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Research From The Auk and The Condor

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The official blog of ornithology journals The Auk and The Condor
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The American Ornithological Society to partner with Oxford University Press to publish The Auk and The Condor

Wed, 07/18/2018 - 10:10

Big news! Beginning in 2019, The Auk and The Condor will be moving to a new publishing partner, Oxford University Press. Read the full announcement here: https://amornithnews.org/2018/07/18/oup-to-publish-auk-and-condor/

AUTHOR BLOG: Ancient Fossil Bones of a Recently Extinct Cormorant

Wed, 07/11/2018 - 10:01

Junya Watanabe

Linked paper: Pleistocene fossils from Japan show that the recently extinct Spectacled Cormorant (Phalacrocorax perspicillatus) was a relict by J. Watanabe, H. Matsuoka, and Y. Hasegawa, The Auk: Ornithological Advances 135:4, October 2018.

Live reconstruction of the Spectacled Cormorant from study skins. Artwork by Joseph Wolf, from Elliott (1869), The New and Heretofore Unfigured Species of the Birds of North America, Volume 2.

Numerous extinction events have taken place in geologically recent time, caused to varying degrees by human activity. Although relatively much is known about how humans have given “final blows” to animal species in recent history, little is known about the long-term biogeographic and evolutionary history of extinct animals. This is where archaeological and fossil records play crucial roles. One of the most (in)famous examples of historic extinctions is the case of the Great Auk, which was once widespread in the North Atlantic Ocean but was driven to extinction in the mid-19th century due to hunting by humans. There is one potential parallel, though less widely known, in the North Pacific Ocean; a large seabird species called Spectacled Cormorant (Phalacrocorax perspicillatus) was driven to extinction almost contemporaneously. This species was first discovered in the 18th century on Bering Island, part of the Commander Islands, by German explorer Georg Steller, who became the only naturalist to observe the birds in life. Following the colonization of the island by humans in the early 19th century, this species was hunted by humans, and it was driven to extinction in the 1850s. As there has been no record of the species outside Bering Island, it is considered to have been restricted to the island throughout its existence. Our new study in The Auk: Ornithological Advances, however, reports the first definitive record of the cormorant species outside Bering Island, demonstrating that the species was in fact not restricted to the island in the past.

Through our study of Japanese fossil birds, my colleagues and I identified 13 fossil bones of the Spectacled Cormorant from upper Pleistocene deposits (dated ~120,000 years ago) in Japan. The fossil bones were recovered from Shiriya, northeastern Japan, through excavations led by my co-author Yoshikazu Hasegawa of the Gunma Museum of Natural History. Through detailed examination of the bird fossils from the site, it became evident that a cormorant species much larger than any of the four native cormorant species in present-day Japan was represented in the material. At first, we suspected the presence of a new species, but this turned out not to be the case. Through a literature survey, I came across a 19th-century paper by American ornithologists Leonhard Stejneger and Frederic Lucas that described bones of the Spectacled Cormorant collected on Bering Island. The dimensions and illustrations given in the paper were strikingly similar to the Japanese fossils. I decided to visit the Smithsonian Institution’s National Museum of Natural History in Washington, D.C., where the bones described by Stejneger and Lucas are stored. After careful examination, the Japanese fossils turned out to agree in every detail with bones of the Spectacled Cormorant from Bering Island, rather than with any other species compared, to the extent that I was convinced that the Japanese fossils belong to the same species as the Bering Island bones.

The occurrence of the Spectacled Cormorant from Japan is the first definitive record of this species outside Bering Island and indicates that the species underwent a drastic range contraction or shift since the Pleistocene. In other words, the population of this species on Bering Island discovered by Steller was in fact a relict, with most of the species’ past distribution already lost. Changes in oceanographic conditions might be responsible for the local disappearance of the species in Japan; paleoclimate studies have shown that the oceanic productivity around Shiriya dropped drastically in the Last Glacial Maximum (~20,000 years ago), which would have seriously affected the population of the species. Although it might be possible that hunting of that species by humans took place in prehistoric Japan, no archaeological evidence for that is known so far. The entire picture of the recent extinction event of the Spectacled Cormorant might be more complex than previously thought, as is becoming evident for some other extinct seabirds in other parts of the world.

Further reading

Fuller, E. (2001). Extinct Birds, revised edition. Cornell University Press, New York, NY.

Hume, J. P. (2017). Extinct Birds, 2nd edn. Bloomsbury Natural History, London.

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

Wed, 07/11/2018 - 09:49

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

Wed, 07/11/2018 - 09:45

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

Wed, 07/04/2018 - 09:26

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

Wed, 07/04/2018 - 09:25

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

Wed, 07/04/2018 - 09:25

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.

It’s go time for Hawaiian bird conservation, and luckily there’s a playbook

Thu, 06/28/2018 - 16:56

‘I’iwi (Photo credit: Lucas Behnke)

A new study in The Condor: Ornithological Applications presents some of the best guidance to date on the priorities and actions that can be taken to help Hawaii’s endemic birds. Hawaii’s ecosystems, including its native bird populations, are struggling. Of the 21 species of forest birds left on the islands, almost two thirds (12 species) of are endangered or threatened. The current conservation status of the wildlife and vegetation on the island is almost entirely attributable to humans. The actions needed to stabilize or reverse these trends need stronger support and coordination, however funding and resources are limited. This new paper lays out a plan to better guide and empower conservation efforts for Hawaiian birds.

Eben Paxton of USGS Pacific Island Ecosystems Research Center and colleagues synthesized the key points that came out of a collaboration of more than 60 stakeholders in Hawaiian bird conservation. The focus is on actionable research and management approaches that can be employed today. Habitat loss, invasive plants, non-native predators, and introduced diseases were identified as the largest threats to Hawaiian birds. Climate change is projected to exacerbate all threats. Given limited resources, the stakeholders decided on eight main priorities as well as several actions specific to the island of Kauai. In addition to helping Hawaii and its birds directly, the goal of this collaborative report is to make Hawaii a model for other areas of the world, especially islands, that are in need of strong conservation efforts.

Lead author, Eben Paxton comments, “Our challenge in Hawaii is how do we conserve forest birds from multiple threats with just a fraction of the resources needed to fully address all the threats. Our solution was to bring researchers and managers together to share ideas, and as a community, identify priority research and management needs necessary to save these unique species. We believe these priorities will help focus resources where most needed and bring together different organizations to work together for the maximum benefit of the birds.”

“New Technology is being proposed to help stem the tide of extinctions in Hawaiian native birds. Eben Paxton and his co-authors recognize that all the native birds in Hawaii are Conservation Reliant Species and propose utilizing new technologies to assist with the preservation of this unique island avifauna,” adds Charles van Riper III, a ST Research Ecologist and Professor Emeritus, USGS and SNRE, University of Arizona. “This very complete paper also recommends enhancing Citizen Science and captive breeding in the Islands, along with continued monitoring and translocations to unoccupied habitat. The immediate target for this plan are the birds on Kauai – the authors feel that the native avifauna on this island is rapidly approaching extinction, and time will tell how successful this proposed plan is in implementing conservation actions in time to save these unique birds.”

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Research and management priorities for Hawai’i forest birds is available at http://www.bioone.org/doi/full/10.1650/CONDOR-18-25.1.
Research contact: Eben Paxton, epaxton@usgs.gov

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.

 

When You’re a Sitting Duck, You Learn to Adapt

Wed, 06/20/2018 - 12:15

Common Loon on nest dealing with black flies (Photo credit: Linda Grenzer)

When sitting on a nest to incubate eggs, a bird is physically stuck and most vulnerable to attacks of any kind, so coping without stress and other significant costs is important. For Common Loons, black flies are a common blood-feeding pest and can cause nest abandonment and decreased fledging rates. This has impacts on not only individual pair success, but on population dynamics as well. A new study from The Auk: Ornithological Advances presents some of the best data to date supporting hypotheses about the effects that black flies have on Common Loon nesting behavior and success.

Chapman University’s Walter Piper and colleagues monitored Common Loon nests for 25 years in northern Wisconsin, USA. They marked individuals to track each bird’s behavior, nesting success, and interaction with black flies. More than 2,050 nests were included in the study to apply the impacts of black flies on loons’ population level. If the black fly concentration around an individual bird was high or there was a particularly intense fly outbreak year, loon incubation time decreased and nest abandonment increased. It was discovered that nest abandonment could be predicted using lake size, female age, and wind. The team found that the smaller the lake, the older the female, and the greater the distance across water that wind has to travel to reach the nest the more likely the nest will be abandoned. The cost associated with severe black fly outbreaks appears to be high enough that a nest can be abandoned and a second attempt made following the peak of the outbreak. The second nest is likely to be in the original location unless a predator destroyed the nest. In that case, the pair is more likely to choose a new and hopefully safer nest site.

Lead author Walter Piper comments, “Black flies, which we think of as a nuisance and no more, actually impact population reproductive success. This was a matter of studying an animal for 25 years and almost ignoring one aspect of their biology — until you finally look straight at that aspect of biology and realize it’s crucially important! Loons get slammed by black flies, but they make a very good response by reusing the nest sites where the flies hounded them, instead of abandoning those sites altogether — as they do when raccoons get their eggs. This makes sense, because the raccoons are their main enemies (that is, egg predation is a more severe problem then black flies), and a safe nesting site from raccoons is a vital resource.”

“This study is one of the first that examines the negative influence of black flies on a population of birds rather than on individuals alone. Perhaps more importantly, by studying a marked population of loons for almost a quarter century, it is possible to determine the stochastic influence of black fly outbreaks on the population as well as understand the nuances of how these mechanisms might work,” adds Jeb Barzen, an ecologist with Private Lands Conservation, who was not involved with this study. “Black flies severely reduce reproductive effort of loons periodically but not every year, a finding that is important to understanding the population dynamics of this iconic species. The more subtle examination of individual response to black flies provides insight into differences in how males and females, as well as individuals in different habitats and individuals of different ages, respond to black fly infestations. Collectively these results inform ecologists and managers alike in issues relevant to the conservation of loon populations and other long-lived, territorial bird species.”

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Common Loons respond adaptively to a parasite that impacts nesting success is available at http://www.bioone.org/doi/full/10.1642/AUK-17-239.1
Researcher contact: Walter Piper, wpiper@chapman.edu

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.

Original habitat is best, but restoration still makes a big difference

Wed, 06/13/2018 - 07:41

Yellow-breasted Chat nest with chicks. (Photo Credit: Melissa C. Roach)

A new study in The Condor: Ornithological Applications presents some of the best evidence to date that restoration efforts in Missouri’s Ozark Highlands make a difference for nesting songbirds that breed there. The reduction of Missouri pine savannah and woodland areas has caused birds that rely on these habitats to decline. Current efforts to bring these habitats back are under way and include prescribed fire and thinning tree stands. Recent studies support that these efforts are making a positive impact on the ecosystem and increasing the survival of bird species that breed there.

Melissa Roach of the University of Missouri and colleagues investigated the relationship between daily nest survival and habitat and restoration efforts. Her team studied six species comprising two groups: shrub-nesters and canopy-nesters. Eastern Towhee, Prairie Warbler, and Yellow-breasted Chat were representative of shrub-nesting species, while canopy-nesting species included Eastern Wood-Pewee, Pine Warbler, and Summer Tanager. After monitoring nests for two years, researchers found that predation was the number one cause of nest failure. Current restoration efforts (fire and tree thinning) directly influenced the ground layer of vegetation. This changed the cover available to both hunting predators and hiding prey, changing the predator–prey dynamics. Thus, restoration efforts and maintaining a varied landscape for wildlife is important for the success of these songbirds.

Lead author Melissa Roach comments, “We found strong results that should help guide land managers when it comes to important management decisions regarding the restoration and maintenance of rare or sensitive habitats. Not only were we able to show that these species are responding positively to pine woodland restoration, we provided baseline nest survival data for some understudied species. We also hope that this study increases the public’s awareness and appreciation of just how important prescribed fire and tree thinning can be for wildlife.”

“As the Coordinator of the Central Hardwoods Joint Venture, the regional partnership guiding bird conservation across the Ozarks and Interior Low Plateaus ecoregions, I find it gratifying to see research showing that the restoration of fire-dependent natural communities like shortleaf pine woodlands has such a positive effect on populations of bird species of conservation concern,” adds Jane Fitzgerald, of the American Bird Conservancy and Central Hardwoods Joint Venture Coordinator. “While we have, in the past, focused much of our planning on increasing carrying capacity by increasing the amount of high-quality habitat available to a species, we are learning that it’s just as important to evaluate how management impacts the vital rates that drive population growth. I hope we see more and more research that provides that kind of ‘big picture’.”

 

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Songbird nest success is positively related to restoration of pine–oak savanna and woodland in the Ozark Highlands, Missouri, USA is available at http://www.bioone.org/doi/full/10.1650/CONDOR-17-189.1.
Research contact: Melissa C. Roach, roach.mc1@gmail.com

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.

For Disappearing Bicknell’s Thrushes, Statistical Models are Lifesavers

Wed, 06/06/2018 - 08:38

Bicknell’s Thrush (Photo Credit: Steve Faccio)

Bicknell’s Thrush has been identified as a globally vulnerable Nearctic-Neotropical migratory bird in need of serious conservation efforts. This species travels each year between its breeding grounds in the Canadian maritime provinces and upper northeastern United States and its winter home in the Greater Antilles. Males and females use different habitats in winter, with females preferring middle elevation forests that are more vulnerable to human disturbance than the higher, more remote forests used by males.   A new study from The Condor: Ornithological Applications identifies key habitat for females in the remaining fragmented montane wet forests of the Dominican Republic.

“Today’s multiple environmental threats and stressors (e.g., deforestation, predation by invasive species, climate change, bioaccumulation of heavy metal pollutants, etc.) are crafting an uncertain future for species with complex life cycles in their breeding grounds, stopover sites, and wintering grounds,” adds Eduardo E. Ingio Elias, a senior research associate of the Cornell Lab of Ornithology who was not involved with this research. “However, to conserve key suitable habitat for any species, ornithologists and land managers need to identify where that habitat is, what the population survival is within that habitat, and what threats birds face there.”

Vermont Center for Ecostudies scientist Kent McFarland and colleagues used a combination of field and GIS methods to predict areas that would be the best to conserve for Bicknell’s Thrushes. A model to predict Bicknell’s Thrushes’ distribution and habitat use was created using occurrence data and environmental variables collected from field surveys, combined with land cover data from remote sensing. Thrush presence and abundance in an area was best predicted by the combination of elevation (densities peaked at ~600 m), aspect (northeastern slopes), the amount of forest cover within 1 km, and forest density.

Lead author Kent McFarland emphasizes the importance of this work, which has demonstrated putting research into conservation action, “We used our results to help identify, purchase, and create the Dominican Republic’s first-ever private reserve, the 400-ha Reserva Privada Zorzal, where 70% of the land is to be forest and ‘forever wild’ while the remainder is for compatible crops such as organic chocolate. We are hoping that our work will be used to identify and prioritize additional lands for conservation of the Bicknell’s Thrush in the region and elsewhere.”

 

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Modeling spatial variation in winter abundance to direct conservation actions for a vulnerable migratory songbird, the Bicknell’s Thrush (Catharus bicknelli) is available at http://www.bioone.org/doi/full/10.1650/CONDOR-17-234.1.
Research contact: Kent McFarland, kmcfarland@vtecostudies.org

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.

For flickers, looks can be deceiving

Wed, 06/06/2018 - 07:24

Red-shafted Flicker (Photo Credit: Glenn Lahde)

The North American woodpeckers known as “flickers” stand out for their distinctive wing and tail feathers of bright reds or yellows, and for their rampant interbreeding where these birds of different colors meet in the Great Plains. Despite the obvious visual differences between the Red-shafted Flicker of the west and the Yellow-shafted Flicker of the east, scientists have never before found genetic differences between them. A new study from The Auk: Ornithological Advances uses data from thousands of regions across the genome to distinguish these birds molecularly for the first time.

Stepfanie Aguillon and her colleagues at the Cornell Lab of Ornithology explored patterns across the genomes of these birds and find them to be incredibly similar at the molecular level. In spite of the strong similarity, they still have the ability to distinguish the western Red-shafted Flickers from the eastern Yellow-shafted Flickers for the first time through the use of new genomic methods. Genomic technology is advancing at such a rapid rate that genetic sequence differences that were undetectable in the 1980s using (then) cutting-edge methods are now readily apparent using next-generation sequencing techniques.

“Flickers have intrigued ornithologists and naturalists at least as far back as Audubon, but only recently has it become possible to understand these birds genomically,” says lead author Stepfanie Aguillon. “I was unsure what we would find, given how much trouble previous researchers have had with these birds. I was surprised—and excited—by how similar we found them to be since we now had thousands of markers across the genome. I think this paper underlies a theme that has become more and more apparent over the last few years—even when two birds look very different, they may not be very different genetically.”

“The hybrid zone between the yellow- and red-shafted flickers is particularly striking, but despite very apparent morphological and ecological differences, genetic studies beginning in the late 1980s found few differences between these two ‘subspecies,’” adds flicker expert William S. Moore, a Wayne State University professor who was not involved with this research. “Hybrid zones are often described as “natural laboratories” for studies on speciation. Despite the low level of genetic divergence across the flicker hybrid zone, it is certain that selection is operating on genes involved in plumage divergence and ecological adaptation. Aguillon’s study will be a foundation stone for studies that identify the adapted genes and will bring us to a new understanding of the processes of speciation.”

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A flicker of hope: Genomic data distinguish Northern Flicker taxa despite low levels of divergence is available at http://www.bioone.org/doi/full/10.1642/AUK-18-7.1
Researcher contact: Stepfanie M. Aguillon, sma256@cornell.edu

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.

Whiskered Auklets Lack Wanderlust, Are Homebodies Instead

Wed, 05/30/2018 - 09:17

Whiskered Auklet (Photo Credit: Ian Jones)

A new study from The Auk: Ornithological Advances presents some of the best evidence that Whiskered Auklets are an outlier in the auklet family by not migrating and instead staying close to “home” (their breeding colonies) year-round. Most migratory birds lead two opposite lifestyles in the same year. During the breeding season a bird’s location is constrained and their habits are repetitive given a nest full of chicks that require food, warmth, and protection. For some birds it is the only time they congregate or otherwise come together. Comparatively, during the non-breeding season their only true task is to survive. Whether migratory or residential, as long as the bird makes it back to the breeding grounds to reproduce, they can go almost wherever they want. Whiskered Auklets are consistent through the year though and don’t wander far at all.

Carley Schacter and Ian Jones of Memorial University of Newfoundland used light-based archival geolocation tags on Whiskered Auklets in Buldir Island, Aleutian Islands, Alaska, to determine the locations of their full annual life cycle. The data they collected corroborated what researchers have long suspected. This species is unique in the auklet family for not migrating at all. Most seabirds roost on the water at night, but Whiskered Auklets stay in the vicinity of the breeding colony year-round and consistently return to roost at night on land. Such behavior may not only be unique to auklets, but to the entire seabirds group. How could this unusual adaptation have come about? Whiskered Auklets capitalize on the foraging habitat close to their breeding colony which reduces metabolic costs. Given the influence of tradeoffs on animal behavior and life history strategies, this foraging area could be a large contributor to their residential behavior.

But there are risks to this strategy as well. Lead author Carley Schacter notes, “While this non-migratory behavior is very interesting to us on a theoretical level, there are also important implications for the conservation and management of this most vulnerable of auklet species. Year-round residence near the breeding site (an area of high fishing and shipping traffic) makes Aleutian-breeding Whiskered Auklets even more exposed than previously thought to human threats such as oil/fuel spills and light attraction leading to fatal collisions with vessels. Their nocturnal roosting behavior also makes them especially vulnerable to introduced mammalian predators such as rats and foxes.”

“The authors found evidence for an almost unique adaptation of a seabird in a remote, difficult-to-work-in, and isolated environment,” adds Jeff Williams, Assistant Refuge Manager at the Alaska Maritime National Wildlife Refuge, who was not involved with this research. “We now know that Whiskered Auklets are particularly sensitive to human-caused disturbances (oil spills, light attraction, invasive species introductions etc.) and can incorporate this information into management planning.”

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Confirmed year-round residence and land roosting of Whiskered Auklets (Aethia pygmaea) at Buldir Island, Alaska is available at http://www.bioone.org/doi/full/10.1642/AUK-17-235.1
Researcher contact: Carley R. Schacter, crs634@mun.ca

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 One Invasive Insect Can Change a Forest Bird Community

Thu, 05/24/2018 - 11:58

Acadian Flycatcher in Hemlock forest (Photo Credit: D Williams)

Eastern hemlock forests have been declining due to a non-native insect pest, the hemlock woolly adelgid. A new study from The Condor: Ornithological Applications presents some of the best long-term data showing how the decline of a single tree species (eastern hemlock) leads to the disappearance of birds specialized to those trees. The data also indicate birds associated with non-hemlock habitat features (deciduous forest, woodland edge, and shrubs) are spreading into former hemlock forests. A single insect species has led to a less diverse bird community across this landscape.

Pennsylvania State University’s Matthew Toenies and colleagues analyzed a long-term response to the decline of eastern hemlocks using vegetation and bird abundance surveys. The researchers took advantage of surveys they had conducted in 2000 before adelgids had caused hemlock decline and compared those data to new data from the same forests in 2015-16, after decline. They then analyzed how both individual bird species and groups of species responded to this habitat change.

The data showed that as hemlocks became less abundant in the forest, the bird species most associated with these trees also disappeared. As the hemlock-specific birds left, birds that are normally found in more general hardwood forests replaced them. Thus, biodiversity was reduced with the decline of hemlocks as well and the composition of the landscape became more similar over a larger area.

“Invasive species, climate change, and land-use change are all similar in that they make our world a less diverse place, and this study helps greatly in understanding how the loss of the eastern hemlock plays its own role in the degradation of biodiversity,” adds University of Connecticut Professor Morgan Tingley, a community ecologist who was not involved in this research.

Lead author Matthew Toenies says, “To sum up, to people who are saddened by the loss of hemlocks and the birds that rely on them, I would say one thing: We cannot turn back the clock–we cannot un-introduce the hemlock woolly adelgid; but we absolutely possess the power to prevent this story from repeating itself.”

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Shifts in vegetation and avian community structure following the decline of a foundational forest species, the eastern hemlock, is available at http://www.bioone.org/doi/full/10.1650/CONDOR-17-204.1.
Research contact: Matthew Toenies, mkt5213@psu.edu

 

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. In 2016, The Condor had the number one impact factor among 24 ornithology journals.

 

Birds play the waiting game in tough environmental conditions

Wed, 05/23/2018 - 12:37

Banded Willow Flycatcher in the hand (Photo Credit: Tad Theimer)

Every animal’s ultimate goal in life is to generate offspring to pass on its genetic material to the next generation. But sometimes, resources are scarce and the task of reproduction is too difficult or risky. If resources are limited and tough to find, reproductive efforts may fail anyway. In these situations, it may be in an animal’s best interests to not defend a territory or to breed at all, but rather to focus its efforts on surviving to the next breeding season. Biologists refer to individuals without a territory during the breeding season as ‘floaters’. A new study from The Auk: Ornithological Advances presents some of the best evidence on how changes in environmental conditions, specifically droughts, impact the social and reproductive behavior of birds.

Tad Theimer of Northern Arizona University and colleagues monitored a population of Willow Flycatchers over a five-year period. Each individual in this population was marked with uniquely colored leg bands and its behavior recorded throughout the breeding season. Some of these birds defended territories that contained their nests, while other birds – the floaters – moved around the population declining territory and nest. A severe drought that occurred during the study allowed the researchers to examine how these birds respond to changes in the environment. They found there were one and a half times more floaters during the drought than during years with average rainfall, and that these floaters were more likely to survive than individuals that tried to nest. When the researchers compared how many chicks a bird had with their floater status the previous year, they found that territorial birds had more chicks than floaters – with one exception. In the year immediately after the drought, former floaters produced more chicks.

There is a potential twist in the story though because the researchers did not check the DNA of the chicks throughout the study. Birds are notorious for extra-pair copulations (or breeding with another individual that is not your mate), and it’s probable floaters engage in this behavior regularly. Through this behavior, they get the benefit of passing on their genes without the cost of raising the chick.

As lead author Theimer puts it, “In normal years all birds try to breed, and those that don’t breed lose out in long-term reproductive success, but in extreme drought years, not breeding is actually the better strategy”. But this strategy of patience assumes that next year will be better than this year. As climate change increases the frequency of these extreme environmental conditions, this assumption becomes less certain.

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Extreme drought alters frequency and reproductive success of floaters in Willow Flycatchers is available May 23, 2018, at http://www.bioone.org/doi/full/10.1642/AUK-17-206.1
Researcher contact: Tad Theimer, Tad.Theimer@nau.edu

 

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.

 

Darwin’s Finches – Where Did They Actually Come From?

Tue, 05/15/2018 - 12:20

Española cactus finch (geospiza conirostris) Photo credit: S Taylor

In 1835, Charles Darwin visited the Galapagos Islands and discovered a group of birds that would shape his groundbreaking theory of natural selection. Darwin’s Finches are now well-known as a textbook example of animal evolution. But just where did a species synonymous with the discovery of evolution come from? A new study from The Auk: Ornithological Advances presents some of the best models to date on where these birds actually originated.

San Diego State University’s Erik Funk and Kevin Burns set out to determine the ancestral biogeography – how a species’ distribution varies over space and time – of Coerebinae. Coerebinae is a subfamily of birds called tanagers. This group includes the famous Darwin’s Finches and their fourteen closest relatives. Using state-of-the-art statistical software, Funk and Burns modeled two competing hypotheses. Both hypothesis models contained the same geographic area of the Galapagos, South America, and the Caribbean, but one model divided this area into more subregions than the other. The subregions were based on areas that shared similar plants and animals, such as the the Amazon or the Andes. When eight subregions were included in the model, the results indicated that the Caribbean, not the closer South American mainland, was more likely to be the origin of this bird group. However, the opposing model contains only five regions and indicates that the South American mainland is as likely as the Caribbean to be the home to Darwin’s Finches’ ancestors. The authors conclude that the current data suggest both potential origin sites are equally likely. Funk says, “the results…were a bit surprising, because they suggested a dispersal pattern that was not necessarily the most ‘straightforward’ explanation for how these birds arrived in the Galápagos. I think one of the big take-away messages here is the possibility that biogeographic events, like dispersal, may not necessarily happen like logic tells us they should. Darwin’s finches are such a highly studied group, and it is often taken for granted they arrived from mainland South America, but hopefully our results show readers that there is no more support for this hypothesis than there is for a Caribbean origin.”

Funk and Burns suggested the successful colonization of the Galapagos Islands was a result of two traits. First, the finches’ ancestors were more likely to wander than other species and consequently encountered islands more often. Second, these ancestors had a large amount of genetic variation in bill size and shape. This diversity in bill morphology allowed them to establish themselves and exploit their newfound niche. Better understanding the biogeography of Darwin’s Finches allows scientists to learn how animals move, and how this affects their subsequent evolution and ability to adapt to new or changing environments.

“In 2018, we still have fundamental things to learn about one of the most studied and celebrated groups of birds, Darwin’s Finches. Perhaps we should be calling them Darwin’s Tanagers because it is Burns’ tree of life for these birds, nesting them firmly in Tanagers, that is enabling new insights into the evolution, morphology, and origins of this remarkable group of birds. Funk and Burns use new biogeographic techniques in conjunction with recent phylogenies to explore the origins of Darwin’s Finches,” adds Shannon Hackett, Associate Curator in the Department of Zoology, and Head of the Field Museum’s Bird Division at the Field Museum, who is an avian diversity and phylogeny expert who was not involved in the research.

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Biogeographic origins of Darwin’s finches (Thraupidae: Coerebinae) will be available May 9, 2018, at http://www.americanornithologypubs.org/doi/full/10.1642/AUK-17-215.1

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.

Wintering Warblers Choose Agriculture Over Forest

Tue, 05/08/2018 - 13:15

Yellow Warbler Photo credit: S Valdez

Effective conservation for long-distance migrants requires knowing what’s going on with them year-round—not just when they’re in North America during the breeding season. A new study from The Condor: Ornithological Applications uncovers Yellow Warblers’ surprising habitat preferences in their winter home in Mexico and raises questions about what their use of agricultural habitat could mean for their future.

Large areas of natural forest in the Mexican lowlands have been converted to agriculture, and without enough habitat to go around, researchers speculate that the biggest, oldest birds might claim the choicest spots. To find out, Simon Fraser University’s Simón Valdez-Juárez and his colleagues studied Yellow Warblers wintering in western Mexico, counting how many birds were using each of three different types of habitat—riparian gallery forest, scrub mangrove forest, and agricultural land—as well as capturing birds to determine their age, sex, size, and likely point of origin. To their surprise, they found the highest density of warblers in agricultural habitat rather than either type of natural forest. There was also little evidence that a bird’s body size, sex, or age influenced where it ended up, although females’ habitat use differed depending on where they had spent the breeding season.

Irrigated agriculture may be attractive to Yellow Warblers as an alternative to the naturally dry forest habitat, which becomes even drier as winter goes on, or the limited availability of natural land cover may force most birds to occupy agricultural areas. Either way, this preference for agriculture could lead to problems if stressors such as pesticide use reduce the birds’ survival. “The implications for migratory bird populations depend on whether the condition and survival of birds wintering in agriculture is lower than that of birds wintering in natural habitats or not,” says Valdez-Juárez. “If it is lower, it might cause localized declines, as females from the contiguous U.S. and western Alaska were more likely to use agricultural habitats and lower female survival has been implicated in the population declines of other warblers.”

“With increasing agricultural intensification across the ranges of many long-distance migratory songbirds, it is critical to determine if they are using these new habitats. This new study shows that yellow warblers overwintering in western Mexico not only use agriculturally dominated habitats but are more common there than nearby sites with more natural landcover,” adds University of Manitoba Assistant Professor Kevin Fraser, an avian behavior and conservation expert who was not involved in this research. “They also report that more southern breeding females are more likely to use agricultural habitats than more northern breeding females, suggesting any impacts of overwintering habitat use may differ by breeding latitude. These results are important, as they highlight the need to investigate whether regions undergoing agricultural intensification are providing viable habitat for overwintering migrants, and how their use may carry-over to impact survival or fecundity in subsequent seasons.”

Use of natural and anthropogenic land cover by wintering Yellow Warblers: The influence of sex and breeding origin will be available May 2, 2018, at http://www.bioone.org/doi/full/10.1650/CONDOR-17-180.1 (issue URL http://www.bioone.org/toc/cond/120/2).

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. In 2016, The Condor had the number one impact factor among 24 ornithology journals.

Where do birds molt their feathers? New research indicates molting grounds are discrete from breeding and wintering sites.

Mon, 05/07/2018 - 09:09

Nashville Warbler, one of 140 species whose post-breeding movements to molting areas were examined in a new study by The Institute for Bird Populations. Results indicate that Nashville Warblers in western North America disperse upslope from breeding areas to molt, whereas in the East, they move downslope and south. Many such east-west differences within species were found, reflecting differing climate and insect availability across North America. This photo was taken in August, when Nashvilles are on their molting grounds. (Photo by Frank D. Lospalluto via Flickr Creative Commons).

A new study by The Institute for Bird Populations finds that many North American birds do not molt on their breeding territories, as previously thought, but disperse or migrate in late summer to discrete molting locations before continuing their migration to wintering areas. The locations and habitats at these molting sites — and their conservation status — remain largely unknown.

Effective conservation of migratory birds depends on the protection of habitats used during all phases of their life cycle. New research by The Institute for Bird Populations, a non-profit bird conservation organization, has shed light on a key phase of the annual cycle: where birds go to molt after they breed. The study was published May 2, 2018 in the journal The Auk: Ornithological Advances.

Molt is an energetically taxing process during which birds shed worn or broken feathers and grow new ones. During this time, a bird’s flight ability is reduced, so they become harder to find than at other times of year. “Molt has been under-studied by ornithologists. Birds become very retiring at this time, as if on vacation, to recover from the breeding season,” said Peter Pyle, lead author on the study. Despite its importance to a bird’s survival, the subject has received a lot less attention than other factors such as breeding, migration, and wintering habitats. “We still have no clue where most North American landbirds undertake their post-breeding (prebasic) molt, and we need more information on the particular habitats or foods that are most important, and the conservation status of these areas.”

The new study relied on 17 years of records from The Institute for Bird Populations’ Monitoring Avian Productivity and Survivorship (MAPS) Program, a continent-wide bird banding effort assisted by thousands of citizen scientists and professional biologists. Data from more than 760,000 capture records of 140 species of landbirds collected at 936 MAPS bird-banding stations across North America were used to generate the results. The authors leveraged this extensive data set to estimate what proportion of birds known to breed at a station were also captured molting there, and vice versa. Dashed lines indicate delineation of western and eastern North America.

Although some bird species are known to undergo “molt-migrations” — movement to a molting location that is neither where they nested nor where they will winter — to take advantage of wetter conditions or more abundant food in areas such as the Sierra Nevada mountains in California or the late summer monsoonal rain area in the desert Southwest, most species have been assumed to molt on or near their breeding territories. This turns out not to be the case.

The study demonstrated some surprising findings, including widespread evidence of molt-migration for many species previously thought to molt only on their breeding grounds. The researchers analyzed spatial differences between breeding and molting locations, and found evidence that, across North America, birds shifted in nearly every compass direction, and with some going higher in elevation and some lower to find suitable molting areas. “In some cases this may be hundreds of kilometers away, in others it may be down the block,” Pyle noted.

Most of the 140 species examined (indicated by 4 letter codes abbreviating their common names) showed movements from breeding to molting areas. Species lower/further left on each graph show a lower probability of being recaptured during molt at a site where it bred. In the graph, species names in orange were known to molt away from breeding grounds, those in blue were thought to molt on breeding territories, and those in black are residents, presumed to molt on or near breeding territories. The new study largely validates these results for species marked in orange and black, but many species previously presumed to molt on breeding grounds (those in blue) appear to undergo molt migrations.

Although western North American species and populations have previously been reported to undergo more molt-migration than eastern species, this study found similar evidence of molt-movement between the two regions, although many species in the west migrate longer distances.

Two examples of molt migration movements by North American birds. Bluer areas represent higher probability of a bird breeding relative to molting at that site and redder areas represent higher probability of molting relative to breeding. As with Nashville Warbler (see above), Orange-crowned Warblers in the West moved significantly further south and higher in elevation, largely into the Sierra Nevada mountains of California, likely to take advantage of cooler and moister habitats at these locations in late summer. Within the MAPS area, Swainson’s Thrushes in the East appeared to shift west and south, largely into the Mississippi Valley, but did not appear to shift elevations.

These findings have significant implications for conserving birds. Although molting areas appear to be crucial for completing a species’ annual life cycle, more study is needed to determine if such areas are receiving the conservation attention or protection they need. The new research also indicates that individuals within a species make various molt-movement choices, even on an annual basis, in response to breeding season success or environmental and food conditions each year. “Rather than characterizing molt as occurring on discrete breeding or wintering grounds, it can perhaps best be thought of as a process occurring along a continuum, with most some species, populations, or individuals showing some level of movement from breeding territories to molt,” said Jim Saracco, another author on the study. “Our findings highlight the need for better understanding of molt-movement patterns and habitat needs during molt to better inform full life-cycle conservation strategies.”

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Evidence of widespread movements from breeding to molting grounds by North American landbirds is available at http://www.bioone.org/doi/full/10.1642/AUK-17-201.1 For more information about this study, contact Peter Pyle (ppyle@birdpop.org).

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.

Is the Rufous Hummingbird a Mexican monsoonal molt migrant?

Fri, 05/04/2018 - 11:58

Rufous Hummingbird, Photo credit: T Hopwood

Many species of North American hummingbirds are highly migratory, with some traveling over 2,000 km. These migratory birds risk more feather wear due increased solar exposure on an annual basis compared to non-migratory species. Hummingbirds, like all birds, need their feathers to be in good condition to survive and therefore have to undergo molt.

All North American migratory hummingbirds undergo complete molts on wintering grounds in Mexico before they migrate north. In first-year birds, this complete molt has been referred to as the performative molt and in all subsequent years, it is called the definitive prebasic molt. First-year males were also known to replace some throat feathers during the fall, replaced again during the complete overwinter molt.

However, a recent study by Dittmann and Cardiff suggested that molting in migratory hummingbirds may be more complex than simply the annual molt (2009, Birding 41: 32–35). They examined molt of Ruby-throated Hummingbirds during their fall migration from June to September on the Gulf Coast of Louisiana and found evidence of molting at this time in both adults and young. They called this molt an inserted molt, separate from the overwinter complete molt.

Curious whether inserted molts might occur in other migratory hummingbird species, we examined molt in the Rufous Hummingbird, a Mexican species that migrates to the northern United States and Canada to breed. We examined 346 specimens of Rufous Hummingbirds from three different specimen collections in California. We looked at each specimen for signs of molt in four feather regions: the crown, the back, the throat (including the gorget in adult males), and the underparts. We considered a bird as showing evidence of molt if we found any replaced feathers contrasting with worn feathers, indicating two generations of feathers in a single region, or if we found pin feathers present in any of the regions.

As expected, the majority of the specimens collected in the winter from southern Mexico showed signs of the complete molt that was known to take place on the wintering grounds. However, we also found signs of molting in both young birds and adults during southbound migration in the fall. These inserted molts occurred in all four feather regions but were more limited in extent than those of Ruby-throated Hummingbirds. Many (but not all) molting specimens were collected in the Mexican monsoonal region of northwestern Mexico. The Sierra Madre Occidental, a mountain range that lies within the monsoonal region attracts Rufous Hummingbirds because of the high flower abundance that occurs there, and we infer that the hummingbirds take advantage of this food resource to molt in this area, as do many western North American species of passerines.

Surprisingly, we found that the inserted throat feather molt in Rufous Hummingbirds varied greatly among ages and sexes. Adult males showed no evidence that their iridescent throat feathers were replaced in fall, whereas some adult females and all young birds of both sexes replaced at least some throat feathers during the inserted molt. New iridescent throat feathers might give young birds an advantage when defending territories by showing dominance. While it is still unclear why the highly migratory Ruby-throated and Rufous Hummingbirds undergo inserted fall molts in other body regions, one reason could be that their feathers become more worn compared to non-migratory hummingbirds.

We compared molts of Rufous Hummingbirds to the molts of basal Apodiform taxa, including Vaux’s Swift and Rivoli’s Hummingbird. We propose a terminology that would consider the inserted molts as the definitive prealternate molt in adults and the preformative molt in young birds. Therefore, we propose that Rufous Hummingbirds undergo a prealternate and preformative molt migration to the Mexican monsoonal region.

Our work on Rufous Hummingbirds is part of The Institute for Bird Populations’ Avian Molt Research Program, aimed at understanding molt strategies of all species of birds, standardizing molt and plumage terminologies worldwide, and applying findings to age-related demographic studies, habitat requirements for molt, and, ultimately, the conservation of birds.

~Post written by authors: Desmond Sieburth and Peter Pyle

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Evidence for a prealternate molt-migration in the Rufous Hummingbird and its implications for the evolution of molts in Apodiformes is available, at http://www.bioone.org/doi/full/10.1642/AUK-17-231.1 (issue URL http://www.bioone.org/toc/tauk/135/3).

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.

Rethinking the Umbrella Species Concept

Wed, 05/02/2018 - 16:54

Brewer’s Sparrow’s nest. Photo credit: J Carlisle

According to the “umbrella species” concept, preserving and managing habitat for a single high-profile species also benefits a whole suite of other species that share its habitat—but how well does this really work? Not all species that share the same general habitat necessarily have the same specific needs, and a new study from The Condor: Ornithological Applications finds that habitat management to benefit Greater-Sage Grouse in Wyoming can actually harm some of its songbird neighbors.

Shrub mowing is sometimes done to benefit sage-grouse during their chick-rearing season, when they favor habitat with fewer shrubs and more grass and forbs. The University of Wyoming’s Jason Carlisle (now at Western EcoSystems Technology) and his colleagues collected data on the abundance and nesting success of three songbird species before and after shrub mowing in central Wyoming, as well as at un-mowed sites for comparison. Two of the species, Brewer’s Sparrows and Sage Thrashers, are “sagebrush obligates” that rely heavily on shrub habitat. The researchers found no Brewer’s Sparrow or Sage Thrasher nests in mowed patches, where it may be decades until shrubs have regrown enough to be used for nesting, and the mowing treatment also reduced the overall abundance of Sage Thrashers by around 50%. Vesper Sparrows, on the other hand, are more flexible in their habitat use and were actually more abundant in patches where mowing was most extensive.

“The umbrella species concept is an appealing shortcut,” says Carlisle. “However, when conservation practitioners go beyond protecting the umbrella species’ habitat and start manipulating habitat conditions to meet the needs of the umbrella species, they risk harm to other species that also rely on those areas.” The mowed area in the study was only about five square kilometers, and cost and logistics make in unlikely that this treatment will be implemented on a large scale, so the negative effects of these habitat manipulations are likely more than offset by the positive effects of broader-scale sage-grouse conservation efforts. Still, Carlisle and his colleagues suggest that more monitoring is needed in general of how non-target species fare under umbrella-species management.

“It is clear that the observed effects on ‘background’ species are not consistent across the range of potential beneficiaries, and that the assumed benefits do not accrue to many,” adds Russel Norvell, an Avian Conservation Program Coordinator at the Utah Division of Wildlife Resources, who was not involved with this research. “It is likely these effects will persist, given the relatively slow growth rates in this arid system. While the conservation of Greater Sage-Grouse habitats across its range is likely to encompass much good, local habitat manipulations driven by unexamined assumptions or uninformed by landscape context have much to prove.”

Nontarget effects on songbirds from habitat manipulation for Greater Sage-Grouse: Implications for the umbrella species concept is available at http://www.bioone.org/doi/full/10.1650/CONDOR-17-200.1 (issue URL http://www.bioone.org/toc/cond/120/2).

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. In 2016, The Condor had the number one impact factor among 24 ornithology journals.

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

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