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The official blog of ornithology journals The Auk and The Condor
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AUTHOR BLOG: ‘Bare Parts’ are an Important but Underappreciated Avian Signal

Wed, 05/24/2017 - 10:26

Two female American Goldfinches in an antagonistic interaction. Bill-color, derived from carotenoids, is a signal of dominance among female goldfinches but not among males. Image credit: K. Tarvin

Erik Iverson

Linked paper: The role of bare parts in avian signaling by E.K. Iverson and J. Karubian, The Auk: Ornithological Advances 134:3, July 2017.

Birds are well-known for being among the most colorful of all animals, with many species displaying striking, brightly-colored feathers. Scientists have long wondered why color is so important to fitness, and hundreds of studies have been published on the relationships between plumage and traits such as age, physiological condition, reproductive success, and attractiveness to mates. However, there is a growing awareness that plumage is not the only important site of coloration among birds; there is also considerable variation within and between species in the color of bills and in bare skin such as legs, feet, ceres, or wattles. Yet compared to plumage, these ‘bare part’ ornaments have received relatively little attention; a 2006 review of carotenoid coloration in birds, for instance, identified only 14 studies of bare parts versus 130 studies of plumage.

Unlike plumage, bare part color has the potential to be highly flexible. For example, carotenoid-based bare parts can lose their color within days of food deprivation or within hours of stress. Amidst growing suggestions that changes in bare part color could have important implications for signaling, one of the authors, Jordan Karubian, was studying Red-Backed Fairywrens (Malurus melanocephalus) in Australia. In this species, males either acquire a territory and display black breeding plumage and bills, or stay dull and serve as helpers at the nest. Jordan noticed that when a breeding male died and a dull male took over its vacancy, the dull male’s bill would darken within several weeks. Experiments confirmed this effect and showed that dull males with newly black bills also had testosterone levels comparable to birds with black plumage. I joined Jordan’s lab as an undergraduate and studied fairywrens as well, and when I was looking for a topic for an honors thesis Jordan suggested that bare parts were an expanding area in need of a review. That thesis grew and grew, eventually becoming my master’s work and encompassing 321 published studies of bare-part coloration and signaling.

Our review shows that despite the research focus on plumage, bare part signals might be more common than plumage-based ones and are an important visual signal in many species that lack bright plumage altogether. Carotenoids, melanin, and structural colors are all flexible in bare parts, and rapid blood flushing through skin can change color even more rapidly. Bare part color provides up-to-date information about a signaler, allowing competitors, mates, and offspring to adjust their strategies and maximize their fitness. Carotenoid-signaling with bare parts may also be less costly than with plumage, allowing signaling by females and non-breeding males. In species where both plumage and bare parts of the same color exist, the two are likely to be ‘multiple messages,’ conveying different aspects of condition or targeting different audiences. We believe that more careful and extensive characterization of bare part coloration will contribute greatly to our understanding of this underappreciated dynamic signal, and help inform a more inclusive theory of animal communication.


Song Diversity Hints at Thrushes’ Evolutionary Past

Wed, 05/24/2017 - 09:50

A spectrogram of a Hermit Thrush song shows the introductory note (at left) and the more complex song that follows.

The Hermit Thrush is famous for its melodiously undulating song, but we know very little about whether—and if so, how—its songs vary across the large swath of North America that it calls home in the summer. A new study from The Auk: Ornithological Advances provides the first thorough overview of geographic variation in Hermit Thrush song structure and hints at how isolation and adaptation shape differences in the tunes of a learned song within a species.

Sean Roach and Leslie Phillmore of Nova Scotia’s Dalhousie University gathered recordings of Hermit Thrush songs from a number of databases, accumulating a sample of 100 individuals recorded across North America between 1951 and 2015. Spectrographic analysis revealed significant differences in song structure across the three major populations—Northern, Western Mountain, and Western Lowland—as well as within them. The most striking differences were in the pitch of the introductory notes that preface the birds’ songs, with Western Lowland thrushes producing higher, more variable introductory notes than their relatives elsewhere.

“Though Hermit Thrushes have a beautiful, well-known song, relatively little is known about their singing behavior,” says Roach. “Knowing how the species varies with respect to genetics and morphology, I became interested in how their song varies, as song can play an important role in processes like speciation.” Some of the variation the researchers found likely dates back to isolation of different Hermit Thrushes populations by ice sheets during the Pleistocene era, while differences between the two western groups may relate to body size, with larger birds producing lower-frequency songs. One group of high-altitude birds in the Canadian Rockies sang songs that stood out other members of their subspecies, which Roach and Phillmore believe is an adaptation to how sound carries in their open, shrubby habitat.

“Genetic studies of Hermit Thrushes in North America have defined three different groups of subspecies, with major splits most likely occurring as a consequence of two glaciation events. Roach and Phillmore show convincingly that these three major groups of Hermit Thrushes can also be defined by the introductory whistle note of their songs,” according to Williams College’s Heather Williams, an expert on song diversity who was not involved in the study. “The whistle note’s relative consistency across large geographical distances may be due to its role in long-distance communication of species or subspecies identity, while the remainder of the song could be under fewer constraints and its variability may carry more information about individual singers.”

Geographic variation in song structure in the Hermit Thrush (Catharus guttatus) is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-16-222.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.


Male Birds Adjust Courtship Behavior Based on Social Context

Wed, 05/17/2017 - 09:59

A male junco reacts to a caged female. Photo credit: J. Welklin

Male birds that have already paired up with a female aren’t above looking for a little action on the side. A new study from The Auk: Ornithological Advances explores how male juncos adjust their courtship behavior to their social landscape, finding that while both paired and unpaired males will try to get the attention of a new female on their turf, they go about it in different ways.

A male bird’s courtship behavior can be affected by factors like his size and hormone levels, but ornithologists are increasingly realizing that social context—whether or not the male already has a mate, and what other birds are around to witness his exploits—also plays a role. Dustin Reichard of Ohio Wesleyan University (formerly Indiana University) and his colleagues set out to tease apart the roles these different issues play in the courtship of Dark-eyed Juncos, comparing how unpaired males, paired males whose mates were present, and paired males whose mates were elsewhere behaved when presented with a new female.

They found that paired males approached females more rapidly, spent more time close to the females, were more active, and spent more time with their body feathers erect than unpaired males. Paired males also sang fewer long-range songs than their single counterparts, perhaps not wanting other birds to overhear, although the actual presence or absence of their mates didn’t affect their behavior.

Reichard had noticed variation in male juncos’ behavior during previous work to record their courtship songs, which led him to start developing hypotheses about what might underlie those differences. “Our results highlight the importance of considering both intrinsic and extrinsic factors when investigating the causes of variation in male courtship behavior,” says Reichard. “The focus of the field has generally been intrinsic factors, such as male condition or circulating hormone levels, but our results suggest a potential role for eavesdroppers and social context in addition to condition-dependent factors.”

Reichard and his colleagues conducted their experiments at Mountain Lake Biological Station in Virginia, placing caged female juncos in front of free-living males and observing the males’ reactions. After each trial, the researchers captured the male to record his size and weight and take a blood sample. “Often the male’s mate would respond aggressively to the caged female, diving at the cage while pausing occasionally to chase her mate away from the area. The males were usually shameless during this process and continued to approach while singing and displaying, but to our knowledge none of the pairs in our study divorced as a result of this brief infidelity,” says Reichard. “People called me a ‘junco homewrecker’ during these experiments, but there’s little evidence to support that accusation.”

In the future, Reichard hopes to explore the possibility that males use different strategies to target potential social mates—females they’ll raise chicks with—versus “extrapair” mates. According to Auburn University’s Geoffrey Hill, an expert on mate choice in birds who was not involved in the research, “This study shows the potential for extremely complex behavioral interactions in birds that were long thought to be bland monogamists.”

Condition- and context-dependent factors are related to courtship behavior of paired and unpaired males in a socially monogamous songbird is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-16-214.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.


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

Fri, 05/05/2017 - 10:53

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.


Tracking Devices Reduce Warblers’ Chances of Returning from Migration

Wed, 05/03/2017 - 10:00

Geolocators like this one provide valuable data on bird migration but can also impact the birds that carry them. Photo credit: T. Boves

The tools ornithologists use to track the journeys of migrating birds provide invaluable insights that can help halt the declines of vulnerable species. However, a new study from The Condor: Ornithological Applications shows that these data come at a cost—in some cases, these tracking devices reduce the chances that the birds carrying them will ever make it back to their breeding grounds.

Geolocators are small devices attached to birds that record light levels over time, which can be used to determine location. They’re widely used to study migration patterns, but studies have suggested that some species may be negatively affected by carrying them. Douglas Raybuck of Arkansas State University and his colleagues monitored male Cerulean Warblers with and without geolocators to see how they fared, and they found that while geolocators had no effect on the birds’ nesting success in the same season following their capture, birds with geolocators were less likely to reappear on their territories after migration the next year—16% of geolocator-tagged birds returned from migration, versus 35% of the birds in the control group.

The data gained from geolocator studies are enormously useful for bird conservation, and on a global scale those benefits are likely to outweigh potential the costs. The results from this study suggest that the potential impacts of individual research projects need to be carefully evaluated, but we should remember that only a small number of birds are ever tagged relative to the total size of the population under study.

The researchers captured Cerulean Warblers in Pennsylvania, Missouri, and Arkansas by luring them into nets using call recordings and wooden decoys. Outfitting some with geolocators but others with only identifying color bands, they monitored the birds’ nests and then searched for them the following year to determine whether they’d returned. “Re-sighting males and identifying their unique color-band combinations as they moved about in the canopy was not always easy, but our dedicated and skilled field crew did a fantastic job of overcoming these obstacles, which were compounded by inclement weather and the rugged topography of the sites,” says Raybuck.

“New technologies such as geolocators and automated radiotracking arrays have led to a surge in new tagging studies of migratory songbirds,” according to York University’s Bridget Stutchbury, an expert on geolocators and the conservation biology of North America’s migratory songbirds. “Finding that tagged birds were far less likely to return the next year compared with un-tagged birds puts researchers in a serious dilemma, because despite the potential costs of tagging small birds, long-distance tracking is essential to find out which wintering and migratory stopover sites should be highest priority for conservation.”

Mixed effects of geolocators on reproduction and survival of Cerulean Warblers, a canopy-dwelling, long-distance migrant is available at http://americanornithologypubs.org/doi/full/10.1650/CONDOR-16-180.1.

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.


Review Highlights Challenges Faced by Birds in the Gulf of Mexico

Wed, 05/03/2017 - 09:57

More research is needed on the challenges faced by birds migrating through the Gulf of Mexico. Image credit: A. McBride

The Gulf of Mexico is hugely important to birds that migrate between North America and the Neotropics—almost all migrants have to go around it or across it. Coastal habitats around the Gulf of Mexico are critical for these migrating birds, but these habitats face more and more threats from human activity. A new Review in The Condor: Ornithological Applications brings together what we know—and don’t know—about the state of the region’s ecosystems and the birds that pass through them.

Understanding the population impacts of events during migration requires knowing which species are using what coastal habitats, how good those habitats are, where the birds are coming from, and where they’re going. Birds use a variety of coastal habitats, from vast tracts of hardwood forests to patches of vegetation embedded in agricultural or urban areas. The amount of food present in these areas, the intensity of competition for that food, and the danger from predators all shape how well a certain spot can meet a migrating bird’s needs. Threats to birds passing through the Gulf of Mexico include coastal habitat loss from forest clearing, wetland filling and dredging, and shoreline hardening; tall structures like cell phone towers and wind turbines; and, of course, climate change.

More data is needed in all of these subjects. Today the Gulf of Mexico Avian Monitoring Network is taking on the enormous task of coordinating monitoring across the region by integrating the efforts of multiple organizations and agencies. Doing this well will require close cooperation between the United States, Mexico, and Caribbean countries.

“Many migratory bird species are declining, including the species that breed in our backyards every summer, and we’re trying to understand if events that occur during migration might impact birds here on the breeding grounds. Our focus is the Gulf of Mexico region because it’s a bottleneck for migratory land birds—a place they have to move through every spring and fall,” says the Smithsonian Conservation Biology Institute’s Emily Cohen, the lead author of the Review. “Birds use these coastal habitats twice a year to eat and rest before and after their spectacular non-stop flight across the Gulf, which can take up to twenty hours! What’s going on during these migratory journeys is the final frontier for bird biology, and many new tools are making it possible to solve the mysteries of migration that previously limited our ability to develop conservation priorities.”

“This Review highlights the tremendous importance of the Gulf of Mexico to migratory birds, not only from an ecological and conservation perspective, but also as an opportunity to understand mechanisms that drive the evolution of migration across dozens of families,” according to Erik Johnson of Audubon Louisiana, an expert on bird conservation in the region. “As this paper makes clear, preserving this landscape is a tremendous responsibility shared across multiple countries, and our collective success has implications for how our descendants across North America will experience the amazing phenomenon of bird migration.”

How do en route events around the Gulf of Mexico influence migratory landbird populations? is available at http://americanornithologypubs.org/doi/full/10.1650/CONDOR-17-20.1.

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: Common Murre Parenting 101: How to Negotiate for an Easier Job

Wed, 04/26/2017 - 13:36

Researcher Linda Takahashi observes nesting murres. Photo credit: N. Oberlander

Linda Takahashi

Linked paper: Turn-taking ceremonies in a colonial seabird: Does behavioral variation signal individual condition? by L.S. Takahashi, A.E. Storey, S.I Wilhelm, and C.J. Walsh, The Auk: Ornithological Advances 134:3, July 2017.

When mates share parenting duties, conflict can arise over which one performs the hardest jobs. Common Murres are monogamous long-lived seabirds that raise only one chick each year. Extensive contributions from both parents are obligatory for successful chick fledging: Chicks are rarely abandoned, and murres are great parents. Throughout the three week chick-rearing period, one parent remains at the nest site, brooding and defending the chick, while the other is most often away from the colony foraging.  Murres have the highest wing loading of any flying bird, and so foraging far away from the colony, which is often necessary in years of reduced capelin availability, is energetically costly. Remaining in the colony with the chick is simply the easier job.

All things being equal between the murre parents, we’d expect that they would take turns and share the harder job of chick provisioning. For the most part, this is indeed what they do. One mate returns to the colony with a fish, feeds the chick, and the takes over brooding duties while the former brooder leaves. We called this a regular nest relief. However, some nest reliefs are irregular, such as when the returner comes back without a fish or the brooder doesn’t give up the chick, causing the returner to leave again to forage. We wondered if variation in nest reliefs was related to the relative physiological condition of the partners and whether changes in specific behaviours that occur during the nest relief ceremony were indicators of the partners “negotiating” with each other for the easier parental job.

Until our study, little focus had been given to the often-subtle behaviours shown by murres during nest relief (turn-taking) ceremonies. We looked at 16 pairs of Common Murres breeding in Witless Bay, Newfoundland, Canada, in 2009, a year with particularly low availability of capelin, the preferred forage fish. Pairs were identified by colour bands and nest location on the cliff. From dawn to dusk, we sat in a tiny observation blind and recorded murre behaviors with either a camcorder or an event logger. Specifically, an interaction began when a returning bird arrived at the nest, typically with a fish, and joined its chick-brooding partner, and it ended when one of the pair departed. We noted whether the parents traded roles and recorded their patterns of allopreening and bill-fencing. We also examined the relationships between murre condition—specifically, body mass and lipid metabolite levels (as measured by beta-hydroxybuterate)—and behavioural variation during turn-taking.

We found that irregular turn-taking ceremonies took longer than regular ones and had either delayed or non-synchronous allopreening. When a returning partner came to the nest without a fish, it began allopreening sooner than both the brooding partner and birds that returned with a fish. These “no fish” irregular nest reliefs took the longest of all, and brooders appeared to resist or delay leaving the colony. In cases where there was no exchange of duties, i.e., the brooder remained in the colony, rates of allopreening by the brooder were significantly lower than they were in all other types of turn-taking ceremony. Birds with higher overall chick-feeding rates brought fish on more visits than other birds, suggesting that that they were higher-quality individuals. Furthermore, brooding birds in relatively better condition departed the colony sooner after their mate fed the chick compared to those in relatively worse condition. We suggest that variation in allopreening allows mates to communicate with each other regarding their own condition, and, if that condition is poor, to negotiate for the easier parental duty, i.e., brooding.

Why would murres benefit from responding to signals about their mates’ condition? Since murres typically retain their mates for several years, parental investment theory predicts that it is in an individual’s best interest to preserve their mate’s current and future body condition as well as their own. Deterioration of a mate’s condition could lead to nest abandonment or even compromised survival. This paper shows that variation in ceremonies is one way to make information available to mates. Thus, behavioural variation during the ceremony can signal individual condition and be a means to negotiate parental roles.


Seabird Parents Compensate for Struggling Partners

Wed, 04/26/2017 - 13:36

A Common Murre at its nest. Photo credit: L. Takahashi

For species where both parents work together to raise their offspring, cooperation is key—it’s as true for birds as it is for us! A new study from The Auk: Ornithological Advances shows how pairs of Common Murres update each other on their condition so that when one partner needs a break, the other can pick up the slack.

Common Murre parents trade duties throughout the day—one stays at the nest while the other leaves to forage, hopefully coming back with a fish for the chick. Because brooding the chick requires much less energy than foraging, staying at the nest is preferable for a bird that’s in poor condition. Linda Takahashi, Anne Storey, and Carolyn Walsh of Newfoundland’s Memorial University, along with Sabina Wilhelm of the Canadian Wildlife Service, studied the “turn-taking ceremony” that parents perform when they switch places. They found that the time they spend preening each other provides a way for the two birds to exchange information about how they’re doing, so that if one is in poor shape the other can compensate.

The researchers observed 16 pairs of murres with chicks on an island off the coast of Newfoundland in summer 2009, recording their behavior when parents switched duties at the nest and capturing the birds to check their body condition. Their results show that these “nest relief” interactions take longer when one partner is especially low in body mass, suggesting that when brooders withhold preening and stall their departure, they’re letting their mates know that they need more time to rest; the returning mate can then compensate by going off to forage again rather than trading places immediately. Similarly, the brooding mate might let a struggling returner take over take over at the nest even if they haven’t brought back a fish.

“We had been doing murre field work for years in Witless Bay studying reproductive and parental behavior, and we became intrigued with the variation that we saw among pairs in their nest relief behaviors,” says Walsh. “Some nest reliefs were short and businesslike, while other nest reliefs seemed to involve a lot of interaction between the mates, and it took a long time for the mates to exchange brooding duty. When Linda Takahashi came to Memorial University as a master’s degree student, we decided that her project should focus on getting the details about this very interesting variation in murre nest relief behaviors.”

“The roles of avian pair members have been much studied in terms of energy investment and food delivery, but we are accustomed to thinking of these problems in terms of evolutionary tradeoffs. The ways in which contributions are actually negotiated within individual pairs has, until recently, been largely overlooked,” according to longtime seabird researcher Tony Gaston of Environment Canada. “Linda Takahashi’s paper addresses this deficiency, and this is a field which promises to open up additional avenues of research on within-pair communication.”

Turn-taking ceremonies in a colonial seabird: Does behavioral variation signal individual condition? is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-17-26.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.


Under-Studied Boreal Habitat Key for North America’s Ducks

Wed, 04/19/2017 - 10:10

Researchers used ducks harvested by hunters to learn new details about waterfowl migration. Photo credit: M. Carriere

Knowing where migrating birds came from and where they’re headed is essential for their conservation and management. For ducks, most of this information comes from long-term bird-banding programs, but this type of research has limits—despite all the birds harvested by hunters, only a small percentage of banded birds are ever recovered. A new study from The Condor: Ornithological Applications takes on the challenge of gaining information from unbanded birds by using stable isotope ratios, which reflect where birds were living while growing their feathers. These results reveal that the northern reaches of Canada may have underappreciated importance for North America’s waterfowl.

Canada’s Saskatchewan River Delta is North America’s largest inland delta and is a key stopover site for migrating ducks. To learn more about the origins of ducks using delta habitat, Christian Asante of the University of Saskatchewan, Keith Hobson of the University of Western Ontario, and their colleagues analyzed the isotopes in feather samples from 236 ducks from five species, all harvested by hunters in the region during migration in 2013 and 2014. Hydrogen and sulfur isotope ratios give scientists different information—hydrogen isotope ratios vary predictably with latitude, while sulfur isotope ratios reflect the type of food a bird eats and underlying geology—but together they indicated that as many as half the ducks using the delta during migration originated in the vast and nearly inaccessible areas of boreal forest and wetlands to the north.

The research required close collaboration with the area’s hunters. “Working on this project was a great experience,” says local community member Michela Carriere, who was hired to do the field work for the study. “I spent a few weeks collecting samples from the ducks and getting to know the hunters and the guides. Twice a day a load of ducks would come in and I would collect samples and label and package them, plucking feathers and extracting tissues. The hardest part was the labeling, which has to be done meticulously. I would spend hours each day collecting and organizing the samples.”

The results show that the boreal habitat’s contribution to North America’s waterfowl populations, though poorly documented, may be crucial. This region faces increasing threats from climate change and other factors, and isotopic monitoring offers a new means of tracking the effects on birds. “Our study is important for two reasons,” says Hobson. “First, it demonstrates clearly that the delta is a major fall refueling station for birds breeding in the north. Second, it shows once again how origins and regions of productivity can be determined using the simple isotope approach with feathers from hunter-killed birds. This major potential tool in waterfowl management has been largely overlooked in North America for too long.”

Tracing origins of waterfowl using the Saskatchewan River Delta: Incorporating stable isotope approaches in continent-wide waterfowl management and conservation is available at http://americanornithologypubs.org/doi/abs/10.1650/CONDOR-16-179.1.

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.


Time-Lapse Cameras Provide a Unique Peek at Penguins’ Winter Behavior

Wed, 04/19/2017 - 09:38

Gentoo Penguins at a breeding site in winter, as captured by a time-lapse camera. Image credit: T. Hart

Not even the most intrepid researcher wants to spend winter in Antarctica, so how can you learn what penguins are doing during those cold, dark months? Simple: Leave behind some cameras. Year-round studies across the full extent of a species’ range are especially important in polar areas, where individuals within a single species may adopt a variety of different migration strategies to get by, and a new study from The Auk: Ornithological Advances uses this unique approach to get new insights into Gentoo Penguin behavior.

Gentoo Penguins are of interest to scientists because they’re increasing at the southern end of their range in the Western Antarctic Peninsula, a region where other penguin species are declining. Little is known about their behavior during the nonbreeding season, so Caitlin Black and Tom Hart of the University of Oxford and Andrea Raya Rey of Argentina’s Consejo Nacional de Investigaciones Cientificas y Técnicas used time-lapse cameras to examine patterns in Gentoo Penguins’ presence at breeding sites across their range during the off season. They found both temporal and spatial factors driving winter attendance—for example, more Gentoo Penguins were present at breeding sites when there was open water or free-floating pack ice than when the shoreline was iced in, and more Gentoo Penguins were at breeding sites earlier in nonbreeding season than later.

The researchers deployed the cameras at seven sites including Argentina, Antarctica, and several islands. Each camera took eight to fourteen photos per day, and volunteer “citizen scientists” were recruited to count the penguins in each image via a website (penguinwatch.org). Overall, the seven sites fell into three distinct groups in terms of winter attendance, each with its own patterns of site occupation. These findings could have important implications for understanding how localized disturbances due to climate change and fisheries activity affect penguin populations during the nonbreeding season.

“Working with cameras allows us to understand half of this species’ life without having to spend the harsh winter in Antarctica. It has been exciting to discover more about why Gentoos are present year-round at breeding sites without having to handle a single bird,” says Black. “I believe the applications for this technology are far-reaching for colonial seabirds and mammals, and we are only just beginning to discover the uses of time-lapse cameras as deployed virtual ecologists in field studies.”

“What most seabirds do away from their nest is often anybody’s guess. For Antarctic birds, this is compounded by the long periods of darkness that penguins and others must face in the winter,” adds Mark Hauber, Editor-in-Chief of The Auk: Ornithological Advances and Professor of Animal Behavior at Hunter College and the Graduate Center of the City University of New York. “This new research in The Auk: Ornithological Advances on Gentoo Penguins colonies reveals critical year-to-year differences in where the birds are when they are not nesting: In some years, only the most temperate sites are visited, and in other years both southerly and northerly locations are busy with penguins.”

Peeking into the bleak midwinter: Investigating nonbreeding strategies of Gentoo Penguins using a camera network is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-16-69.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.


AUTHOR BLOG: How the ‘Mitey’ Have Fallen: Impacts of Burrowing Skin Mites on Reproduction of an Urban Raptor

Wed, 04/12/2017 - 10:42

Black Sparrowhawks displaying symptoms of mite infection.

Julia L. van Velden

Linked paper: Negative effect of mite (Knemidokoptes) infection on reproductive output in an African raptor by J.L. van Velden, A. Koeslag, O. Curtis, T. Gous, and A. Amar, The Auk: Ornithological Advances 134:3, July 2017.

Parasites were once considered to be one of the less important factors that limit or regulate animal populations, with the impacts of predators and resource limitation previously receiving far more attention. This lack of attention probably stemmed from the mistaken belief that most parasites have evolved not to harm their hosts too much, because if their host dies, they lose the resource they depend on. We now know, however, that parasites can often strongly affect both a host’s reproduction and survival rates. Our new study published in The Auk: Ornithological Advances adds to this knowledge for a relatively understudied parasite in a wild raptor population.

Knemidokoptes mites are a genus of microscopic skin mites which burrow into the skin of birds and cause the “scaly leg” and “scaly face” conditions that are frequently seen in caged and domestic birds. They also occur in some wild species, particularly passerines. However, these parasites have rarely been recorded on raptors, except on captive birds. Additionally, almost no research has been carried out to investigate the impacts of these parasites on species’ fitness. Our study explored the symptoms of infection and the impact these mites have on the breeding performance of a wild population of Black Sparrowhawks in Cape Town, at the southernmost tip of South Africa.

Knemidokoptes skin mites.

Black Sparrowhawks are a recent colonist to this mostly urban area, and urban living may come with associated changes in exposure to parasites and pathogens. Our study population has been closely monitored since 2001 and has grown steadily over the years, with the population now containing around 50 breeding pairs each year. In 2007, we started to notice birds in the population with strange symptoms, namely balding heads and scaly lesions on their legs. These birds appeared to be agitated and in poor condition. Post-mortem investigations revealed that, in all cases, birds with these symptoms were infected with the burrowing skin mite (Knemidokoptes spp.). We found that in some years, up to 5% of the Cape Peninsula population was infected, which represents a highly novel finding for a wild population of raptors.

Comparing between the sexes, we also found that mite infection was more frequent for males than females. Higher parasitic infection of males has been found for several other studies in different parasites and may be the result of fundamental biological and behavioural differences. In our population, we suspect that Black Sparrowhawks may become infected by these mites from their prey, possibly domestic chickens, which are known to frequently be infected by Knemidokoptes mites. Like most Accipiters, Black Sparrowhawks pluck their prey before consumption, which may mean they have greater exposure to this parasite than other raptor species, and the fact that males are responsible for hunting throughout the breeding season may explain the male bias in infection.

Most importantly, we found that Black Sparrowhawks that were infected with these mites had considerably reduced breeding success. We compared breeding performance between infected and non-infected birds and also between birds pre- and post-infection. These analyses showed that infection reduced breeding performance by over 50%. This could be because adults become too agitated to incubate or hunt effectively following infection.

We also investigated if this infection was present anywhere else in South Africa and found four hotspots of infection. Three of the infection sites were cities, and thus infection by this mite may be associated with urbanization levels and the additional stresses this may incur. Other research has, however, not yet detected any negative effect of urbanisation on this species’ health.

Our study, the first on Knemidokoptes mites within a wild population of raptors, therefore suggests that this parasite could play a role in limiting the breeding performance of infected populations. Although Black Sparrowhawks are not a species of conservation concern, this study provides important information on the negative role such parasites can play in their host’s reproductive success, which will be important if this infection is found to occur in an endangered raptor species.


AUTHOR BLOG: Tracking Semipalmated Sandpiper Migration

Wed, 04/05/2017 - 10:07

Photo credit: B. Winn

Stephen Brown

Linked paper: Migratory connectivity of Semipalmated Sandpipers and implications for conservation by S. Brown, C. Gratto-Trevor, R. Porter, E.L. Weiser, D. Mizrahi, R. Bentzen, M. Boldenow, R. Clay, S. Freeman, M.-A. Giroux, E. Kwon, D.B. Lank, N. Lecomte, J. Liebezeit, V. Loverti, J. Rausch, B.K. Sandercock, S. Schulte, P. Smith, A. Taylor, B. Winn, S. Yezerinac, and R.B. Lanctot, The Condor: Ornithological Applications 119:2, May 2017.

The Semipalmated Sandpiper (Calidris pusilla) is a small shorebird, most commonly seen on migration along the coastlines of the eastern United States. It is historically one of the most widespread and numerous shorebird species in the Western Hemisphere, breeding across the North American Arctic tundra, but major population declines have been documented in the core of the nonbreeding range in northern South America. Breeding populations have also declined in the eastern North American Arctic, but appear to be stable or increasing in the central and western Arctic. To help understand what is causing the declines and work toward conservation of this species, we set out to track migration routes and stopover sites using light-level geolocators, a relatively new technology which determines the bird’s position on earth by measuring the length and timing of daylight throughout the year. The major challenge to using these tags is that you have to catch the bird once to put on the geolocator and then again the next year to retrieve it, which requires finding the same bird again in the vast arctic tundra. Luckily, they tend to return to the same breeding areas the next year.

Our large group of 18 partner organizations worked collaboratively to carry out the study across the entire North American Arctic from Nome, Alaska, to Hudson Bay, and we attached 250 geolocators to birds by mounting expeditions to 8 different field sites. Our field crews faced challenging conditions, working in the Arctic where the weather is always unpredictable and where both grizzly bears and polar bears regularly visit field sites. We repeated expeditions the next year to each site, and recovered 59 of the units by recapturing birds. The treasure trove of data showed migration routes and stopover sites from the entire year in the life of each bird, and showed that birds breeding in the eastern Arctic wintered in northeastern South America. Birds from eastern Alaska and far western Canada wintered from Venezuela to French Guiana. Central Alaskan breeders wintered across a very wide range from Ecuador to French Guiana. Birds that bred in western Alaska wintered mainly on the west coasts of Central America and northwestern South America, outside the nonbreeding region in which population declines have been observed.

Our results confirm that Semipalmated Sandpipers that breed in the eastern Arctic and use the Atlantic Flyway also use the areas in South America where population declines have been detected, suggesting that declines may be concentrated in populations along the Atlantic Flyway and in the eastern Arctic. However, because some birds from sites as far west as Barrow, Alaska, also used the areas in northeastern South America where declines have occurred, further work is needed to localize the geographic areas used by declining populations, and therefore the potential causes for the declines. We identified several new stopover and wintering areas, where implementing conservation actions to preserve the habitats used by Semipalmated Sandpipers could contribute to protecting the species. We measured a larger impact of geolocators on return rates than has been observed for larger shorebirds, indicating that caution should be used when working with small shorebirds, and that potential new information gains from additional geolocator studies should be weighed against expected impacts on individual survival. Our data also provided new insights about how long birds stay at migration stopover sites, which will be useful to studies that measure and monitor the total size of populations using these sites. Understanding the connections between breeding, migration, and wintering areas for these populations of a widespread yet declining shorebird can help future studies identify the causes of declines and ensure the effectiveness of targeted conservation efforts.


Sandpiper Detectives Pinpoint Trouble Spots in Continent-Wide Migration

Wed, 04/05/2017 - 09:56

A Semipalmated Sandpiper wearing a geolocator. Photo credit: B. Winn

Understanding and managing migratory animal populations requires knowing what’s going on with them during all stages of their annual cycle—and how those stages affect each other. The annual cycle can be especially difficult to study for species that breed in the Arctic and winter in South America. A new study from The Condor: Ornithological Applications tackles this problem for Semipalmated Sandpipers, historically one of the most widespread and numerous shorebird species of the Western Hemisphere, whose populations in some areas have undergone mysterious declines in recent years.

Stephen Brown, Vice President of Shorebird Conservation for Manomet, assembled a large group of partner organizations to deploy 250 geolocators, tiny devices that use light levels to determine birds’ locations, on adult sandpipers at sites across their breeding range in the North American Arctic. Recapturing 59 of the birds after a year to download their data, they found that the eastern and western breeding populations use separate wintering areas and migration routes. Birds that breed in the eastern Arctic overwinter in areas of South America where large declines have been observed. The researchers believe these declines are tied to hunting on the wintering grounds and habitat alteration at migration stopover sites, although their precise impacts remain unclear.

“This study was a response to the discovery of a large decline in the population of Semipalmated Sandpipers in the core of their wintering area in South America, and the need to determine which birds were involved. We didn’t know if the decline affected the entire population or just part of it,” says Brown. “Bringing together the 18 partner organizations that worked collaboratively on this project allowed us to track the migration pathways used by Semipalmated Sandpipers at the enormous geographical scale of their entire North American Arctic breeding range and provided critical new information about what sites are important to protect to support their recovery.”

“The authors here present one of the few studies that examine year-round connectivity, including stopover sites, of Arctic-breeding shorebirds,” according to the University of Guelph’s Ryan Norris, an expert on migration tracking who was not involved with the study. “Multi-site, range-wide studies on connectivity, such as this, are critical if we are to understand the population consequences of environmental change in migratory birds.”

Migratory connectivity of Semipalmated Sandpipers and implications for conservation is available at http://americanornithologypubs.org/doi/full/10.1650/CONDOR-16-55.1.

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.

About Manomet: Manomet is a nonprofit organization that believes people can live and work today in ways that will enable our world to thrive and prosper tomorrow. Manomet’s mission: applying science and engaging people to sustain our world. Visit www.manomet.org for more information.


Eagles Migrate Through Bad Weather to Arrive in Time to Nest

Wed, 04/05/2017 - 09:52

A Golden Eagle wearing a GPS transmitter. Photo credit: P. Fusco

Migration is tough, and birds do everything they can to optimize it. How do factors like weather and experience affect the strategies they choose? A new study from The Auk: Ornithological Advances shows that older, more experienced Golden Eagles actually migrate in poorer weather conditions and cover less ground than their younger counterparts, but for a good reason—they’re timing their efforts around raising the next generation of eagles.

Adrian Rus of Boise State University (now at Australia’s University of Sydney), Todd Katzner of the USGS, and their colleagues studied GPS telemetry tracks to evaluate the migratory performance of almost 90 Golden Eagles in eastern North America and determine how performance related to season, age, and weather. Unsurprisingly, eagles flew faster and farther when they had strong tailwinds and thermals to help them along. What was counterintuitive, however, was that older eagles did not cover more ground than younger eagles despite their greater experience. Instead, older eagles migrated in poorer weather conditions and travelled more slowly.

The researchers believe this is because older birds face different pressures than younger birds. Even if the weather is bad and will slow them down, they need to start heading north earlier than young birds that aren’t breeding, because they have to get back to their breeding grounds in time to reclaim their territories and start nesting. “Younger eagles just need to survive the summer, so they can be choosy about when they travel north and only migrate when conditions are really ideal for fast soaring flight,” explains Katzner.

Lead author Adrian Rus, who worked on the study as an undergraduate, enjoyed the challenges involved in analyzing the migration data. “The best part about working on this project was using specialized software to visualize the golden eagle migrations and being able to pair it with meteorological data to answer my biological questions,” he says. “As a result, the project greatly improved my geospatial and statistical analysis skills and was instrumental my current graduate research in animal movement ecology.”

“Rus et al. provide an unusual demonstration of the interaction between migration experience and seasonal environments,” according to Oklahoma University’s Jeff Kelly, an expert on avian migration. “It is likely that the migration experience that older birds have enables them to extend their summer season through early spring and late autumn migration despite declining atmospheric conditions. Rus et al.’s demonstration of this insight into the interaction between age and the migratory environment expands our thinking about the life history tradeoffs that occur across the annual cycle of migrants.”

Counterintuitive roles of experience and weather on migratory performance is available at http://americanornithologypubs.org/doi/abs/10.1642/AUK-16-147.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.


AUTHOR BLOG: A New Look at Altitudinal Migration

Wed, 03/29/2017 - 10:57

Alice Boyle

Linked paper: Altitudinal bird migration in North America by W.A. Boyle, The Auk: Ornithological Advances 134:2, April 2017.

I became a birder in my early 20s when I moved to Costa Rica to play in the Orquesta Sinfónica Nacional. I didn’t know many people at first, and my Spanish was, shall we say, a work in progress. When I left Canada, I was given a pair of binoculars and the (then) newly published “A Guide to the Birds of Costa Rica” by Stiles and Skutch. Armed with these tools, I would get on a bus headed in a different direction every time I had a day off from my music job. At first I managed to identify only a few of the dozens of species that would pass in riotous mixed flocks. Pretty soon I realized that I had to focus on looking and taking notes, only later to pore over the book to figure out what I had seen. While those evening book sessions were occasionally frustrating (“Dang… I should have checked if that flycatcher had one or TWO wing bars!”), I also enjoyed reading the eloquent descriptions of bird behavior and soon found myself engrossed in tropical natural history. One of the things that puzzled me from the start were descriptions of the seasonal migrations of birds within that tiny, lovely, benign country. I grew up in a place where bird migration seemed not only logical, but frankly the ONLY sensible thing to do in winter. But why would some birds move up and down mountains each year in a place where the weather is always warm and food hangs from the trees wherever you go?

This question ultimately became the topic of my PhD many years later, and I did get some satisfying answers (full details here). But one unsatisfactory aspect of my chosen topic was that few other researchers were asking similar questions in other parts of the world. What common themes from my tropical work might hold true for other regions? What about North American birds? How common are these altitudinal migrations in our mountains? What else is known about them? Finally, in this article, I have attempted to summarize that knowledge. It turns out that we have LOTS of birds in North America that make similar types of movements. In fact, roughly the same proportion of the North American avifauna migrate up and down mountains as does the Costa Rican avifauna—20% to 30% depending on how you count it. With the exception of the Himalayas, reports from other avifaunas seem consistent with this figure. The higher latitude of North America makes things interesting, creating varied combinations of seasonal movements along both elevational and latitudinal gradients, and several of the North American species make movements that stretch our tidy migration terminology in complex ways. There is a reason I had trouble as a grad student finding this literature, however. Much of the information, now summarized in the Birds of North America life history series, was originally reported in bird atlases, Masters theses, or dated natural history accounts. Furthermore, despite early naturalists’ interest in the topic, few authors have cared to document patterns or tried to understand causes of these movements in recent years.

Why might this be so? Part of the reason might have to do with geography; there are more ornithologists in the flatter and more populated eastern portion of the continent compared to the topographically complex west, and this fact may have steered our collective research interest in some way. Part might have to do with the perception that these are not “real” migrations. Certainly the short distances many altitudinal migrants traverse are not the jaw-dropping feats of athleticism displayed by Red Knots, Arctic Terns, or Blackpoll Warblers. But I argue that they are real in many important respects: they involve seasonal return movements between breeding and non-breeding areas on predictable schedules. The fact that such movements are often partial (not all birds migrate), facultative (not genetically hard-wired), and short-distance actually makes them more attractive subjects for many types of migration research. We have far better chances of determining what ecological conditions tip the cost-benefit balance toward migrating in species that have built-in control groups in the form of resident individuals. Furthermore, the more “messy” movements are undeniably a part of the rich diversity of strategies that animals use to cope with a constantly shifting environment. If we are to protect our avifauna for future generations, understanding these movements will be as important as understanding the marathon flights of the migration poster children. Perhaps this review will inspire a blossoming of interest in the birds who make mountains their home.

Find out more:
www.aliceboyle.net
On Twitter: @birdfiddler
Learn about what we do in the Boyle Lab by following our YouTube channel and Flickr stream


Endangered Ibises Benefit from Joining Egret Flocks

Wed, 03/22/2017 - 10:58

A Little Egret (far left) forages with endangered Crested Ibises. Photo credit: N. Zhao

Birds benefit from flocking together—even when they’re not of a feather. According to a new study in The Auk: Ornithological Advances, China’s endangered Crested Ibises benefit from joining forces with other, more visually-oriented bird species while searching for food.

Joining mixed-species flocks can reduce birds’ risk of predation while boosting their foraging opportunities, but it can also expose them to competition and disease, and little research has been done on what this means for birds such as ibises that rely on their sense of touch to find food. Yuanxing Ye and Changqing Ding of the Beijing Forestry University and their colleagues studied the behavior of Crested Ibises foraging with and without Little Egrets in central China’s Shaanxi Province, recording the birds’ behavior with a digital video camera to determine whether they picked up on social cues from the other species. They found that ibises in mixed-species flocks became alert to threats sooner, suggesting they felt less at risk when mingling with the more visually-oriented egrets.

Crested Ibises were once believed to be extinct in the wild, until seven birds were discovered in a remote area of China in 1981. Ye and his colleagues believe this new information about their foraging behavior could benefit ibis conservation. “Developing habitat conditions that favor mixed-species flocks may reduce the perception of risk by ibises due to the early warning effects of egrets, particularly in habitats with high levels of predation or disturbance,” according to Ye.

“Mixed-species flocks are a common occurrence in birds, but little is known about the costs and benefits of joining such groups when species differ in their foraging tactics,” adds the University of Montreal’s Guy Beauchamp, an expert on group living in birds. “In this case, ibises benefitted from joining another more visually-oriented species in that they detected threats more quickly. This study shows how detailed behavioral observations can help us understand why species forage in groups and also join other species.”

What makes a tactile forager join mixed-species flocks? A case study with the endangered Crested Ibis (Nipponia nippon) is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-16-191.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.


How Reliable Are Traditional Wildlife Surveys?

Wed, 03/22/2017 - 10:58

A Sandhill Crane from the Rocky Mountain population. Photo credit: T. Cacek

To effectively manage a wildlife species, one of the most basic things you need to know is how many of them are out there. However, it’s almost never feasible to count every single individual—so how do the results of wildlife surveys compare to true population size? A new study in The Condor: Ornithological Applications tests this using the results of more than thirty years of surveys of the Rocky Mountain population of Sandhill Cranes.

A three-year “moving average” is often used to smooth out year-to-year irregularities in survey results, but this approach has never been evaluated. Brian Gerber of Colorado State University and William Kendall of the U. S. Geological Survey assessed whether the annual population changes reported by these moving averages were realistic, based on what is known about crane demographics, and how they compared to the results of a more sophisticated statistical approach called a hierarchical Bayesian time series model. They found that while the moving average population estimates were reasonable, the more complex method performed better over a large number of scenarios.

Bayesian approaches offer a structured way to incorporate new information as it becomes available. “The model-based approach we looked at is very flexible and has some major advantages over other methods,” says Gerber. “By taking a Bayesian approach, we can include additional information about both the observation process and the true population to obtain more realistic estimates and predictions. Also, the model-based approach includes measures of uncertainty about our population estimates, which are not usually provided by more common approaches and are crucial for understanding the level of confidence we have about our estimates.”

Evidence suggests that management practices over the last twenty years have largely met the annual population objectives for the Rocky Mountain Sandhill Crane population. “Looking forward,” adds Gerber, “managers may still be interested in adopting our more robust modeling approach due to its flexible framework, which makes implementing any changes relevant to the survey easier.” The investment in collecting these long-term data may pay off not just for crane management, but for an advance in methods that can be applied to other species as well.

Evaluating and improving count-based population inference: A case study from 31 years of monitoring Sandhill Cranes is available at http://americanornithologypubs.org/doi/full/10.1650/CONDOR-16-137.1.

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: Bringing Mitochondria into Species Concepts

Wed, 03/08/2017 - 16:37

Geoffrey Hill

Linked paper: The mitonuclear compatibility species concept by G.E. Hill, The Auk: Ornithological Advances 134:2, April 2017.

A couple of years ago I was at the Bentsen State Park hawk watch tower with a dozen other birders when the topic of species boundaries came up. No one knew me or that I was a professional ornithologist—I was deep undercover as a mediocre birder—so I just listened to the conversation. Someone suggested that the “experts” changed species boundaries periodically so that new field guides would have to be printed and bought. The not-so-subtle suggestion was that the checklist committee was in the pockets of powerful publishers. Then it was suggested that researcher elites manipulated the system to get government money. Everyone quickly reached consensus that both of these views were correct. From that conversation, it would seem that scientists have not been very effective at conveying to the public the rationale for changes to the checklist. But maybe a skeptical public is not surprising given that some professional ornithologists are also not enamored with how species boundaries of birds are demarcated. This uncertainty regarding what is or is not a species could simply reflect the reality that at the tips of the branches of the tree of life, species boundaries are nebulous. But I don’t think that is correct. I agree with Ernst Mayr’s conclusions that species are real and fundamental biological entities. I’m convinced that the problem with the current approach to assessing species boundaries lies in a poor understanding of the process of speciation leading to an incomplete and confused species concept.

I lived the first fifty years of my life without offering any opinion about the process of speciation or species boundaries, and I had no plans to ever wade into the morass. It was therefore quite unexpected when I fell head first into the deep end of the speciation controversy by proposing a new definition for how to define an avian species, published as an opinion piece in The Auk. This new speciation concept arose not from phylogeographic studies—the genesis of all previous species concepts—but from the study of mating patterns in relation to colorful feathers (see Hill and Johnson 2012). Sexual selection and speciation have always been closely associated topics in evolutionary biology, but what I realized about five years ago is that both of these fundamental evolutionary processes emerge as a necessary outcome of the critical need for coadaptation between mitochondrial and nuclear genes and that mitonuclear coadaptation is the foundation of any comprehensive species concept. Before I explain what I mean by “mitonuclear coadaptation,” however, I need explain current dogma for recognizing species.

Whether it is explicitly stated or not, decisions regarding species boundaries are based on a species concept, and the Biological Species Concept currently being followed by the American Ornithological Society checklist committee was proposed by Ernst Mayr about 75 years ago, long before the age of modern genomics. As a matter of fact, the current species concept was written before biologists even knew that mitochondria have DNA that is inherited independently from the nuclear DNA.

It turns out the knowing about mitochondrial DNA is very important because mitochondrial DNA codes for components of the electron transport system, which is the biochemical machine that generates most of the energy for birds, mammals, and other complex life. But mitochondria only carry a few genes—not nearly enough to code for the entire electron-transport system—so much of the system is encoded by nuclear DNA, with the products moving over to the mitochondria to co-function with the products of mitochondrial genes. Having two distinct genomes coding for components that have to work together in a fully coordinated manner means that these genomes have to be coadapted; put another way, the genes in the mitochondria and nucleus have to coevolve so that their products are matched in physical shape and complementary of function. When populations become isolated, their mitochondrial and nuclear genes can coevolve to be different than the coevolved mitochondrial and nuclear genes of any other population such that they cannot be mixed without incompatibilities and fitness loss. What I propose in my opinion paper is that it is uniquely coadapted sets of mitochondrial and nuclear genes that define a species and that make hybrid offspring resulting from pairings between species less viable, thereby maintaining species boundaries.

Currently, it is not possible to assess the mitonuclear compatibility of any two populations of birds, although by simple extrapolation of advancing technology we will soon have such capability. What we currently have is information on the mitochondrial genotype of many species of birds, including many populations that are potentially distinct species. I propose that uniquely co-adapted mitonuclear genotypes necessarily involve unique mitochondrial genotypes. Thus, mitochondrial genotype becomes an excellent and available proxy for species boundaries.

Many biologists already look to mitochondrial genotypes when assessing species status.  My theory simply provides stronger justification for placing more emphasis on mitochondrial genotypes and less emphasis on nuclear genotypes. Indeed, advocates of DNA barcoding assert that most species can be unambiguously diagnosed by mitochondrial gene sequence, and my theory potentially explains why.

As with any new idea, this hypothesis for the process of speciation and nature of species boundaries must be tested. Whether the mitochondrial compatibility species concept proves to be accurate or an overstatement, ornithology will benefit by considering mitonuclear interactions when they ponder species boundaries.


Redefining “Species”: New Species Concept Based on Mitochondrial & Nuclear DNA Coadaptation

Wed, 03/08/2017 - 15:13

A hybrid “Brewster’s” warbler. Photo credit: L. Spitalnik

What is a species? Biologists—and ornithologists in particular—have been debating the best definition for a very long time. A new commentary published in The Auk: Ornithological Advances proposes a novel concept: that species can be defined based on the unique coadaptations between their two genomes, one in the nuclei of their cells and the other in their mitochondria.

All animals have two sets of genes, one in the cell nucleus and one in organelles called mitochondria, and these two sets of DNA work together to enable cellular respiration and energy production. If they’re mismatched, the result is reduced energy output and increased production of damaging free radicals. While the most commonly used species definition is based on the idea that isolated populations slowly accumulate changes in their nuclear genes that make interbreeding impossible, Auburn University’s Geoffrey Hill proposes a new twist on the species concept—that speciation is really the divergence of sets of coadapted mitochondrial and nuclear genes. Interspecies hybrids, his theory suggests, have reduced fitness due their mismatched genomes’ reduced ability to work together in the cell.

Past studies have shown that mitochondrial genotype tends to be very good at showing species boundaries between birds. This “mitonuclear compatibility species concept” helps explain the fact that the abrupt transitions between mitochondrial genotypes at species boundaries correspond with abrupt transitions in songs, plumage patterns, and female mating preferences. Interestingly, two closely related species that have recently been documented to have extensively intermingled nuclear genes—Blue-winged and Golden-winged warblers—also show an abrupt transition in mitochondrial genes.

“Almost all ornithologists who write and think about avian speciation study phylogeography—the geographical distribution and genetic structure of bird populations,” says Hill. “In contrast, I study bird ornamentation and, particularly, bird coloration. It was the discovery that ornaments signal mitochondrial type that led to my sudden realization that mitochondrial type—or, more accurately, coadapted sets of mitochondrial and nuclear genes—define species boundaries. I don’t think I would have ever seen the pattern if I had come at the question from a phylogeographic perspective.”

“This is an intriguing and controversial idea—that mitonuclear incompatibilities could be so central to generating new avian species—and I see this as a call for more research into how these incompatibilities might manifest themselves in young species,” says avian evolutionary biologist David Toews of Cornell University. “The functional aspects of mitochondrial genes have, in particular, received little attention from the ornithological community, and it will be interesting to see how these ideas play with additional empirical studies going forward.”

The mitonuclear compatibility species concept is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-16-201.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.


Monitoring Birds by Drone

Wed, 02/15/2017 - 10:15

Researchers test the bird monitoring drone. Photo credit: A. Wilson

Forget delivering packages or taking aerial photographs—drones can even count small birds! A new study from The Auk: Ornithological Advances tests this new approach to wildlife monitoring and concludes that despite some drawbacks, the method has the potential to become an important tool for ecologists and land managers.

Bird surveys provide crucial data for environmental management, but they have limitations—some areas are difficult to access, and surveyors vary in their skills at identifying birds. Using audio recordings made by unmanned aerial vehicles (UAVs) can help to combat both of these pitfalls, as hard-to-reach sites can be flown over and multiple people can review the resulting recordings. Andrew Wilson of Gettysburg College and his colleagues tested the feasibility of this approach by using fishing line to suspend an audio recorder from a simple “drone,” first in trial runs on college athletic fields and then in real bird surveys on Pennsylvania State Game Lands.

The experiments on state game lands directly compared UAV data with traditional ground-based surveys of the same areas. A few bird species were undercounted by the UAV technique, such as Mourning Doves, whose extremely low-frequency calls weren’t picked up by the recorder, and Gray Catbirds, which occurred at such high densities that counting individual birds in the recordings was difficult. Overall, however, there were few significant differences between the results produced by the two methods.

“The inspiration for the study came while I was surveying forests in the Appalachian Mountain in Pennsylvania for Cerulean Warblers,” says Wilson. “All of our survey work was done from roadsides or hiking trails, for logistical reasons and to maximize survey efficiency, but I was always aware that our sample locations were very biased and that we were missing key areas such as steep forested slopes.” He notes that the drone and audio recorder used in this experiment were inexpensive, commercially available models, making this technique within reach even for those with limited funding.

“I recall my vocal reaction upon hearing their oral presentation during a session I chaired on emerging technologies to study birds at the 2016 North American Ornithology Conference last August, where I exclaimed, ‘What an amazingly simplistic but useful application of a drone for bird research—I wish I had thought of it!’” says McGill University’s David Bird, founding editor of the Journal of Unmanned Vehicle Systems. “This unique study provides a significant first step toward the inevitable common use of unmanned vehicle systems for monitoring songbird populations both during the breeding season and on migration.”

The feasibility of counting songbirds using unmanned aerial vehicles is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-16-216.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.


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Welcome to the American Ornithological Society (AOS)
Advancing Scientific Knowledge and Conservation of Birds

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