also want readers to understand how observations in the field inspired hypotheses that we tested with additional observations and often experiments. Finally, I hope readers appreciate the rewards of choosing well. In my case, I picked a species or group of species in which the most fundamental aspect of ecology—the relationship between consumer and resource—could be studied and quantified with the tools at hand. Those tools for me, starting out in 1982, were little more than binoculars, a scope, and a stopwatch. The crossbill–conifer interaction is conveniently marvelous, while providing a foundation that has afforded nearly endless insight into almost anything one can observe crossbills doing. And perhaps this explains why, for me, seeing crossbills now is more delightful than when I first saw them 50 years ago. Birding: Where’s your favorite local patch? What birds do you see? CB: My favorite is a small canyon just west of Fort Collins in the foothills of the Front Range. It has a nice mix of habitats between the bottom and ridgetop with an impressive diversity of breeding birds. Some of my favorite breeders include Virginia’s Warblers, Plumbeous Vireos, Yellow-breasted Chats, Gray Catbirds, and Townsend’s Solitaires. Birding: Is it really an honor having a louse named after you? CB: Absolutely! Every spring, I look forward to squinting through my binoculars when I see my first Black-headed Grosbeak—which are common at my local patch—trying to see something small crawling among the feathers. Noah Strycker has served as Birding magazine Associate Editor since 2006, has conducted the Birding Interview since 2007, and occasionally publishes articles in the magazine. He was 2004 ABA Young Birder of the Year for 14- to 18-year-olds. Noah is an accomplished researcher, writer, photographer, speaker, and guide. His bestselling books include The Thing with Feathers, about the relationships between bird and human behavior, and Birding Without Borders, chronicling his record-breaking 2015 world Big Year of 6,042 species. Called a “Travel Pioneer” by the BBC and “Birdman of Razzmatazz” by Newsweek, Noah also guides in the polar regions for Quark Expeditions and Antarctic Logistics & Expeditions, spreading the joy of birds from pole to pole. Based in Eugene, Oregon, he is often birding farther afield.