An ecologist seeks clues to forest biodiversity
By Lee Sherman | Photo courtesy of Matt Betts
The Persistence of Species
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Birds by BytesGathering acoustic data digitally, he says, has big advantages over the current practice: putting people in the woods to count birds, song by song. Still another technological advance - artificial intelligence - will stream-line the analysis of the electronic data. By employing smart computers that can “learn” to sort ambient noise from distinct species sounds, a team of computer scientists in OSU's Ecosystem Informatics Program is translating the recordings into signals that can be read by computers. Betts and his collaborators hope to push forest ecology to a new level of effi-ciency and sophistication.
“We spend an immense amount of time and money every year surveying birds with technicians,” Betts says. “The overall idea of setting up microphones in the forest was, wouldn't it be cool if we could have cheap, long-term data?”
But Betts's investigations don't stop there. His research program, which has taken him and his graduate students all over Central and North America - from polli-nation experiments in Costa Rica to molecular studies of migratory birds in New Brunswick, Canada - has chalked up a lot of firsts: first to influence warblers' nesting choices with recorded sound. First to put radio transmitters on tropical hummingbirds. First to find conti-nental-scale geographic-dispersal patterns in the chemistry of feathers (see sidebar).
Each study launched from the Betts Forest Landscape Ecology Lab, no matter how far-flung geographi-cally or out-front technologically, has one overarching goal: to isolate the effects of habitat loss, landscape fragmentation and climate change on biodiversity and species persistence (survival over time).
Betts cites a 2010 report from the International Union for the Conser-
A thrush's melody, warbler's trill and sparrow's chip-chip-chip form the musical backdrop for a hike in
the woods. When birds sharing a forest patch all sing at the same time, the cacophony suggests the jumbled chatter of a human social gathering, with competing tones and pitches. In the din, distinguishing among species of warblers, for instance, or tracking individual chickadees is tricky. Scien-tists who study birdsong call this the “cocktail party” problem. Further muddying the forest sound-scape is background noise: rushing wind, splattering rain, crashing branches, foraging animals. Making sense of this audio hodgepodge can test a biologist's mettle.
Matthew Betts is not deterred.The OSU researcher is taking an
innovative approach to recording birdsong in old-growth and second-growth forests. About a dozen microphones recently installed in Oregon's H.J. Andrews Experimental Forest are capturing the calls of bird communities from high in the canopy to low in the understory. A parallel study is under way in New Hampshire's experimental forest, Hubbard Brook.
Concerned with widespread reports of declines in bird popula-tions, Betts is developing new ways to analyze trends in biodiversity. “We're looking at the distribution of 40 or 50 species across the entire elevation gradient at each experi-mental forest,” explains the assistant professor of forest landscape ecology. “We want to know why species live where they do. Why do some species cut off at 1,200 meters yet others persist higher? Is it competi-tion among species? Is it vegetation that's driving that relationship? Is it climatic? It's basic research, but it has big implications for how we predict the effect of climate change on animals.”
» In BriefTHE ISSUE Ecologists need to understand the causes and consequences of population decline in birds and other animal species across forested and other landscapes.
OSU LEADERSHIP Matt Betts is developing new ways to rapidly and efficiently identify birdsong, leading to better knowledge of birds’ movement patterns and persistence. His studies in North and Central America contribute knowledge about stresses on birds stemming from landscape fragmentation, climate change and other factors.
vation of Nature showing that steep declines in populations of birds, mammals, amphibians, plants and invertebrates are continuing across the planet, despite some successful efforts at conservation.
“Habitat loss and fragmentation are known to be the primary cause of species extinctions worldwide,” he notes. “With thousands of species verging on extinction, discovering how animals respond to habitat degradation and disruption is urgent if we hope to reverse the trends.”
By opening all sorts of new windows onto avian behavior - such as using LiDAR (Light Detection and Ranging) technology in a recent habitat study with Woods Hole Research Center - Betts has become a noted innovator in the field of land-scape ecology.
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“Matt's research on the response of bird populations to forest frag-mentation has served as a critical guide for many young and aspiring ecologists,” says Benjamin Zuck-erberg, a research associate with the Citizen Science Program at the Cornell Lab of Ornithology. “Using advanced statistical approaches, he has made significant contributions to the study of ecological thresholds and breeding-site selection in forest birds. Land managers and policy-makers, as well as graduate students, appreciate his ease in communi-cating complex scientific concepts.
“Most importantly,” Zuckerberg concludes, “the results of Matt's research emphasize the role of land-scape ecology in natural resource conservation.”
In the hardwood forests of New Hampshire's White Mountains lives the black-throated blue warbler. Nesting in low-growing shrubs, this abundant warbler is easy to find and count, making it a favorite subject for East Coast ornithologists.
“The black-throated blue warbler is the lab rat of eastern avian demog-raphy,” jokes Betts, who first studied the species as a post-doctoral fellow at Dartmouth College.
These handy birds have given Betts surprising new insights into the purposes and powers of song. Wondering how birds choose nesting sites, Betts and a team of researchers from Wellesley College and from Queen's University and Trent Univer-sity in Ontario, Canada, recently ran an experiment to see whether, in essence, they could “trick” the warblers into picking poor places by making them think other warblers favored those spots. The scientists played electronic warbler songs at 54 White Mountain locations - scrubby areas with scant cover that warblers normally would bypass. But having heard their species' songs broadcast as they flew over in the fall, many returning warblers chose the sub-par nesting sites the following spring. In fact, more than 80 percent of first-
time breeding males settled in the bad habitat, Betts and his colleagues reported in the Proceedings of the Royal Society B: Biological Sciences.
“We were very surprised,” Betts told Science magazine's blog, Scien-ceNOW. “It was almost as if we'd attracted a spotted owl (secretive old-growth dwellers) to a parking lot.”
Taking cues from fellow warblers is a shortcut to scoping out optimal breeding grounds, Betts explains. It's a behavior that can aid the species' adaptability to rapidly changing landscapes.
“The approach this bird uses can be very efficient in allowing individuals to find new habitat quickly when old
habitat has been lost or degraded,” he says. “We're developing a library of species that use this nest-site selection strategy, which may make them less sensitive to environmental changes than species that are poor at finding new habitat.”
Flight Paths The green hermit hummingbird of Central America weighs over three-tenths of an ounce - approxi-mately the heft of a good-sized chickadee. By hummingbird stan-dards, that's huge. (In contrast, the Pacific Northwest's ubiquitous rufous hummingbird tips the scale at just one-tenth of an ounce.) The green hermit's heavyweight status makes it a prime candidate for tracking by radio transmitter because although
the transmitter weighs less than one-hundredth of an ounce, it's too heavy for the tiny rufous to carry on its back.
Betts and Ph.D. student Adam Hadley wanted to investigate hummingbirds' travels through the rainforests of Costa Rica to help explain why pollination levels around the world appear to be drop-ping. In particular, they wondered how fragmented forests - patches of trees left stranded amidst areas cleared for roads, crops or timber - affect the flight patterns of the iridescent, curved-billed pollinators.
“Recently, people have started real-izing that landscape configuration, especially fragmentation - how habitat is distributed - can be quite important for some species,” Betts explains.
So in the winter of 2008, the researchers glued miniature trans-mitters to 19 green hermits with false-eyelash adhesive and then monitored the birds' movements for several weeks until new feather growth made the transmitters fall off. In the journal Biology Letters, the scientists reported that the birds adhered closely to the shape of the landscape, clinging to treed areas while avoiding open patches devoid of cover - even when that meant flying longer distances. Not only are the longer distances poten-tial stressors for the birds, but the avoided patches may miss being pollinated, thus losing plant diver-sity over time.
“We don't yet know for sure if pollen dynamics are being disrupted by forest fragmentation, but we strongly think so,” says Betts. “Our hummingbird research suggests that maintaining riparian corridors of forest between patches could be quite important for pollination dynamics.”
Heroic TriumvirateBetts' heroes - three titans of biology, Edward O. Wilson, Ernst Mayr and Paul Ehrlich - all began their careers studying animals (ants, birds and butterflies, respectively). But over
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time, they extended their inquiries to such sweeping scientific ques-tions as the mechanisms of evolu-tion, Earth's ecological thresholds and the origins of human nature. All became active in the political sphere, advocating on behalf of the planet's long-term survival.
While not presuming to share the lofty status of these science super-stars, Betts imagines his career taking a similar beyond-the-lab trajectory. For him, however, public-policy work will be a homecoming of sorts. As an undergraduate - moti-vated by his childhood wanderings among the woods of New Bruns-wick - he aspired to conserve the forests where so many mysteries were secreted. So he studied political science. He soon realized, however, that if he hoped to influence policy, he first needed grounding in the fine and complex details of ecosystems - in what he calls the “micro” sphere of forest management and conser-vation. So he went back to study biology and ecology.
Still, it's at the policy level where discoveries give rise to action. Betts sees himself looping back more strongly to the macro sphere as time goes by. “It can get very frustrating doing science when you're just pumping out scientific papers and nobody's paying any attention to it,” says Betts, who serves as OSU's repre-sentative on Oregon's State Forest Advisory Committee, which provides input to the Oregon Department of Forestry on forest management issues. “That's what drew me to the College of Forestry, actually. There's this potential link between basic research and applied work, and then translation into some kind of action.”
If science can, for instance, reveal how fragmentation affects animals - as opposed to simple habitat loss - the findings can guide decision-makers in tangible ways.
“We have the power to design landscapes in different ways,” Betts notes. “Losing the same amount of habitat, developers or foresters could
decide to leave wildlife corridors, or they could decide to leave a single big patch instead of making four little ones. It becomes pretty important when thinking about the persistence of species.”
Still, he says, doing science - even stopping for a minute to enjoy a warbler's stirring call - can be a
satisfying refuge from the conten-tious political arena.
“Basic research is nice because it doesn't depend on people that much,” he admits. “So if I'm depressed about the rate at which my findings get turned into policy, at least I'm finding out some interesting things about nature. That's good in itself.”
Volunteers help teach computers to ID birds by song
RECORDING THE SUBTLE SYLLABLES, NOTES and motifs that distinguish one bird species from another requires some pretty sophisticated gear. But for OSU researchers, collecting audio data in an old-growth forest last summer was a walk in the park compared with analyzing it. “It's a lot of data," reports Jed Irvine, a faculty research assistant in the OSU Bioacoustics and Machine Learning group.
Confronted with a terabyte of digital sound from the H.J. Andrews Experimental Forest, Irvine and a team of students in the College of Engineering are building a website that will let them borrow the ears of experienced birders to identify avian singers. These IDs will then be used to “teach" computers how to distinguish a robin from a Swainson's thrush or a tree swallow for a study being led by forest ecologist Matt Betts.
The terabyte gets its name from the Greek word tera, meaning “monster." The etymology is apt. Trying to grasp the size of a terabyte - a trillion bytes of computer data - is like trying to wrap your mind around the number of water drops in Crater Lake or sand grains on Cannon Beach. Besides their monstrous size, these audio files may contain all sorts of extra sounds, from streams to airplanes to distant highway traffic. Also compli-cating the task of automatically recognizing bird sounds is the fact that birds can sing in regional “dialects," and some even mimic other species.
Where the Birds Are“The bioacoustic team is developing software that will automatically identify bird spe-cies - perhaps even individual birds - so that we can assess population distribution on an ongoing basis," Irvine explains. Then, without a hint of irony, he adds, “It's a lofty idea."
An amateur birder himself, Irvine came up with the idea of creating a website that would allow birders to upload bird images and audio for annotation and discussion. The bioacoustics and machine learning problem being worked on by professors Xiaoli Fern and Raviv Raich was a perfect task for the Web, Irvine says. Once the website was ready for the first round of user testing, he asked local birders to test-drive the site by listening to sound clips online and then posting species IDs for each clip. By the end of June, he had gotten 85 identifications from about a dozen volunteers.
In the next phase of website development, he hopes to make the experience of using the site as close to the experience of “birding by ear" as possible. Each online session will be designed as a “birding trip" into the forest, where volunteer birders can employ their knowledge of birdsong to further the goals of science.
“The next iteration will be more interesting," says Irvine, who started birding with his dad as a kid in New Jersey. “We want to make the site addictively fun for birders, so that we can get as many bird sound snippets identified as possible."
Visit the site at http://web.engr.oregonstate.edu/bird
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