If you build it, the birds will come—if it meets their criteria

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California Gnatcatchers need more than just the right vegetation. Photo credit: A. Fisher

A study published in The Condor: Ornithological Applications presents a case study on how bird surveys can better inform conservation and vegetation restoration efforts. Previous conservation methods have emphasized plants as the key to recreating habitat preferred by a sensitive animal. However, this study shows that there’s more to the coastal sagebrush habitat of California Gnatcatchers than just having the right plants present. Abiotic components such as topography and soil are important drivers of the biotic components, including plants, which pair together to make the complete ecosystem these birds need. Given this more complete perspective, future conservation efforts would be wise to consider all of the variables that make up an animal’s habitat.

The U.S. Fish and Wildlife Service’s Clark Winchell and Colorado State University’s Paul F. Doherty, Jr., set out to find a way to improve the traditional “single-species-oriented” conservation plan. They used bird survey data to more accurately identify favorable habitat for California Gnatcatcher occupancy and discovered that as the ratio of coastal sagebrush increased from 10% to 40%, the probability of colonization and presence of these birds tripled. The amount of openness in the sagebrush habitat also correlated with the birds’ occupancy probability (30-40% openness was ideal for the birds). Elevation and soil texture also influenced suitable habitat, with lower elevations and loam or sandy loam soils most preferred. Winchell and Doherty also found that the gnatcatchers preferred southern aspects, shallow slopes, and inland areas over other options. Being so detailed and using such a fine scale allowed more specific areas to be identified as suitable for gnatcatchers. Thorough research such as this will better aid conservation efforts, both by informing where restoration might be most successful and by providing restoration targets.

Winchell comments, “Restoration ecologists are generally not gnatcatcher biologists, and vice versa. Sometimes we tend to place restoration projects where land becomes available after political negotiations. We may want to consider what is that parcel of land trying to tell us—what does the land want to be, so to speak—versus assuming we can dictate the final outcome for a location. Considering the entire functionality of the surrounding ecosystem, including the physical components, the biological community, and understanding the dynamism of the ecosystem will lead to improved restoration and wildlife management outcomes and our study is one small step in that direction.”

These results correlating soil, vegetation, and gnatcatcher occupancy harken back to lessons that Aldo Leopold taught us—namely, to start with the land and work with the land when managing wildlife. Leopold’s holistic approach to conservation included the soils, waters, plants, and animals and is still relevant today.

Restoring habitat for coastal California gnatcatchers (Polioptila californica californica) is available at http://www.bioone.org/doi/full/10.1650/CONDOR-17-221.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology, published by the American Ornithological Society. For the past two years, The Condor has had the number one impact factor among 27 ornithology journals.

Rainy weather predicts bird distribution—but climate change could disrupt it

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Precipitation is the best predictor of Eastern Kingbirds’ winter distribution. Image credit: M. MacPherson

Understanding what environmental cues birds use to time their annual migrations and decide where to settle is crucial for predicting how they’ll be affected by a shifting climate. A new study from The Auk: Ornithological Advances shows that for two species of flycatcher, one of the key factors is rain—the more precipitation an area receives, the more likely the birds are to be there during the non-breeding season.

Tulane University’s Maggie MacPherson and her colleagues combined field techniques with species distribution models to investigate which environmental factors drove the migrations of Eastern Kingbirds and Fork-tailed Flycatchers. Using geolocators, devices that record a bird’s daily location based on day length, they could track where individuals of each species went. The two species share similar behavior and habitat requirements, but differ in their range and migration strategies, and these strategies were compared to determine the influence of temperature, precipitation, and primary productivity (the amount of “green” vegetation). Precipitation turned out to be one of the most important predictors of their distribution, particularly in the non-breeding season.

MacPherson comments, “Although we understand how climate change is expected to affect regional temperature regimes, changes in patterns of seasonal precipitation remains unclear. As the locations of both species were positively correlated with the highest rainfall across the landscape during their non-breeding seasons, our research emphasizes the need for a better understanding of how flexible they may be in adjusting locations under new rainfall regimes. More research is needed to better understand how migratory birds relying on current rainfall regimes could benefit from climate-conscious conservation planning.”

“In the face of climate change, having seasonal species distribution models like these is powerful for helping understand the biology of the species, and also for predicting how a population might change in size and geography in the future, or a species’ flexibility to adjust its migratory timing,” adds Mississippi State University’s Auriel Fournier, an expert on species distribution models who was not involved in the study. “All of those predictions are vital for conservation planning and decision making. The use of two related species with different life history traits is also exciting, as it makes the results more broadly applicable.”

Follow the rain? Environmental drivers of Tyrannus flycatcher migration across the New World is available at http://www.bioone.org/doi/full/10.1642/AUK-17-209.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology published by the American Ornithological Society. The Auk commenced publication in 1884, and in 2009 was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

Piping Plovers want people to get off their lawn

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Banded Piping Plover in non-breeding plumage (Photo Credit: Kelley Luikey)

A new study in The Condor: Ornithological Applications presents negative associations between anthropogenic disturbance (human recreational use of beaches, coastal modifications) and Piping Plovers on their non-breeding grounds. Shorebirds are one of the most threatened bird families in the world. Numerous studies have shown the negative impacts of humans on these birds, whether it be large-scale (e.g., habitat loss, climate change) or small-scale (e.g., ATV use, running with pets, flying kites). This research indicates that there are direct consequences of disturbance. Most Piping Plover research has focused on the breeding season in an attempt to directly influence population numbers, however this study argues that efforts are required throughout the year in all locations to assist Piping Plover conservation.

Virginia Polytechnic Institute and State University’s Dan Gibson and colleagues monitored Piping Plovers year-round to determine the health and behavior of individuals. Body condition, survival, and site fidelity were of most interest. Plovers in disturbed areas proved to be significantly lighter in mass, due to the birds not procuring enough food. Given poorer body condition, it should be no surprise that birds in these disturbed areas also had lower survival rates. Piping plovers have strong site fidelity on the breeding grounds and this study supports that fidelity continues on the non-breeding grounds. While physically capable of changing location, it was not common for individuals to do so even if there was a high level of disturbance. The lack of movement by disturbed individuals suggests that aspects of the species’ life history (i.e. fidelity) constrained individuals to make seemingly adaptive habitat-use decisions. Some of the strategies used on the breeding grounds (reduced human recreation, roped-off areas, no dogs on beaches) may be beneficial to also do on the non-breeding grounds to ensure year-round conservation and oversight on this threatened shorebird species.

Lead author Dan Gibson comments, “We have a lot of of opportunity to engage with the public in what exactly our research is about. We often try to stress that the impact an individual recreationist has on a shorebird is practically non-existent. However, if every person who uses a beach in a given day influences how these shorebirds feed or rest, those minute impacts can begin to add up over the course of a season that can manifest itself as reductions in individual body condition and ultimately their ability to withstand bad weather conditions or successfully migrate and find a mate. We try to stress that small changes in how we use a beach (e.g., keep dogs on leash, avoid running through groups of birds) can really add up to substantial improvements in the overall quality of coastal habitat for shorebirds.”

“This study availed itself of a unique resource that range-wide banding efforts have provided for the study of the demographics of the endangered piping plover,” adds College of Environmental Science and Forestry Associate Professor Jonathan Cohen, a shorebird expert who was not involved with the research, “and successfully attempted the difficult task of teasing out the sometimes subtle effect of disturbance in nonbreeding areas on annual vital rates.  The finding that this endangered species may not readily abandon habitat that is detrimental for fitness was surprising, and warrants immediate attention from the conservation community.”

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Impacts of anthropogenic disturbance on a non-breeding shorebird’s body condition, survival, and site fidelity is available at http://www.bioone.org/doi/full/10.1650/CONDOR-17-148.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology published by the American Ornithological Society. The journal began in 1899, and in 2016 The Condor had the number one impact factor among 24 ornithology journals.

Crows are always the bullies when it comes to fighting with ravens

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Three Crows (left) versus one Raven (right) (Photo credit: PhillipKrzeminski)

A study from The Auk: Ornithological Advances presents citizen science data which supports that American Crows and Northwestern Crows almost exclusively (97% of the time) instigate any aggressive interactions with Common Ravens no matter where in North America. The data showed that aggression by crows was most frequent during the breeding season, most likely due to nest predation by ravens. This study not only gives insight into interspecies dynamics, but also how citizen science data can aid behavioral studies at large geographic scales.

Cornell University’s Ben Freeman and colleagues used more than 2,000 publicly collected and submitted observations from across North America via eBird to analyze the interspecific aggression between crows (American and Northwestern) and Common Ravens. From these records, it was determined that crows were the predominant aggressor. Crows primarily attacked in small groups rather than one-on-one confrontations with ravens. The breeding season was when most of the attack observations were made, suggesting that nest predation by ravens influences this behavior. Aggression during the winter is potentially explained by crows preemptively deterring nest predation and defending resources needed for nesting later in the year. This study was made possible by citizen scientists who were not even asked to submit such observations. Given this was passively collected data that aided in a behavioral study on a large geographic area, it could act as a model for other research and potential studies conducted.

Lead author Ben Freeman comments, “There are two take-home messages. First, we show that bigger birds do not always dominate smaller birds in aggressive interactions, and that social behavior may allow smaller birds to chase off larger birds. Second, this is a case example of the power of citizen science. It would be next to impossible for even the most dedicated researcher to gather this data across North America. But because there are thousands of people with expertise in bird identification and an interest in bird behavior, we can use data from eBird to study behavioral interactions on a continental scale.”

“Given that aggression between crows and ravens can be quite conspicuous, birders and the general public are often the observers of such interactions,” adds Kaeli Swift of the University of Washington, who was not involved with the research, “yet despite the ease and frequency of witnessing these events, there was little scientific information for curious minds to turn to for explanation. It’s quite rewarding then, that the citizen scientists that may have wished for this information are the very people whose observations made this publication possible.

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Why do crows attack ravens? The role of predation threat, resource competition and social behavior is available at http://www.bioone.org/doi/full/10.1650/AUK-18-36.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology published by the American Ornithological Society. The Auk commenced publication in 1884, and in 2009 was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

To help save Northern Spotted Owls, we need to prevent kissing cousins

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Spotted Owl (Photo Credit: Alan Dyck)

The Auk: Ornithological Advances presents a study on a Northern Spotted Owl pedigree, consisting of almost 14,200 individuals over 30 years, which determined inbreeding varies across the species’ range. Selection against inbreeding based on decreased future reproduction, fewer offspring, and overall survival of individuals was also supported. These results indicate that Spotted Owl conservation efforts need to address owl breeding more. Another implication of this work is the need to increase genetic diversity to prevent further population decline.

Mark Miller of the United States Geological Survey (USGS) Forest and Rangeland Ecosystem Science Center, and colleagues employed field and statistical methods to create a family tree for Northern Spotted Owls living in California, Oregon, and Washington. From this, the researchers determined how often inbreeding occurs in the wild for these birds. Fourteen types of matings among relatives were determined with most inbreeding relationships being between half or full siblings. It was discovered that inbreeding is most common in the Washington Cascades (~15% of individuals are inbred), while the lowest inbred population was Northern California (~2.7% of individuals). The explanation for this geographic variation may be the rate at which specific populations are declining and experiencing bottlenecks. Conservation efforts are vital today given that Northern Spotted Owls are already facing habitat loss and competition with a similar species, the Barred Owl. This study showed that both the physical consequences of inbreeding (physical deformities, reduced ability to adapt) and the reproductive fitness of individual birds (infertility, future reproduction, decreased survival) need to be taken into account since both influence this species’ success. Translocating birds among populations to help increase the genetic diversity may be a potential management strategy.

Lead author Mark Miller comments, “Long-term studies, similar to the one described in this paper, are key to understanding how common or rare inbreeding is in natural populations. An understanding of the extent of inbreeding can help resource managers better identify appropriate measures to conserve threatened and endangered species.”

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Variation in inbreeding rates across the range of Northern Spotted Owls (Strix occidentalis caurina): Insights from over 30 years of monitoring data is available at http://www.bioone.org/doi/full/10.1650/AUK-18-1.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology published by the American Ornithological Society. The Auk commenced publication in 1884, and in 2009 was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

Terns Face Challenges When They Fly South for Winter

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A Common Tern wearing a geolocator. Photo credit: C. Henderson

The Common Tern is most widespread tern species in North America, but its breeding colonies in interior North America have been on the decline for decades despite conservation efforts. The problem, at least in part, must lie elsewhere—and a new study from The Auk: Ornithological Advances presents some of the best information to date on where these birds go when they leave their nesting lakes each fall.

The University of Minnesota’s Annie Bracey and her colleagues attached geolocators—small, harmless devices that record a bird’s location over time based on day length—to 106 terns from breeding colonies in Manitoba, Ontario, Minnesota, Wisconsin, and New York. When the birds returned to their breeding grounds in the following years, the researchers were able to recapture and retrieve data from 46 birds. The results show important migratory staging areas in the inland U.S. and along the Gulf of Mexico—a surprise, since it was previously thought that most Common Terns head for the Atlantic coast before continuing south. Birds from different colonies intermingled freely in the winter, but most ended up on the coast of Peru, suggesting that the population could be especially vulnerable to environmental change in that region.

For long-lived birds such as Common Terns, adult survival likely drives population trends more than breeding productivity, so identifying causes of mortality is crucial for effective conservation. Coastal Peru is vulnerable to multiple effects of climate change, including increasingly frequent and severe storms, changes in the availability of terns’ preferred foods, and rising sea levels. “Because survival is lowest during the non-breeding season, identifying coastal Peru as a potentially important wintering location was significant, as it will help us target studies aimed at identifying potential causes of adult mortality in this region,” says Bracey.

“This paper is both important and interesting, because it takes a species we consider ‘common’ and examines the reasons for its decline,” adds Rutgers University Distinguished Professor of Biology Joanna Burger, a tern conservation expert who was not involved in the research. “In short, this is one of the first studies that examines the entire complex of terns breeding in inland US locations, along with migratory routes, stopover areas, and wintering sites. It vastly increases our knowledge of the causes of declines and the locations and times at which terns are at risk, and more importantly, provides a model for future studies of declining populations.”

Migratory routes and wintering locations of declining inland North American Common Terns is available at http://www.bioone.org/doi/full/10.1642/AUK-17-210.1.

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.

Long-Term Study Reveals Fluctuations in Birds’ Nesting Success

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Long-term data on Song Sparrows reveals factors that affect their nesting success. Photo credit: D. Janus

Understanding the factors that affect a bird species’ nesting success can be crucial for planning effective conservation efforts. However, many studies of nesting birds last only a few years—and that means they can miss the effects of long-term variation and rare events. A new study from The Auk: Ornithological Advances demonstrates this with nearly four decades of data from Song Sparrows in British Columbia.

The University of British Columbia’s Merle Crombie and Peter Arcese used 39 years of data from an island population of Song Sparrows to examine how the factors influencing their nesting success changed over long periods of time. Over almost 3,000 nesting attempts, 64% of which were successful, a number of patterns emerged. Some, such as the fact that older female birds were less successful, remained consistent over time. However, others, such as the effects of rainfall, population density, and nest parasitism, interacted with each other in complex ways that caused their importance to wax and wane over the decades, and inbreeding only became a significant negative factor when it increased sharply during the middle portion of the study. Unpredictable, rare fluctuations such as this can have large effects that shorter-term studies rarely capture.

“Researchers have been learning about the Song Sparrow population on Mandarte Island since 1960, and monitoring the population continuously since 1975,” says Arcese. “Because the population is semi-isolated, small, and resident year-round, we band all birds in the nest and have genotyped all nestlings since 1991.” A close focus on individuals, fitness, and relatedness in the Mandarte Song Sparrow population has allowed researchers to report the most precise demographic and population genetic parameters yet estimated in wild populations.

“Most studies of plant and animal populations in nature last three to five years, but ecological processes are often dramatically affected by climate and community change, which plays out over decades,” he continues. “Long-term studies like ours provide an invaluable record of change in population processes, which can help interpret the results of short-term studies of species not as easily studied as Song Sparrows.”

Temporal variation in the effects of individual and environmental factors on nest success is available at http://www.bioone.org/doi/full/10.1642/AUK-17-189.1.

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.