Male Birds Adjust Courtship Behavior Based on Social Context

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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.

Tracking Devices Reduce Warblers’ Chances of Returning from Migration

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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.

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Review Highlights Challenges Faced by Birds in the Gulf of Mexico

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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.

Seabird Parents Compensate for Struggling Partners

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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

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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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