AUTHOR BLOG: Ancient Fossil Bones of a Recently Extinct Cormorant

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.

The new and heretofore unfigured species of the birds of North America

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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Spotted Owl (Photo Credit: Alan Dyck)

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

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

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

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

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

Nominees for BioOne Ambassador Award

The Auk and The Condor have each nominated a recent author for BioOne’s inaugural Ambassador Award, which will recognize “early career authors working to communicate the importance and impact of their focused research to communities beyond their fields of expertise.” Each of up to five winners will receive a $1000 cash award. More information can be found on BioOne’s website.

The Auk has nominated Emily Williams, lead author of the recent paper Patterns and correlates of within-season breeding dispersal: A common strategy in a declining grassland songbird (press release).

The Condor has nominated Andrew Dennhardt, lead author of the paper Applying citizen-science data and mark–recapture models to estimate numbers of migrant Golden Eagles in an Important Bird Area in eastern North America (press release).

We wish Emily and Andrew luck as the selection process for the awards continues!

Terns Face Challenges When They Fly South for Winter

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

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

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

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

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

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

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

Long-Term Study Reveals Fluctuations in Birds’ Nesting Success

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

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

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

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

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

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

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union, which merged with the Cooper Ornithological Society in 2016 to become the American Ornithological Society. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.