New Evidence for California Condors’ Genetic Bottleneck

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California Condors have lost 80% of their genetic diversity. Photo credit: J. D’Elia

The existing genetic diversity of California Condors, all of which are descended from just 14 individuals, is strikingly low. But were condors more genetically diverse before their 20th century population crash, or were they already, as one paleontologist put it in the 1940s, a Pleistocene relict with “one wing in the grave”? The researchers behind a new study in The Condor: Ornithological Applications analyzed samples from condor museum specimens dating back to the 1820s and found that the historical population was surprisingly diverse, but that a substantial amount of that diversity was lost in the last two centuries. This finding supports the hypothesis that condors were fairly widespread and abundant prior to increases in human-caused mortality, which likely drove their numbers down quickly in the 1800s and early 1900s.

Analyzing the museum specimens’ mitochondrial DNA, Jesse D’Elia of the U.S. Fish and Wildlife Service and his colleagues showed that more than 80% of the unique haplotypes present in the birds of the past have disappeared from the gene pool of condors alive today. The low amount of genetic diversity in the current population, which is descended from only 14 genetic founders from the captive flock, was already well known, but this was the first study to show that there was substantial genetic diversity in the historical population.

D’Elia and his colleagues used tissue samples from 93 California Condor specimens collected between 1825 and 1984 in locations ranging from Mexico to Washington state. “The value of museum collections for answering important questions when considering population translocations and species’ reintroductions cannot be overstated,” says D’Elia. “They provide a direct window into a population’s history and as new genetic and genomic tools continue to be developed the value of these specimens only increases.”

The genetic bottleneck resulted in inbreeding and decreased fitness, and condors will continue to require intensive management for some time to recover. But there is a possible upside for condor conservation in the results of this study—D’Elia and his colleagues did not find any evidence that the now-vanished Pacific Northwest population was genetically isolated from the condors in California. If Northwest condors weren’t on a separate evolutionary track, there’s no reason not to release today’s captive-bred condors into those unoccupied areas of their historical range.

“These results document a significant decline in mitochondrial DNA diversity over the past century, which also suggests a corresponding reduction in nuclear DNA diversity,” according to Jeff Johnson of the University of North Texas, an expert on incorporating genetic information into conservation efforts. “Therefore, the careful attention made to maintain founder lineages and prevent inbreeding is critical for improving the likelihood of producing an eventual self-sustainable wild population. Those involved in the California Condor recovery efforts are leading experts in captive propagation and release, and the methods developed and used, particularly those benefiting from whole nuclear genome approaches, acknowledge the importance of maintaining existing genomic diversity both at the individual and population level.  These methods will also benefit other endangered species captive breeding programs that possess similar demographic histories.”

Ancient DNA reveals substantial genetic diversity in the California Condor (Gymnogyps californianus) prior to a population bottleneck is available at http://americanornithologypubs.org/doi/full/10.1650/CONDOR-16-35.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology published by the American Ornithological Society. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society.

Choosy Sage-Grouse Select Nest Sites to Maximize Their Success

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Nesting female sage-grouse. Photo credit: S. Beh

Do sage-grouse know what’s good for them when choosing where to nest? That’s the question at the heart of a new study in The Condor: Ornithological Applications, in which researchers examined the habitat preferences of these vulnerable grassland birds. They found that females look for vegetation characteristics that will boost their reproductive success when selecting nest sites, giving land managers new hints about what types of habitat are most in need of protection.

Theory says that animals should select habitat that maximizes their fitness, but reality doesn’t always live up to this—climate variability, habitat degradation, and predator–prey interactions can all push individuals into using “maladaptive” habitat that hurts their chances to survive and reproduce. Dan Gibson of the University of Nevada Reno and his colleagues examined how Greater Sage-Grouse in Nevada selected their nest sites and found that despite population declines, females were choosing spots with characteristics associated with reproductive success, such as greater shrub cover and forb diversity. The greatest effect was on the survival of chicks after they fledged, suggesting females were selecting nesting habitat based on its promise for getting their chicks through that particular life stage.

Gibson and his colleagues monitored more than 300 female sage-grouse between 2004 and 2012 in Eureka County, Nevada. Capturing them and equipping them with radio transmitters, they tracked the birds to their nests and monitored them weekly to follow their progress through the breeding season. By collecting data on the vegetation surrounding each nest site, they were able to determine what types of habitat were most associated with positive outcomes.

The authors of this study propose that areas with active sage-grouse breeding grounds, or “leks,” that are located in habitat correlated with high reproductive success should be the highest conservation priority. “In a conservation context, our approach linking habitat selection with demographic success allows managers to move beyond designating areas as habitat based solely on observations of individuals,” says Gibson. “This should provide increased resolution for ranking habitat in terms of both its importance to an individual species and its management priority.”

“Gibson et al. confirm the importance of fine-scale habitat characteristics for sage-grouse nest and chick survival,” according to Dave Dahlgren, a sage-grouse expert from Utah State University who was not involved with the study. “This paper contributes to sage-grouse conservation efforts by demonstrating the scale and habitat diversity (e.g., shrub species diversity) selected for and which factors ultimately contributed to fitness within the population.”

Nesting habitat selection influences nest and early offspring survival in Greater Sage-Grouse is available at http://www.americanornithologypubs.org/doi/abs/10.1650/CONDOR-16-62.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society.

Migrating Birds Speed Up in Spring

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Migratory birds like Baltimore Orioles travel faster in spring than in fall. Photo credit: K. Horton

It turns out being the early bird really does have its advantages. A new study in The Auk: Ornithological Advances shows that migrating birds fly faster and put more effort into staying on course in spring than in fall, racing to arrive to their breeding grounds as soon as possible to get an edge in raising the next generation.

Migrating birds travel faster in spring than in fall because arriving late to their breeding grounds can affect their reproductive success. Past studies have shown that migrants take shorter breaks in spring, but it’s harder to tell whether they also move faster in the air. When they used high-tech weather surveillance radars operated by NOAA and the Department of Defense on migrating birds, Kyle Horton of the University of Oklahoma and his colleagues found that birds did indeed fly faster in spring and compensated more for crosswinds that could blow them off course.

“Many migration studies look at a few individuals, maybe on the scale of hundreds, but with radar, we’re now documenting the behaviors of millions of individuals on a given night. That’s a lot of data, and when you do see flight behavior results that are regionally or seasonally different, it’s quite compelling,” says Horton. He hopes birds’ ability to adjust their migratory behavior for different conditions will buffer them against the effects climate change, which may cause large-scale shifts in wind intensity.

This study made use of recent upgrades to government radar stations. “In 2013 an additional plane of polarization was added to the radars, giving us another dimension to look at migratory birds, among other things,” explains Horton. “This allowed us to measure the orientation of birds directly for the first time.”

“Horton et al. have tapped the great potential of large-scale surveillance radars to advance our understanding of migration ecology,” adds the University of Delaware’s Jeff Buler, a radar ecology expert who was not involved in the study. “Their novel analysis reveals macroscale patterns in the aggregate behaviors of migrating birds that support existing literature on flight strategies of migrants. In addition, their analysis makes new discoveries about greater overall wind compensation during spring and new hypotheses about the processes underlying these patterns.”

Seasonal differences in landbird migration strategies is available at http://americanornithologypubs.org/doi/abs/10.1642/AUK-16-105.1.

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. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

Overcrowding Forces Pheasants to Cooperate in Hawaii

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A Kalij Pheasant in Hawaii. Photo credit: L. Zeng

“Survival of the fittest” usually means that animals put their own needs first, but occasionally it pays to work together. A new study in The Auk: Ornithological Advances describes an unusual example of cooperative breeding in an introduced pheasant population in Hawaii, where young males help care for chicks and defend against intruders rather than striking out on their own.

Cooperative breeding, where members of a social group provide care to young that are not their own offspring, is rare in “precocial” bird species like pheasants—those where chicks are already well-developed when they hatch and don’t require intense parental effort. However, Lijin Zeng of the University of California–Riverside and her colleagues have discovered that cooperative breeding is the norm among Kalij Pheasants in Hawaii’s Volcanoes National Park. While females incubate their eggs alone, all group members, including up to six males as well as the breeding female, feed the chicks after they hatch and defend the group against intruders. Dominant males father the most chicks, but almost a third are fathered by subordinate males within the same group or males from other groups.

This is only the third time cooperative breeding has been observed in the pheasant family, and Kalij Pheasants, introduced in Hawaii in the 1960s, are not known to breed cooperatively in their native range in Asia. Possibly due to a lack of predation and disease, their population density in Volcanoes National Park has grown very high, and overcrowding may prevent young males from being able to establish their own territories. Instead, their best hope to pass on their genes is to stay with the group and wait to move up in the dominance hierarchy, fathering a few chicks in the meantime.

Zeng and her colleagues spent years trapping individuals to color band them for easy identification and to take blood samples. They located nests by tracking females with radio-transmitters and closely observed groups to determine their composition and hierarchies. “Observing the pheasants’ behavior and social relationships was very interesting and fun,” says Zeng. “I spent so much time getting to know my birds and their siblings, spouses, and children, and I suspect that some of them learned to identify me as well!”

“Cooperative breeding is thought to be rare in pheasants, but a few recent papers have challenged this view. In their study of Kalij Pheasants in an introduced population in Hawaii, Zeng et al. reveal that the social system of Kalij Pheasants is far more complex than previously thought,” according to Princeton University’s Christina Riehl, an expert on cooperative breeding. “The detail and completeness of this research is truly impressive, illuminating not just individual reproductive strategies, but also how population-level ecological constraints shape the evolution of these strategies.”

Social behavior and cooperative breeding in a precocial species: The Kalij Pheasant (Lophura leucomelanos) in Hawai’i is available at http://americanornithologypubs.org/doi/abs/10.1642/AUK-15-227.1.

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. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

The Pros & Cons of Supplementary Materials in Scientific Publishing

The ascendance of the Internet has changed academic publishing in ways that scientists are still adjusting to. A new commentary in The Auk: Ornithological Advances examines the costs and benefits of supplementary materials, which are online-only additions to scientific papers that often contain datasets, audio and visual files, and other hard-to-classify resources.

Dave Shutler and Ashley Murray of Nova Scotia’s Acadia University analyzed trends in the use of supplementary materials since 2000 in 13 journals widely read by ornithologists. Ten showed significant increases in the use of supplementary materials over time, in some cases with a corresponding decrease in appendices, which (unlike supplementary materials) are included in print versions of journals.

Papers with supplementary materials add complexity to every step of the publication process. They place additional demands on authors, who must decide what’s relevant enough to include and spend time preparing and submitting the materials; reviewers, who already volunteer their time to ensure the quality of published studies and who in some cases refuse to review supplementary materials; and journal production teams, who must spend time copyediting and formatting the materials. Navigating journal websites to find supplementary materials can be time-consuming and frustrating for readers, especially those who prefer to work with print copies of studies.

However, supplementary materials can add value as well. They give researchers almost unlimited capacity to publish information relevant to a study, reduce printing costs, and make it possible to publish material that can’t be included in print, such as sound and video files. “My hope is that, among other things, we will all take a step back and evaluate what belongs as supplementary materials and how much we want to invest in ensuring that supplementary materials are legitimate contributors to advancing science,” says Shutler.

“No one writes about the role of supplementary materials,” adds Auk Editor-in-Chief Mark Hauber. “The phenomenon just happened and now we all have to live with it. It’s surprising to think that in an era of online publishing, we should need unreviewed sections of papers to be available to understand the reviewed components of the paper.”

Trends, costs, benefits, challenges, and prognoses for supplementary materials is available at http://www.aoucospubs.org/doi/full/10.1642/AUK-16-92.1.

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. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

Which Snowy Owls Thrive in Saskatchewan’s Winters

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Researcher Karen Wiebe holds a Snowy Owl. Photo credit: K. Jacobsen

Snowy Owls capture the imagination, but ornithologists know surprisingly little about how these birds of the far north fare during the harsh winters they endure. The researchers behind a new study in The Auk: Ornithological Advances trapped and tracked Snowy Owls wintering in Canada and found that while age and sex affect the birds’ condition, most do fairly well, showing few signs of starvation and some even putting on weight over the winter months.

Female Snowy Owls are bigger than males, and Alexander Chang and Karen Wiebe of the University of Saskatchewan expected that their dominant behavior would give females access to greater food resources during the challenging winter season. Their results bore this out—females tended to be in better condition than males, and adults, with their greater hunting experience, tended to be in better condition than juveniles.

It’s widely believed that Snowy Owls that winter south of the Arctic tend to be struggling, starving birds that only move south because they can’t find enough to eat at home, but few of the adults captured in the wild showed signs of starvation. Surprisingly, many of the adult birds in the study actually increased their fat stores slightly over the course of the winter. Well-insulated against the cold and not distracted by the demands of reproduction, Snowy Owls may use winter as a time to recharge and build up their reserves before returning to their breeding grounds.

Much of the data for the study was collected by two retired farmers, Marten Stoffel and Dan Zazelenchuk, who discovered a love of owls and pursued raptor banding as a hobby. “They had no intention of analyzing data, but spent numerous hours in the field in grueling sub-zero weather honing their trapping techniques and drinking liters of coffee while waiting—sometimes hours—for an owl to come to a trap,” says Wiebe.

“This study by Chang and Wiebe nicely shows that most snowy owls wintering in the Prairies are in good body condition and, contrary to a commonly held belief, are not starving despite the harsh environmental conditions that prevail in winter,” according to Gilles Gauthier of Quebec’s Université Laval, an expert on Arctic wildlife. “This study clearly documents differences in body condition between age classes and sexes. The results are very robust, as they are based on large sample sizes spanning a period of almost 20 years.”

Body condition in Snowy Owls wintering on the prairies is greater in females and older individuals and may contribute to sex-based mortality is available at http://www.aoucospubs.org/doi/abs/10.1642/AUK-16-60.1.

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. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

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Tracing the Evolution of Bird Reproduction

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Avian reproductive strategies have gone through a series of stages, from dinosaurs to today. Image credit: D. Anduza

What really did come first—the chicken or the egg? Birds’ reproductive biology is dramatically different from that of any other living vertebrates, and ornithologists and paleontologists have long wondered how and when the unique features of bird reproduction originated. A new Review in The Auk: Ornithological Advances examines answers from three sources—modern birds, fossils of primitive birds, and fossils of the dinosaurs from which birds are descended—to shed new light on the subject.

All modern birds share certain reproductive features, such as a single functional ovary and the practice of incubating their eggs through direct contact. Analysis of the bird family tree also suggests that early birds built simple, open nests on the ground and that their young were “precocial,” meaning they were well-developed and almost ready to fend for themselves when they hatched. Those dinosaurs close to the ancestry of birds shared some of these traits, but they had two functional reproductive tracts, and their eggs were smaller relative to their body size and more elongated than those of modern birds.

Fossils of primitive birds and eggs from the Mesozoic era place them midway between their dinosaur ancestors and their modern descendants, with eggs between those of pre-avian dinosaurs and modern birds in term of size and shape. In this way, David Varricchio and Frankie Jackson of the Montana State University are able to trace the evolution of bird reproduction through a series of distinct stages, from pre-avian dinosaurs to the birds of today.

“Reproduction in modern birds is distinct among living vertebrates. Many aspects of this reproduction mode trace their origin to theropod dinosaurs such as Oviraptors and Troodontids, but not really beyond them to more distantly related dinosaurs,” according to Varricchio. “Interestingly, reproduction in the most common group of Mesozoic birds is very similar to that of these dinosaurs, and so still differs from modern birds. Consequently, modern birds stand apart from Mesozoic birds, and perhaps this contributed to their surviving the end-Cretaceous extinction event.”

Reproduction in Mesozoic birds and evolution of the modern avian reproductive mode is available at http://www.aoucospubs.org/doi/full/10.1642/AUK-15-216.1.

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. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.