Birds’ Feathers Reveal Their Winter Diet

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A freshly molted Bobolink. Photo credit: R.M. Jensen

Influences outside the breeding season can matter a lot for the population health of migratory birds, but it’s tough to track what happens once species scatter across South America for the winter months. A study from The Condor: Ornithological Applications tries a new approach for determining what declining migratory grassland birds called Bobolinks eat after they head south for the winter—analyzing the carbon compounds in their plumage, which are determined by the types of plants the birds consume while growing their feathers during their winter molt.

Thanks to a quirk of photosynthesis, rice contains a different ratio of carbon isotopes than most of the native grasses in South America where Bobolinks winter. Rosalind Renfrew of the Vermont Center for Ecostudies and her colleagues took advantage of this, collecting feather samples from wintering Bobolinks in a rice-producing region and a grassland region and from breeding Bobolinks in North America. When they analyzed the feathers’ isotopes ratios, the results from South America confirmed that isotopes in Bobolinks’ feathers reflected the differences in their diets between regions with and without rice production. The samples taken in North America showed that the winter diet of most individuals was weighted more toward non-rice material, but that rice consumption was highest late in the winter, when rice is nearing harvest and the birds are preparing for their northbound migration.

Rice could be beneficial by providing the birds with needed calories as they prepare for their journey north, but it could also increase Bobolinks’ exposure to pesticides and threats from farmers who see them as pests. According to Renfrew and her colleagues, maintaining native grasslands, encouraging integrated pest management programs to reduce toxic pesticide applications, and compensating farmers for crops lost to feeding birds all would be helpful.

“The time spent coordinating the field work for this study may well have been greater than the time spent collecting the data,” says Renfrew. “It was truly a team effort, and the assistance we received from our partners was absolutely essential, especially in South America. Aves Argentinas and the Museo de Historia Natural de Noel Kempff Mercado provided priceless logistical support, and this study could not have happened without them. Some of the same partners have provided input on a Bobolink Conservation Plan that lays out actions to address threats to grassland birds in North and South America, based on results from this and other studies.”

“As Bobolink populations continue to decline, Renfrew and her colleagues use state-of-the-art isotope analysis techniques to assess the Bobolink’s diet on its South American wintering grounds,” according to John McCracken of Bird Studies Canada, an expert on grassland bird conservation who was not involved with the study. “The authors conclude that rice may have negative effects on Bobolinks, owing to its relatively low nutritional quality and from exposure to insecticides.”

Winter diet of Bobolink, a long-distance migratory grassland bird, inferred from feather isotopes is available at

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society, which merged with the American Ornithologists’ Union in 2016 to become the American Ornithological Society.

2016 Journal Impact Factors Released

The 2016 impact factors for peer-reviewed journals were released last week, and both journals published by the American Ornithological Society saw a boost in their numbers—The Condor is up to 2.654 from 1.427 and is now #1 of the 24 ornithology journals ranked, and The Auk is up to 2.096 from 1.871 (ranking #4). This means that the American Ornithological Society now publishes half of the top four ornithology journals in the world.

Impact factors are calculated based on the number of citations received in a year by articles published in a journal during the two preceding years and are considered to be an important measure of a journal’s prominence in its field. The AOS publications team wants to thank all of our Associate Editors, authors, and reviewers, as well as everyone who reads and cites The Auk and The Condor!


Radar Reveals Steep Declines in Kauai’s Seabird Populations

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A Newell’s Shearwater chick in a burrow. Photo credit: A. Raine

The island of Kauai is home to two endangered seabirds, the Hawaiian Petrel and the Newell’s Shearwater. Monitoring these birds, which are nocturnal and nest in hard-to-access areas, is challenging, but observing the movements of birds via radar offers a solution. A new study from The Condor: Ornithological Applications takes a fresh look at two decades of radar data—and comes to worrying conclusions about the status of both species.

To assess the population trends and distribution of the birds in recent decades, André Raine of the Kauai Endangered Seabird Recovery Project and his colleagues examined past and contemporary radar surveys as well as data on the numbers of shearwater fledglings rescued after being attracted to artificial lights. Their results shows continuing population declines in both species over the last twenty years—a 78% reduction in radar detections for Hawaiian Petrels and a 94% reduction for Newell’s Shearwaters, with the shearwater decline mirrored in decreasing numbers of recovered fledglings over time.

For shearwaters, this is consistent with previously published work, but past analyses of petrel radar data suggested their population was stable or potentially increasing. The researchers attribute the difference to the fact that for this new study, they carefully standardized the data based on sunset times, which ensured that the time periods (and thus bird movement periods) under consideration remained constant from the beginning to the end of the survey period. They believe that the steep declines may have commenced in earnest in the aftermath of Hurricane Iniki in 1992, which led to permanent ecological changes such as the opening of new routes for invasion by exotic predators and plants, as well as significant infrastructure changes across the island.

“These seabirds face a wide range of threats,” says Raine. “Conservation effort needs to be focused on reducing power line collisions, fall-out related to artificial lights, the control of introduced predators, and the overall protection of their breeding habitats. Many of these efforts are now underway on Kauai, and I am hopeful that these will continue and expand over the next few years. Ultimately, the conservation of the breeding grounds of endangered seabirds on Kauai is actually the conservation of our native forests and watersheds, with far-reaching benefits for other native plants and birds that rely on these habitats, as well as—ultimately—ourselves.”

“It is important to publish this information so that everyone can better understand the severity of the declines in these species and the threats they face,” agrees Pacific Rim Conservation’s Eric VanderWerf, an expert on Hawaiian seabirds. “We need to consider these data in order to make informed decisions about the best conservation measures.”

Declining population trends of Hawaiian Petrel and Newell’s Shearwater on the island of Kaua’i, Hawaii, USA is available at

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society, which merged with the American Ornithologists’ Union in 2016 to become the American Ornithological Society.

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AUTHOR BLOG: Tracking Yosemite’s Spotted Owls

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Tracking Spotted Owls in Yosemite National Park. Photo credit: S. Scherbinski

Stephanie Eyes

Linked paper: California Spotted Owl (Strix occidentalis occidentalis) habitat use patterns in a burned landscape by S.A. Eyes, S.L. Roberts, and M.D. Johnson, The Condor: Ornithological Applications 119:3, August 2017.

In 2005, I happily discovered the Student Conservation Association and that I could be an intern studying California Spotted Owls in Yosemite National Park. I accepted the internship and worked on a PhD student’s project investigating the effects of fire on California Spotted Owl occupancy. The final results from this study revealed that owl occupancy rates were similar between burned and unburned forest, but led to questions about how owls use the mosaic of post-fire patches. In 2010, the former PhD student, my graduate advisor, and I began our efforts to understand this question by capturing owls and affixing radio transmitters to them with the help of several technicians over the course of the three field seasons. By attaching a radio transmitter, we were able to use radio telemetry to triangulate the position of owls during nocturnal foraging bouts. Specifically, we wanted to know how owl foraging patterns are influenced by fire severity, fire-created edges, and other factors such as topography or distance to stream or nest/roost site.

After owls were captured, we set up our telemetry stations along the trails and roads surrounding our known owl roost sites. We went out in teams of two, each armed with a headlamp and an antenna, and worked to locate the owls within our burned sites. Once we initially identified that an owl was present with our antenna, we would split up, one person racing ahead so that we could get three different readings within ten minutes, each separated by about 200 meters, before the owl moved to a new foraging site. While I was relatively experienced with daytime radio telemetry, these nocturnal trail surveys posed a new challenge I enjoyed overcoming, and one time we encountered a curious mountain lion also using the trail searching for (I hoped!) something else.

Whenever we surveyed these trail sites, I remember wondering what the owl was hunting in the burned mosaic of forest patches at the moment that we were trying to pinpoint its location. I’m hoping all my wondering what they were eating will encourage me to go through all the pellets we found in burned forests!

After all the data was collected and analyzed, we learned that owls exhibited habitat selection for locations near roosts and edge habitats, as well as weak selection for lower fire severities. Our results highlight the importance of sustaining forests burned with a mosaic of fire severities with smaller patch sizes of high severity fire. Maintaining this complex mosaic of forest patches and focusing on protecting roost site locations may help sustain California Spotted Owls in the greater landscape.

Spotted Owls Benefit from Forest Fire Mosaic

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California Spotted Owls use a mosaic of fire-created habitat. Photo credit: S. Eyes

Fire is a crucial part of the forest ecosystem on which threatened Spotted Owls rely, but climate change and decades of fire suppression are changing the dynamics of these forests. A new study from The Condor: Ornithological Applications examines California Spotted Owl habitat use in Yosemite National Park and shows that while owls avoid the badly burned areas left behind by massive stand-replacing fires, they benefit from habitat that includes a mosaic of burned patches of different sizes and degrees of severity.

The National Park Service’s Stephanie Eyes (formerly of Humboldt State University) and her colleagues wanted to know how Spotted Owl foraging patterns are influenced by fire severity and fire-created edges, with the goal of informing future fuels reduction efforts and prescribed burning programs. They used radio-transmitters to track movements of 13 owls on eight territories in Yosemite National Park between 2010 and 2012 and found that overall, owls foraged near their roosts and along the edges of patches of burned forest, preferring these edge habitats. Owls selected larger burned patches than the average available size but avoided the interiors of severely burned patches.

“Maintaining a complex mosaic of forest patches with smaller patches of high severity fire can help sustain California Spotted Owls in the greater landscape,” says Eyes. “What’s unique about our study is that we investigated fires that burned within the natural range of variation, so it paints a picture of how owls used a burned landscape before the onset of today’s large stand-replacing fires.” Despite the owls’ preference for edges, there may be a threshold over which edges have a negative effect on habitat quality, and more research is needed to find the right balance between beneficial edge habitat and potentially harmful habitat fragmentation.

“This paper provides new radio telemetry data on how owls use home ranges that have had recent wildfires,” according to the University of Minnesota’s R.J. Gutiérrez, an expert on Spotted Owl habitat use. “Eyes and her colleagues provide a new piece of the puzzle about how owls respond, and they show that this response can be complex. More importantly, because their work occurred within a national park, it will serve as a ‘natural control’ that can be compared with other owl–fire studies occurring on managed forests.”

California Spotted Owl (Strix occidentalis occidentalis) habitat use patterns in a burned landscape is available at

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society, which merged with the American Ornithologists’ Union in 2016 to become the American Ornithological Society.

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New Details on Nest Preferences of a Declining Sparrow

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A Bachman’s Sparrow. Photo credit: J. Winiarski

Theory says that birds should choose nest sites that minimize their risk of predation, but studies often fail to show a connection between nest site selection and nest survival. Understanding these relationships can be key for managing declining species, and a new study from The Condor: Ornithological Applications explores the nest site preferences of Bachman’s Sparrow, a vulnerable songbird dependent on regularly burned longleaf pine forests in the southeastern U.S.

Jason Winiarski of North Carolina State University and his colleagues monitored a total of 132 Bachman’s Sparrow nests in two regions of North Carolina, the Coastal Plain and the Sandhills, measuring a variety of vegetation characteristics. They found several differences between the two regions in what sparrows looked for in a nest site—in the Coastal Plain, they favored low grass density and greater woody vegetation density, while birds in the Sandhills selected intermediate grass density and greater tree basal area. However, none of these features turned out to be related to nest survival.

According to the researchers, the differences between the two regions are likely due to differences in the available plant communities. Bachman’s Sparrows also could be selecting nest sites that allow easy access to nests or maximize the survival of fledglings once they leave, and these aspects may warrant further investigation. Regardless, Winiarski and his colleagues believe their results show the importance of management that mimics historical fire regimes in longleaf pine ecosystems, in order to maintain the diverse groundcover types used by the birds.

The most challenging part of the study was locating sparrow nests to monitor. “Bachman’s Sparrows are notoriously secretive and don’t easily give up the location of their well-hidden nests,” says Winiarski. “Eventually, we stumbled upon a technique of patiently watching adult sparrows at a distance that allowed the birds to behave normally, while being close enough for us to just barely see where they landed with food or nest material. That let us narrow down where the nest site was to within a few meters, and luck and thorough searching led us the rest of the way.”

“It is really remarkable that the authors were able to track the large number of Bachman’s Sparrow nests that they were able to find. As someone who has searched and searched for nests of this species, it is really hard,” according to Purdue University’s John Dunning, an expert on Bachman’s Sparrow ecology who was not involved with the research. “The study shows how consistent management of vegetation structure through the use of prescribed fire remains the most important management and conservation strategy to support breeding populations of Bachman’s Sparrow.”

Nest-site selection and nest survival of Bachman’s Sparrows in two longleaf pine communities is available at

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society, which merged with the American Ornithologists’ Union in 2016 to become the American Ornithological Society.

AUTHOR BLOG: Tell me a story! A plea for more compelling conference presentations

Kathryn Langin

Linked paper: Tell me a story! A plea for more compelling conference presentations by K.M. Langin, The Condor: Ornithological Applications 119:2, May 2017.

At one point during last year’s North American Ornithological Conference, I found myself rushing down the hallways to catch a talk by a senior scientist whose research I have long admired. As I took my seat and he began speaking, I was immediately struck with the thought: “Darn, why did I make this mistake again?”

My mistake? Deciding to attend his talk and, in the process, failing to remember that I loathe his presentation style. The slides are always filled to the brim with volumes of text and a seemingly endless number of teeny-tiny figures. And despite going through them at a sprinter’s pace, he somehow fails to finish in the allotted fifteen minutes. It happens every time. The audience experience is akin to watching an action-packed commercial but, in the end, having only a vague sense of what was being advertised.

That incident and many others propelled me to write the Commentary “Tell me a story! A plea for more compelling conference presentations,” published this week in The Condor: Ornithological Applications. In it, I argue that scientists should spend less time trying to impress their audience with mountains of data and more time implementing principles of good storytelling. I know this probably elicits a negative reaction in some readers, but hear me out.

Stories aren’t a mode of communication restricted to fictional tales. They are the most effective way to package information so that others can process and remember it (which is really the whole point of communication, right?). It’s difficult to recall a series of random facts; it’s much easier to recall the details of an engaging story.

The nice thing about storytelling is that it is a natural fit for the scientific process. Dr. Randy Olson, author of the book Houston, We Have a Narrative: Why Science Needs Story, defines a story as “a series of events that happen along the way in the search for a solution to a problem.” Sound familiar? As scientists, we are always in hot pursuit of a solution to a problem, but unfortunately we don’t always present our research that way.

So how can we change that? For starters, it’s not sufficient to package information in a logical order with a beginning (introduction), middle (methods and results), and end (conclusions). That’s obviously helpful, but I argue in the paper that you need to go a step further and develop a compelling plot—something that compels your audience to follow along with your journey of discovery. That can be accomplished by clearly articulating a problem to be solved and spending time convincing the audience why they should care about the problem in the first place.

In his book, Dr. Olson outlines a strategy that I find particularly helpful. He suggests framing your story’s plot by proclaiming something that scientists know and something else that scientists know, but then pointing out a critical unsolved problem or point of debate that, therefore, highlights a need for your particular study. He calls this his “and, but, therefore” template, which contrasts with the template used by many scientists: one that strings along a series of facts with “and, and, and” statements. There’s no drama in “and, and, and” statements, but there is with the “and, but, therefore” framework.

A key advantage of Dr. Olson’s approach is that—by setting the stage in an informative and captivating manner—you can bring your entire audience with you on your journey, not just the people who already understand and appreciate your field and study system. And that should be the ultimate goal: to engage the widest fraction of your audience as possible.

The ornithological community is doing important and interesting science, but we don’t always do a great job communicating it, even amongst ourselves. In my paper, I argue for more storytelling, but I also discuss a greater range of strategies for giving effective presentations, including the benefits of visually-engaging slides. I don’t expect everyone to agree with me, but it is my hope that this opinion piece will generate thought and discussion about how to best communicate our science. We can’t afford to let important research be lost in a sea of ineffective communication.