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

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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

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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.

Sandpiper Detectives Pinpoint Trouble Spots in Continent-Wide Migration

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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.

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Eagles Migrate Through Bad Weather to Arrive in Time to Nest

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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.

Endangered Ibises Benefit from Joining Egret Flocks

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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.

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How Reliable Are Traditional Wildlife Surveys?

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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.

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

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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.

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