Time-Lapse Cameras Provide a Unique Peek at Penguins’ Winter Behavior

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Gentoo Penguins at a breeding site in winter, as captured by a time-lapse camera. Image credit: T. Hart

Not even the most intrepid researcher wants to spend winter in Antarctica, so how can you learn what penguins are doing during those cold, dark months? Simple: Leave behind some cameras. Year-round studies across the full extent of a species’ range are especially important in polar areas, where individuals within a single species may adopt a variety of different migration strategies to get by, and a new study from The Auk: Ornithological Advances uses this unique approach to get new insights into Gentoo Penguin behavior.

Gentoo Penguins are of interest to scientists because they’re increasing at the southern end of their range in the Western Antarctic Peninsula, a region where other penguin species are declining. Little is known about their behavior during the nonbreeding season, so Caitlin Black and Tom Hart of the University of Oxford and Andrea Raya Rey of Argentina’s Consejo Nacional de Investigaciones Cientificas y Técnicas used time-lapse cameras to examine patterns in Gentoo Penguins’ presence at breeding sites across their range during the off season. They found both temporal and spatial factors driving winter attendance—for example, more Gentoo Penguins were present at breeding sites when there was open water or free-floating pack ice than when the shoreline was iced in, and more Gentoo Penguins were at breeding sites earlier in nonbreeding season than later.

The researchers deployed the cameras at seven sites including Argentina, Antarctica, and several islands. Each camera took eight to fourteen photos per day, and volunteer “citizen scientists” were recruited to count the penguins in each image via a website (penguinwatch.org). Overall, the seven sites fell into three distinct groups in terms of winter attendance, each with its own patterns of site occupation. These findings could have important implications for understanding how localized disturbances due to climate change and fisheries activity affect penguin populations during the nonbreeding season.

“Working with cameras allows us to understand half of this species’ life without having to spend the harsh winter in Antarctica. It has been exciting to discover more about why Gentoos are present year-round at breeding sites without having to handle a single bird,” says Black. “I believe the applications for this technology are far-reaching for colonial seabirds and mammals, and we are only just beginning to discover the uses of time-lapse cameras as deployed virtual ecologists in field studies.”

“What most seabirds do away from their nest is often anybody’s guess. For Antarctic birds, this is compounded by the long periods of darkness that penguins and others must face in the winter,” adds Mark Hauber, Editor-in-Chief of The Auk: Ornithological Advances and Professor of Animal Behavior at Hunter College and the Graduate Center of the City University of New York. “This new research in The Auk: Ornithological Advances on Gentoo Penguins colonies reveals critical year-to-year differences in where the birds are when they are not nesting: In some years, only the most temperate sites are visited, and in other years both southerly and northerly locations are busy with penguins.”

Peeking into the bleak midwinter: Investigating nonbreeding strategies of Gentoo Penguins using a camera network is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-16-69.1.

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.

AUTHOR BLOG: How the ‘Mitey’ Have Fallen: Impacts of Burrowing Skin Mites on Reproduction of an Urban Raptor

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Black Sparrowhawks displaying symptoms of mite infection.

Julia L. van Velden

Linked paper: Negative effect of mite (Knemidokoptes) infection on reproductive output in an African raptor by J.L. van Velden, A. Koeslag, O. Curtis, T. Gous, and A. Amar, The Auk: Ornithological Advances 134:3, July 2017.

Parasites were once considered to be one of the less important factors that limit or regulate animal populations, with the impacts of predators and resource limitation previously receiving far more attention. This lack of attention probably stemmed from the mistaken belief that most parasites have evolved not to harm their hosts too much, because if their host dies, they lose the resource they depend on. We now know, however, that parasites can often strongly affect both a host’s reproduction and survival rates. Our new study published in The Auk: Ornithological Advances adds to this knowledge for a relatively understudied parasite in a wild raptor population.

Knemidokoptes mites are a genus of microscopic skin mites which burrow into the skin of birds and cause the “scaly leg” and “scaly face” conditions that are frequently seen in caged and domestic birds. They also occur in some wild species, particularly passerines. However, these parasites have rarely been recorded on raptors, except on captive birds. Additionally, almost no research has been carried out to investigate the impacts of these parasites on species’ fitness. Our study explored the symptoms of infection and the impact these mites have on the breeding performance of a wild population of Black Sparrowhawks in Cape Town, at the southernmost tip of South Africa.

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Knemidokoptes skin mites.

Black Sparrowhawks are a recent colonist to this mostly urban area, and urban living may come with associated changes in exposure to parasites and pathogens. Our study population has been closely monitored since 2001 and has grown steadily over the years, with the population now containing around 50 breeding pairs each year. In 2007, we started to notice birds in the population with strange symptoms, namely balding heads and scaly lesions on their legs. These birds appeared to be agitated and in poor condition. Post-mortem investigations revealed that, in all cases, birds with these symptoms were infected with the burrowing skin mite (Knemidokoptes spp.). We found that in some years, up to 5% of the Cape Peninsula population was infected, which represents a highly novel finding for a wild population of raptors.

Comparing between the sexes, we also found that mite infection was more frequent for males than females. Higher parasitic infection of males has been found for several other studies in different parasites and may be the result of fundamental biological and behavioural differences. In our population, we suspect that Black Sparrowhawks may become infected by these mites from their prey, possibly domestic chickens, which are known to frequently be infected by Knemidokoptes mites. Like most Accipiters, Black Sparrowhawks pluck their prey before consumption, which may mean they have greater exposure to this parasite than other raptor species, and the fact that males are responsible for hunting throughout the breeding season may explain the male bias in infection.

Most importantly, we found that Black Sparrowhawks that were infected with these mites had considerably reduced breeding success. We compared breeding performance between infected and non-infected birds and also between birds pre- and post-infection. These analyses showed that infection reduced breeding performance by over 50%. This could be because adults become too agitated to incubate or hunt effectively following infection.

We also investigated if this infection was present anywhere else in South Africa and found four hotspots of infection. Three of the infection sites were cities, and thus infection by this mite may be associated with urbanization levels and the additional stresses this may incur. Other research has, however, not yet detected any negative effect of urbanisation on this species’ health.

Our study, the first on Knemidokoptes mites within a wild population of raptors, therefore suggests that this parasite could play a role in limiting the breeding performance of infected populations. Although Black Sparrowhawks are not a species of conservation concern, this study provides important information on the negative role such parasites can play in their host’s reproductive success, which will be important if this infection is found to occur in an endangered raptor species.

Eagles Migrate Through Bad Weather to Arrive in Time to Nest

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A Golden Eagle wearing a GPS transmitter. Photo credit: P. Fusco

Migration is tough, and birds do everything they can to optimize it. How do factors like weather and experience affect the strategies they choose? A new study from The Auk: Ornithological Advances shows that older, more experienced Golden Eagles actually migrate in poorer weather conditions and cover less ground than their younger counterparts, but for a good reason—they’re timing their efforts around raising the next generation of eagles.

Adrian Rus of Boise State University (now at Australia’s University of Sydney), Todd Katzner of the USGS, and their colleagues studied GPS telemetry tracks to evaluate the migratory performance of almost 90 Golden Eagles in eastern North America and determine how performance related to season, age, and weather. Unsurprisingly, eagles flew faster and farther when they had strong tailwinds and thermals to help them along. What was counterintuitive, however, was that older eagles did not cover more ground than younger eagles despite their greater experience. Instead, older eagles migrated in poorer weather conditions and travelled more slowly.

The researchers believe this is because older birds face different pressures than younger birds. Even if the weather is bad and will slow them down, they need to start heading north earlier than young birds that aren’t breeding, because they have to get back to their breeding grounds in time to reclaim their territories and start nesting. “Younger eagles just need to survive the summer, so they can be choosy about when they travel north and only migrate when conditions are really ideal for fast soaring flight,” explains Katzner.

Lead author Adrian Rus, who worked on the study as an undergraduate, enjoyed the challenges involved in analyzing the migration data. “The best part about working on this project was using specialized software to visualize the golden eagle migrations and being able to pair it with meteorological data to answer my biological questions,” he says. “As a result, the project greatly improved my geospatial and statistical analysis skills and was instrumental my current graduate research in animal movement ecology.”

“Rus et al. provide an unusual demonstration of the interaction between migration experience and seasonal environments,” according to Oklahoma University’s Jeff Kelly, an expert on avian migration. “It is likely that the migration experience that older birds have enables them to extend their summer season through early spring and late autumn migration despite declining atmospheric conditions. Rus et al.’s demonstration of this insight into the interaction between age and the migratory environment expands our thinking about the life history tradeoffs that occur across the annual cycle of migrants.”

Counterintuitive roles of experience and weather on migratory performance is available at http://americanornithologypubs.org/doi/abs/10.1642/AUK-16-147.1.

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.

AUTHOR BLOG: A New Look at Altitudinal Migration

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Alice Boyle

Linked paper: Altitudinal bird migration in North America by W.A. Boyle, The Auk: Ornithological Advances 134:2, April 2017.

I became a birder in my early 20s when I moved to Costa Rica to play in the Orquesta Sinfónica Nacional. I didn’t know many people at first, and my Spanish was, shall we say, a work in progress. When I left Canada, I was given a pair of binoculars and the (then) newly published “A Guide to the Birds of Costa Rica” by Stiles and Skutch. Armed with these tools, I would get on a bus headed in a different direction every time I had a day off from my music job. At first I managed to identify only a few of the dozens of species that would pass in riotous mixed flocks. Pretty soon I realized that I had to focus on looking and taking notes, only later to pore over the book to figure out what I had seen. While those evening book sessions were occasionally frustrating (“Dang… I should have checked if that flycatcher had one or TWO wing bars!”), I also enjoyed reading the eloquent descriptions of bird behavior and soon found myself engrossed in tropical natural history. One of the things that puzzled me from the start were descriptions of the seasonal migrations of birds within that tiny, lovely, benign country. I grew up in a place where bird migration seemed not only logical, but frankly the ONLY sensible thing to do in winter. But why would some birds move up and down mountains each year in a place where the weather is always warm and food hangs from the trees wherever you go?

This question ultimately became the topic of my PhD many years later, and I did get some satisfying answers (full details here). But one unsatisfactory aspect of my chosen topic was that few other researchers were asking similar questions in other parts of the world. What common themes from my tropical work might hold true for other regions? What about North American birds? How common are these altitudinal migrations in our mountains? What else is known about them? Finally, in this article, I have attempted to summarize that knowledge. It turns out that we have LOTS of birds in North America that make similar types of movements. In fact, roughly the same proportion of the North American avifauna migrate up and down mountains as does the Costa Rican avifauna—20% to 30% depending on how you count it. With the exception of the Himalayas, reports from other avifaunas seem consistent with this figure. The higher latitude of North America makes things interesting, creating varied combinations of seasonal movements along both elevational and latitudinal gradients, and several of the North American species make movements that stretch our tidy migration terminology in complex ways. There is a reason I had trouble as a grad student finding this literature, however. Much of the information, now summarized in the Birds of North America life history series, was originally reported in bird atlases, Masters theses, or dated natural history accounts. Furthermore, despite early naturalists’ interest in the topic, few authors have cared to document patterns or tried to understand causes of these movements in recent years.

Why might this be so? Part of the reason might have to do with geography; there are more ornithologists in the flatter and more populated eastern portion of the continent compared to the topographically complex west, and this fact may have steered our collective research interest in some way. Part might have to do with the perception that these are not “real” migrations. Certainly the short distances many altitudinal migrants traverse are not the jaw-dropping feats of athleticism displayed by Red Knots, Arctic Terns, or Blackpoll Warblers. But I argue that they are real in many important respects: they involve seasonal return movements between breeding and non-breeding areas on predictable schedules. The fact that such movements are often partial (not all birds migrate), facultative (not genetically hard-wired), and short-distance actually makes them more attractive subjects for many types of migration research. We have far better chances of determining what ecological conditions tip the cost-benefit balance toward migrating in species that have built-in control groups in the form of resident individuals. Furthermore, the more “messy” movements are undeniably a part of the rich diversity of strategies that animals use to cope with a constantly shifting environment. If we are to protect our avifauna for future generations, understanding these movements will be as important as understanding the marathon flights of the migration poster children. Perhaps this review will inspire a blossoming of interest in the birds who make mountains their home.

Find out more:
www.aliceboyle.net
On Twitter: @birdfiddler
Learn about what we do in the Boyle Lab by following our YouTube channel and Flickr stream

Endangered Ibises Benefit from Joining Egret Flocks

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A Little Egret (far left) forages with endangered Crested Ibises. Photo credit: N. Zhao

Birds benefit from flocking together—even when they’re not of a feather. According to a new study in The Auk: Ornithological Advances, China’s endangered Crested Ibises benefit from joining forces with other, more visually-oriented bird species while searching for food.

Joining mixed-species flocks can reduce birds’ risk of predation while boosting their foraging opportunities, but it can also expose them to competition and disease, and little research has been done on what this means for birds such as ibises that rely on their sense of touch to find food. Yuanxing Ye and Changqing Ding of the Beijing Forestry University and their colleagues studied the behavior of Crested Ibises foraging with and without Little Egrets in central China’s Shaanxi Province, recording the birds’ behavior with a digital video camera to determine whether they picked up on social cues from the other species. They found that ibises in mixed-species flocks became alert to threats sooner, suggesting they felt less at risk when mingling with the more visually-oriented egrets.

Crested Ibises were once believed to be extinct in the wild, until seven birds were discovered in a remote area of China in 1981. Ye and his colleagues believe this new information about their foraging behavior could benefit ibis conservation. “Developing habitat conditions that favor mixed-species flocks may reduce the perception of risk by ibises due to the early warning effects of egrets, particularly in habitats with high levels of predation or disturbance,” according to Ye.

“Mixed-species flocks are a common occurrence in birds, but little is known about the costs and benefits of joining such groups when species differ in their foraging tactics,” adds the University of Montreal’s Guy Beauchamp, an expert on group living in birds. “In this case, ibises benefitted from joining another more visually-oriented species in that they detected threats more quickly. This study shows how detailed behavioral observations can help us understand why species forage in groups and also join other species.”

What makes a tactile forager join mixed-species flocks? A case study with the endangered Crested Ibis (Nipponia nippon) is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-16-191.1.

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.

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AUTHOR BLOG: Bringing Mitochondria into Species Concepts

Geoffrey Hill

Linked paper: The mitonuclear compatibility species concept by G.E. Hill, The Auk: Ornithological Advances 134:2, April 2017.

A couple of years ago I was at the Bentsen State Park hawk watch tower with a dozen other birders when the topic of species boundaries came up. No one knew me or that I was a professional ornithologist—I was deep undercover as a mediocre birder—so I just listened to the conversation. Someone suggested that the “experts” changed species boundaries periodically so that new field guides would have to be printed and bought. The not-so-subtle suggestion was that the checklist committee was in the pockets of powerful publishers. Then it was suggested that researcher elites manipulated the system to get government money. Everyone quickly reached consensus that both of these views were correct. From that conversation, it would seem that scientists have not been very effective at conveying to the public the rationale for changes to the checklist. But maybe a skeptical public is not surprising given that some professional ornithologists are also not enamored with how species boundaries of birds are demarcated. This uncertainty regarding what is or is not a species could simply reflect the reality that at the tips of the branches of the tree of life, species boundaries are nebulous. But I don’t think that is correct. I agree with Ernst Mayr’s conclusions that species are real and fundamental biological entities. I’m convinced that the problem with the current approach to assessing species boundaries lies in a poor understanding of the process of speciation leading to an incomplete and confused species concept.

I lived the first fifty years of my life without offering any opinion about the process of speciation or species boundaries, and I had no plans to ever wade into the morass. It was therefore quite unexpected when I fell head first into the deep end of the speciation controversy by proposing a new definition for how to define an avian species, published as an opinion piece in The Auk. This new speciation concept arose not from phylogeographic studies—the genesis of all previous species concepts—but from the study of mating patterns in relation to colorful feathers (see Hill and Johnson 2012). Sexual selection and speciation have always been closely associated topics in evolutionary biology, but what I realized about five years ago is that both of these fundamental evolutionary processes emerge as a necessary outcome of the critical need for coadaptation between mitochondrial and nuclear genes and that mitonuclear coadaptation is the foundation of any comprehensive species concept. Before I explain what I mean by “mitonuclear coadaptation,” however, I need explain current dogma for recognizing species.

Whether it is explicitly stated or not, decisions regarding species boundaries are based on a species concept, and the Biological Species Concept currently being followed by the American Ornithological Society checklist committee was proposed by Ernst Mayr about 75 years ago, long before the age of modern genomics. As a matter of fact, the current species concept was written before biologists even knew that mitochondria have DNA that is inherited independently from the nuclear DNA.

It turns out the knowing about mitochondrial DNA is very important because mitochondrial DNA codes for components of the electron transport system, which is the biochemical machine that generates most of the energy for birds, mammals, and other complex life. But mitochondria only carry a few genes—not nearly enough to code for the entire electron-transport system—so much of the system is encoded by nuclear DNA, with the products moving over to the mitochondria to co-function with the products of mitochondrial genes. Having two distinct genomes coding for components that have to work together in a fully coordinated manner means that these genomes have to be coadapted; put another way, the genes in the mitochondria and nucleus have to coevolve so that their products are matched in physical shape and complementary of function. When populations become isolated, their mitochondrial and nuclear genes can coevolve to be different than the coevolved mitochondrial and nuclear genes of any other population such that they cannot be mixed without incompatibilities and fitness loss. What I propose in my opinion paper is that it is uniquely coadapted sets of mitochondrial and nuclear genes that define a species and that make hybrid offspring resulting from pairings between species less viable, thereby maintaining species boundaries.

Currently, it is not possible to assess the mitonuclear compatibility of any two populations of birds, although by simple extrapolation of advancing technology we will soon have such capability. What we currently have is information on the mitochondrial genotype of many species of birds, including many populations that are potentially distinct species. I propose that uniquely co-adapted mitonuclear genotypes necessarily involve unique mitochondrial genotypes. Thus, mitochondrial genotype becomes an excellent and available proxy for species boundaries.

Many biologists already look to mitochondrial genotypes when assessing species status.  My theory simply provides stronger justification for placing more emphasis on mitochondrial genotypes and less emphasis on nuclear genotypes. Indeed, advocates of DNA barcoding assert that most species can be unambiguously diagnosed by mitochondrial gene sequence, and my theory potentially explains why.

As with any new idea, this hypothesis for the process of speciation and nature of species boundaries must be tested. Whether the mitochondrial compatibility species concept proves to be accurate or an overstatement, ornithology will benefit by considering mitonuclear interactions when they ponder species boundaries.

Redefining “Species”: New Species Concept Based on Mitochondrial & Nuclear DNA Coadaptation

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A hybrid “Brewster’s” warbler. Photo credit: L. Spitalnik

What is a species? Biologists—and ornithologists in particular—have been debating the best definition for a very long time. A new commentary published in The Auk: Ornithological Advances proposes a novel concept: that species can be defined based on the unique coadaptations between their two genomes, one in the nuclei of their cells and the other in their mitochondria.

All animals have two sets of genes, one in the cell nucleus and one in organelles called mitochondria, and these two sets of DNA work together to enable cellular respiration and energy production. If they’re mismatched, the result is reduced energy output and increased production of damaging free radicals. While the most commonly used species definition is based on the idea that isolated populations slowly accumulate changes in their nuclear genes that make interbreeding impossible, Auburn University’s Geoffrey Hill proposes a new twist on the species concept—that speciation is really the divergence of sets of coadapted mitochondrial and nuclear genes. Interspecies hybrids, his theory suggests, have reduced fitness due their mismatched genomes’ reduced ability to work together in the cell.

Past studies have shown that mitochondrial genotype tends to be very good at showing species boundaries between birds. This “mitonuclear compatibility species concept” helps explain the fact that the abrupt transitions between mitochondrial genotypes at species boundaries correspond with abrupt transitions in songs, plumage patterns, and female mating preferences. Interestingly, two closely related species that have recently been documented to have extensively intermingled nuclear genes—Blue-winged and Golden-winged warblers—also show an abrupt transition in mitochondrial genes.

“Almost all ornithologists who write and think about avian speciation study phylogeography—the geographical distribution and genetic structure of bird populations,” says Hill. “In contrast, I study bird ornamentation and, particularly, bird coloration. It was the discovery that ornaments signal mitochondrial type that led to my sudden realization that mitochondrial type—or, more accurately, coadapted sets of mitochondrial and nuclear genes—define species boundaries. I don’t think I would have ever seen the pattern if I had come at the question from a phylogeographic perspective.”

“This is an intriguing and controversial idea—that mitonuclear incompatibilities could be so central to generating new avian species—and I see this as a call for more research into how these incompatibilities might manifest themselves in young species,” says avian evolutionary biologist David Toews of Cornell University. “The functional aspects of mitochondrial genes have, in particular, received little attention from the ornithological community, and it will be interesting to see how these ideas play with additional empirical studies going forward.”

The mitonuclear compatibility species concept is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-16-201.1.

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.

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