Prairie-Chicken Nests Appear Unaffected by Wind Energy Facility

CONDOR-17-51 L Powell

Prairie chickens nests appear unaffected by the proximity of a small wind energy facility. Photo credit: L. Powell

Wind energy development in the Great Plains is increasing, spurring concern about its potential effects on grassland birds, the most rapidly declining avian group in North America. However, a new study from The Condor: Ornithological Applications suggests that for one grassland bird species of concern—the Greater Prairie-Chicken—wind energy infrastructure has little to no effect on nesting. Instead, roads and livestock grazing remain the most significant threats to its successful reproduction.

Prairie-chickens are thought to avoid tall structures such as wind turbines because they provide a perch from which raptors can hunt. To learn more, the University of Nebraska–Lincoln’s Jocelyn Olney Harrison and her colleagues gathered data on the effects of an existing small wind energy facility (36 turbines) in Nebraska. They captured 78 female prairie-chickens at breeding sites, or leks, ranging from less than a kilometer from the wind energy facility to more than twenty kilometers away, and fitted the birds with transmitters to track them to their nests. Monitoring their nesting success and collecting data on the habitat characteristics of each nest site, they found little evidence that the wind energy facility affected nest site selection or a nest’s chances of survival. Instead, vegetation characteristics, driven by land use practices such as grazing, had the greatest influence on prairie-chicken nests. Birds also avoided nesting near roads.

“When comparing previous studies to our own, it appears that the effects of wind energy facilities on prairie grouse are often site- and species-specific,” says Harrison. “Therefore, it’s important to consider the results of our study in the context of the size and location of the wind energy facility, as well as the prairie grouse species investigated. We suggest that livestock grazing and other grassland management practices still have the most important regional effects on Greater Prairie-Chickens, but we caution future planners to account for potential negative effects of roads on nest site placement.”

Private landowners were key to completing the study, Harrison adds. “Our radio- and satellite-tagged Greater Prairie-Chickens made larger than expected movements while we were tracking them, which led us to require permission from new land owners on almost a weekly basis during our field seasons. Landowners throughout our field study area were always extremely welcoming and helpful, and genuinely interested in our work. Our project was a success due to more than 50 landowners who granted us access to their private lands.”

Nest site selection and nest survival of Greater Prairie-Chickens near a wind energy facility is available at http://www.bioone.org/doi/full/10.1650/CONDOR-17-51.1.

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.

Fifty Years On, the Breeding Bird Survey Continues to Produce New Insights

Special Collection of Research Papers Highlights Latest Findings

CONDOR BBS W A Link

Prothonotary Warblers (Protonotaria citrea) inspect a possible nest site at the Patuxent Wildlife Research Center, Laurel, Maryland. Prothonotary Warblers are one of more than 500 species monitored by the North American Breeding Bird Survey. Photo credit: W.A. Link

In 1966, a U.S. Fish and Wildlife Service biologist named Chan Robbins launched an international program designed to measure changes in bird populations using volunteers recruited to count birds on pre-set routes along country roads. The result, the North American Breeding Bird Survey or BBS, is still going strong more than five decades later. This month The Condor: Ornithological Applications is publishing a special set of research papers to honor the program’s fiftieth anniversary.

Unassuming but visionary, Robbins had studied DDT’s effects on birds—his reports were edited by Rachel Carson—and he wanted to devise a way of monitoring the health of the continent’s bird populations on a large scale. The simple field protocols he developed, able to be carried out by volunteer birdwatchers, have remained largely the same since the program’s inception. Today, there are more than 4100 survey routes spanning North America from Alaska to Newfoundland, Florida, and northern Mexico.

The BBS provides long-term data for 424 species, with more limited data for an additional 122. Since data collection began in the 1960s, significantly more species have been declining than increasing. Looking at patterns of change in groups of birds sharing common attributes can be especially useful; for example, only 8 of 24 grassland bird species have seen increases. However, in the short term the picture is slightly rosier—since the survey area was expanded in 1993, 56% of the species surveyed have showed positive trends. Today, modern statistical techniques are letting ornithologists glean more insight from BBS data than ever before.

“The BBS is the only source of long-term, multi-scale population change information for more than 500 species of North American birds,” according to the USGS’s John Sauer, who has worked with the BBS since 1986 and was one of the co-editors for the special section along with Keith Pardieck and Colleen Handel, also with the USGS. “BBS results have allowed conservationists to identify bird species and regions undergoing population declines, alerting the public and scientists to population changes and facilitating the development of initiatives to better understand declines.”

The papers that make up the special section in The Condor include:

  • Prioritizing areas for conservation by combining six years of BBS data with remotely sensed environmental data to model the predicted distribution of seven grassland bird species in the Northern Great Plains based on their habitat needs.
  • Statistical approaches for model selection in BBS analyses.
  • Combining BBS with off-road surveys to estimate population changes for birds that breed in Alaska, where habitats are being rapidly altered due to climate change.
  • Using long-term BBS data to rank the vulnerability of more than 460 landbird species, set population objectives, and track progress toward meeting conservation goals.
  • Analyzing how well road-based BBS routes represent larger landscapes, using data from 2011 National Land Cover Database, with the conclusion that any land-cover–based roadside bias in BBS data is likely minimal.
  • Combining BBS data with separate demographic data to estimate the size of the Atlantic Flyway’s Wood Duck population.
  • Plus, a review of how the BBS has informed North American bird conservation since its inception.

The papers grew out of a research symposium held at last summer’s North American Ornithological Conference in Washington, DC, to commemorate 50 years of the BBS. “The BBS provides a fundamental tool for understanding breeding bird distribution and abundance. We’re pleased to publish these papers that celebrate Chan Robbins’s vision and the hard work of thousands of volunteers through the latest results and analyses,” said Philip Stouffer, Editor-in-Chief of The Condor: Ornithological Applications.

The special section on the Breeding Bird Survey is available at http://www.bioone.org/toc/cond/119/3.

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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Seaside Sparrows Caught Between Predators and Rising Seas

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Fledgling Seaside Sparrows. Photo credit: E. Hunter

Sea-level rise may be a big problem for salt marsh birds, but so is predation, and birds sometimes find themselves caught between a rock and a hard place: They can place their nests lower in the vegetation to avoid predators, putting them at greater risk of flooding, or move them up to keep them dry but risk getting eaten. A new study from The Condor: Ornithological Applications finds that greater pressure from predators increases the risk of flooding for Seaside Sparrow nests—but the upside is that protecting them from predators could also mitigate the worst effects of climate change.

The University of Georgia’s Elizabeth Hunter (now at the University of Nevada–Reno) created a mathematical model to simulate Seaside Sparrow’s nesting behavior and success rates, based on nesting data collected on the coast of Georgia.  Her model shows that predation risk has had a much greater effect than flooding risk on nest survival rates. While flooding risk had essentially no effect on predation rates over this time period, predation risk did affect flooding rates—that is, because birds moved their nests down to avoid predators, they increased their risk of flooding. Under future sea level rise scenarios, flooding risk increases, but predation risk is still almost seven times as important for determining nest survival rates.

“Nest predation rates are so high right now that even under extreme sea level rise conditions, more nests are likely to be eaten than flooded,” says Hunter. “However, predation and flooding threats act synergistically, meaning that any estimates of the negative effects of sea level rise on the nesting success of Seaside Sparrow or other species are likely underestimates if they do not also consider the negative effects of predation on flooding risk. The flip side of this is that management actions to reduce nest predation could also reduce the risk of nest failures from flooding.” If measures such as fencing nest sites to exclude predators are taken, birds may place their nests higher in the salt-marsh vegetation, avoiding flooding from extreme high tides.

“Elizabeth Hunter’s research highlights both the risks that sea-level rise poses for coastal wildlife and the complexity of understanding those risks in light of other threats to their survival,” according Chris Elphick of the University of Connecticut, an expert on tidal marsh birds who was not involved with the study. “The study nicely illustrates the importance of understanding the behavior of individual birds when trying to devise strategies to mitigate threats such as predation and tidal flooding. Regardless of the threat, it is increasingly clear that tidal marsh birds and their habitats are in trouble, and that we need to explore a range of potential solutions to find ways to help them persist in light of the many ways that humans are changing coastal habitats.”

How will sea-level rise affect threats to nesting success for Seaside Sparrows? is available at http://www.bioone.org/doi/abs/10.1650/CONDOR-17-11.1.

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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Birds’ Feathers Reveal Their Winter Diet

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

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

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

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

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

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

Winter diet of Bobolink, a long-distance migratory grassland bird, inferred from feather isotopes is available at http://www.bioone.org/doi/full/10.1650/CONDOR-16-162.1.

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.

2016 Journal Impact Factors Released

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

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

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Radar Reveals Steep Declines in Kauai’s Seabird Populations

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

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

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

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

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

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

Declining population trends of Hawaiian Petrel and Newell’s Shearwater on the island of Kaua’i, Hawaii, USA is available at http://americanornithologypubs.org/doi/abs/10.1650/CONDOR-16-223.1.

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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AUTHOR BLOG: Tracking Yosemite’s Spotted Owls

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

Stephanie Eyes

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

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

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

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

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