Science editor Gus Axelson is just back from a tour of eastern Hungary sponsored by Swarovski Optik. (Look for his story about bird conservation in Hungary to appear in a future issue of Living Bird.) As Gus returned to the world of American Redstarts and other brilliant warblers, he turned his attention to a more basic question: what’s with the drabness of the European warblers? Here’s Gus:

I suppose one could say that brownish European warblers are no different than our sparrows—differentiating a Savannah from a Song from a Lincoln’s sparrow can be tricky if you rely on field marks alone. But c’mon, these are WARBLERS. Some of the most cheery, dazzling, brilliant participants in spring’s migratory parade!

Europeans have a different opinion. Dale Forbes, an Austrian, argued on 10,000 Birds last year that “real” warblers are brown, and our warblers are little more than “silly canaries.”  (Although it took only one wood-warbler extravaganza at Magee Marsh this past May for Dale to reconsider his position).

Personal opinions aside, there’s an interesting evolutionary question here. Warblers on either side of the Atlantic aren’t making a fashion choice in their plumage (“Should I wear yellow or brown before Memorial Day?”). Is there some kind of competitive advantage for warblers being brown in Europe and colorful in North America?  I posed that question to Irby Lovette, director of the Fuller Evolutionary Biology program here at the Cornell Lab (and leader of a project that mapped the wood-warbler tree of life).

Irby quickly pointed out that though both groups are called “warblers,” they’re not particularly closely related—so you wouldn’t necessarily expect them to sport similar plumages. Europe’s warblers are all in a superfamily, Sylvoidea, while North America’s all belong to the family Parulidae. That’s why your field guide places the few Old World warblers that show up in North America (like the Arctic Warbler) near the kinglets, and far removed from “our” warblers.

Taxonomic worries aside, Irby was still willing to offer an explanation:

“So scientifically we have to just consider why some birds are drab and others are brightly colored. The reason our wood-warblers are more colorful has to do with various forms of sexual selection. Our male warblers use their bright plumage as symbols of status. Consider the American Redstart. First-year males are more drab, but adult males are brightly colored, and they get the best territories. Colorful male plumage is also beneficial in attracting females. And when you look at our female warblers, they tend to be more drab.

“So, why are European warblers drab? Well, they accomplish the same thing, males compete with other males and attract females, but they do it through their songs instead. They tend to be prolific songsters. So European warblers just chose a different type of communication.”

(And indeed, the Euro birders on the trip bragged their warblers were superior singers.)

Even though I prefer my warblers to be bright and cheery, I will concede that the subtleties of European warblers necessitates better technical ID skills. On my Hungary trip, the British contingent of birders were adept at using setting, posture, behavior, and song in identifying birds, and they relied on field marks only as supporting evidence. That’s also the gist of our Inside Birding video tutorials, in case you’re interested in brushing up on your own skills.

For me, one final anecdote from the trip sums up the debate. After birding in Hungary’s Bükk National Park one day (where I racked up Eurasian Treecreeper, Marsh Tit, Rock Bunting, and Hawfinch), I sat down for a cold Soprani beer with the European birders. A Swede named Per Göran Bentz told me he had a photo of his favorite warbler on his credit card. He opened up his wallet, took out the card, and showed me a striking image of a Blackburnian Warbler.

• Do you agree or disagree? Read the second post in this series: Counterpoint: 7 Ways European Warblers Outperform American Warblers

(Images via Birdshare: European warblers at left: Arctic Warbler by Bill Thompson; Common Chiffchaff by Etienne Littlefair; North American warblers at right: Blackburnian Warbler by Danny Bales; Prothonotary Warbler by A wing and a prayer.)

Red Crossbills range all over North America’s western mountains and northern forests, filling the air with their brief, metallic chips and attacking pine, fir, and hemlock cones with their unique bills. But there’s a growing realization that this species consists of a whole group of distinct types—some of them possibly even full species. Plumages don’t differ much from one crossbill type to another, but the evidence lies in subtle differences among those chip notes and crossed bills.

Last week was the annual meeting of the American Ornithologists’ Union, where hundreds of scientists get together and talk about pretty much any topic of study that has ever been brushed by a feather. The University of Wyoming’s Craig Benkman summarized his career’s work studying Red Crossbills. Wesley Hochachka, assistant director of Bird Population Studies at the Cornell Lab, was on hand and sent us this account. Here’s Wes:

The world is full of amazing “radiations” of birds—that’s what evolutionary biologists call groups of closely related species that have evolved amazing diversities of plumage, size, bill shapes, and habitat requirements. The Darwin’s finches of the Galapagos Islands and the many species of Hawaiian honeycreepers are two of the most famous examples. So, why would a scientist choose to study a radiation of birds that all look very similar—all subtly hued and devoted to a single food, conifer cones?

Craig Benkman answered that question convincingly in his plenary talk on crossbills at this year’s American Ornithologists’ Union meeting. Craig has spent decades studying crossbills, and having known him for many years I think that he probably lives, thinks, and dreams crossbills (and it wouldn’t surprise me if he sprinkles pine nuts on his breakfast cereal too). Right now, we recognize two species of crossbills in North America—but Craig’s work shows ecological grounds for the possibility that there are many species of crossbills coexisting right under our noses.

Crossbills are finches whose beaks, as their name suggests, cross at the tip. This seeming malformation is actually a wonderful adaptation that allows the birds to access seeds hidden between the scales of conifer cones, seeds that are inaccessible to other species of birds. The curved bills, coupled with crossbills’ ability to shift their lower mandibles sideways, allow the birds to pry open conifer cones and extract the seeds with their tongues. If that’s hard to envision, here’s a video that explains how a related species, White-winged Crossbills, do it).

Over his career, Craig has uncovered that among Red Crossbills, this remarkable feeding adaptation is even more finely specialized. Several different types of crossbills (they may be species, or near-species) each specialize on a different species of conifer—because different kinds of trees have differently sized cones and seeds. The sizes of the crossbills’ beaks closely match the cones they feed on and can efficiently pry apart the cone scales to get at the seed inside. Even the part of the beak used to crack open the conifer seeds, once they are extracted, is sized appropriately.

In western North America, where conifers come in widely varying sizes and shapes (such as ponderosa pines, lodgepole pines, Douglas-firs, and western hemlocks), this has led to the existence of multiple “types” of Red Crossbills. Each has not only a differently sized beak but also a distinctive call note that can be used—by birds or bird watchers—to tell the types apart. These types may or may not be full species, but they use different food sources, usually live in different geographic regions, and choose members of their own type with which to mate. So they in many ways behave like isolated species. The AOU’s North American Classification Committee periodically reassesses the evidence to decide whether to grant them full species status.

Another theme to emerge from Craig’s talk was that it’s not just crossbills that adapt to cones—the cones adapt to crossbills and other seed predators, such as squirrels. Red squirrels can outcompete crossbills for conifer seeds, because the squirrels preemptively cut the cones off trees and store them underground. In places with lots of red squirrels, the types of defensive structures on cones appear aimed to dissuade squirrels and not crossbills.

Even more dramatic evidence of the competition between squirrels and crossbills comes from two “islands” in Canada: the Cypress Hills, in Alberta and Saskatchewan, and forests on Newfoundland. The latter is a true island, and the former a biological island: forested slopes surrounded by prairies. Both of these “islands” held distinct and unique types of Red Crossbills, and before human intervention neither “island” was occupied by squirrels. Now, both of these crossbill types are either extinct or approaching extinction due to the introduction of red squirrels.

While crossbills may not be the most dramatic of birds to see or hear, Craig’s story provides a fascinating look into the ways in which animals and their food supplies can be tightly, and delicately, tied to each other.

Read more about the many types of Red Crossbills in this Living Bird article from 2010.

(Image: Red Crossbill photographed in British Columbia by Mike Wisnicki, via Birdshare)

It’s time for another annual meeting of the American Ornithologists’ Union. Just like last year in Philadelphia and 2009 in  Portland, we’ll be bringing you stories from the floor of the meeting, where hundreds of ornithologists have gathered for four days of intense science.

First up is Living Bird editor Tim Gallagher to report on Monday’s plenary talk, given by University of Montana’s Ken Dial. Over the past decade, Dial and his collaborators have proposed a surprising new theory about how birds first began to fly. And with a wicked snowstorm shutting down air travel back East, the evolution of flight seemed perhaps the perfect topic. Read Tim’s account after the jump.

The 128th annual meeting of the American Ornithologists’ Union (which this year is a joint meeting with the Cooper Ornithological Society and the Society of Canadian Ornithologists) got off to a slightly bumpy start Monday morning at 8:00 a.m. It seems the first plenary speaker, Scott Derrickson of the Smithsonian’s National Zoological Park, got stuck in the snowstorm blanketing Washington, D.C., and couldn’t make it to San Diego last night.

Not to be stymied by a little thing like inclement weather, the AOU leadership pivoted instantly and asked Kenneth P. Dial of the University of Montana to present his scheduled Tuesday morning plenary 24 hours early.

Now, for many people, having to deliver a talk a day early can be horrendous. There you are, expecting to have all this extra time to prepare and practice, but instead you just have to get up and go at a moment’s notice. Fortunately, Dial was more than up to the challenge. With his exuberant personality, a sense of humor and comic timing as well honed as most stand-up comedians, and a boundless passion for his topic of study, he presented his hypotheses on the evolution of flight in birds. In the process, he took on 150 years of entrenched dogma.

Dial began his talk by apologizing for not having time to dress up and get his hair done for the talk. (He was clad in blue jeans and a sweater and has a shaved head.) Then he launched into his talk, exploring whether bird flight had an arboreal (trees-down) or a terrestrial (ground-up) origin. The long-accepted belief has been that birds originated in the trees, but Dial takes on this idea, presenting a compelling array of data to support his view that flight originated from the ground up

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Others have pointed out that some feathered dinosaurs had tiny wings, much too small to be used in flight. Why is that? Were they just useless appendages? Or did they help vulnerable young dinosaurs to scramble up inclines to escape predators.

Dial has looked at numerous species of fledgling birds—tinamous, megapodes, brush-turkeys, chukars, swifts, pigeons, owls, and more—and has documented this kind of “wing-assisted incline running” in all of them. The young birds use their stubby wings to help them gain traction as they run up the side of a tree or other incline and also to flutter back down to the ground safely. Could this have been how flight originated—at first as a way for a fledgling to escape predators?

At the University of Montana’s Flight Laboratory, Dial uses high-speed x-rays to explore flight in adult birds as well as the mechanisms by which fledglings scramble up inclines—some at a 90-degree angle. (You can watch slow-motion videos of birds flying in wind tunnels.) One could easily imagine an Archaeopteryx making a similar ascent before diving off the end of a branch and gliding downward again.

Ken Dial ended his talk with a plea to ornithologists to always be open to new ideas in their research and especially in their teaching of young scientists. Whether or not you agree with his hypotheses (and he perhaps left the audience with more questions than answers), this felt like the perfect kind of rousing, fascinating discussion to get a meeting going. You could see it in the eyes of the students as they left the ballroom and walked downstairs for the coffee break.

(Image: AOU 2010 logo by David Stamp)