AUTHOR BLOG: Tracking Yosemite’s Spotted Owls

_MG_8939 (2)

Tracking Spotted Owls in Yosemite National Park. Photo credit: S. Scherbinski

Stephanie Eyes

Linked paper: California Spotted Owl (Strix occidentalis occidentalis) habitat use patterns in a burned landscape by S.A. Eyes, S.L. Roberts, and M.D. Johnson, The Condor: Ornithological Applications 119:3, August 2017.

In 2005, I happily discovered the Student Conservation Association and that I could be an intern studying California Spotted Owls in Yosemite National Park. I accepted the internship and worked on a PhD student’s project investigating the effects of fire on California Spotted Owl occupancy. The final results from this study revealed that owl occupancy rates were similar between burned and unburned forest, but led to questions about how owls use the mosaic of post-fire patches. In 2010, the former PhD student, my graduate advisor, and I began our efforts to understand this question by capturing owls and affixing radio transmitters to them with the help of several technicians over the course of the three field seasons. By attaching a radio transmitter, we were able to use radio telemetry to triangulate the position of owls during nocturnal foraging bouts. Specifically, we wanted to know how owl foraging patterns are influenced by fire severity, fire-created edges, and other factors such as topography or distance to stream or nest/roost site.

After owls were captured, we set up our telemetry stations along the trails and roads surrounding our known owl roost sites. We went out in teams of two, each armed with a headlamp and an antenna, and worked to locate the owls within our burned sites. Once we initially identified that an owl was present with our antenna, we would split up, one person racing ahead so that we could get three different readings within ten minutes, each separated by about 200 meters, before the owl moved to a new foraging site. While I was relatively experienced with daytime radio telemetry, these nocturnal trail surveys posed a new challenge I enjoyed overcoming, and one time we encountered a curious mountain lion also using the trail searching for (I hoped!) something else.

Whenever we surveyed these trail sites, I remember wondering what the owl was hunting in the burned mosaic of forest patches at the moment that we were trying to pinpoint its location. I’m hoping all my wondering what they were eating will encourage me to go through all the pellets we found in burned forests!

After all the data was collected and analyzed, we learned that owls exhibited habitat selection for locations near roosts and edge habitats, as well as weak selection for lower fire severities. Our results highlight the importance of sustaining forests burned with a mosaic of fire severities with smaller patch sizes of high severity fire. Maintaining this complex mosaic of forest patches and focusing on protecting roost site locations may help sustain California Spotted Owls in the greater landscape.

AUTHOR BLOG: ‘Bare Parts’ are an Important but Underappreciated Avian Signal

AUK-16-136

Two female American Goldfinches in an antagonistic interaction. Bill-color, derived from carotenoids, is a signal of dominance among female goldfinches but not among males. Image credit: K. Tarvin

Erik Iverson

Linked paper: The role of bare parts in avian signaling by E.K. Iverson and J. Karubian, The Auk: Ornithological Advances 134:3, July 2017.

Birds are well-known for being among the most colorful of all animals, with many species displaying striking, brightly-colored feathers. Scientists have long wondered why color is so important to fitness, and hundreds of studies have been published on the relationships between plumage and traits such as age, physiological condition, reproductive success, and attractiveness to mates. However, there is a growing awareness that plumage is not the only important site of coloration among birds; there is also considerable variation within and between species in the color of bills and in bare skin such as legs, feet, ceres, or wattles. Yet compared to plumage, these ‘bare part’ ornaments have received relatively little attention; a 2006 review of carotenoid coloration in birds, for instance, identified only 14 studies of bare parts versus 130 studies of plumage.

Unlike plumage, bare part color has the potential to be highly flexible. For example, carotenoid-based bare parts can lose their color within days of food deprivation or within hours of stress. Amidst growing suggestions that changes in bare part color could have important implications for signaling, one of the authors, Jordan Karubian, was studying Red-Backed Fairywrens (Malurus melanocephalus) in Australia. In this species, males either acquire a territory and display black breeding plumage and bills, or stay dull and serve as helpers at the nest. Jordan noticed that when a breeding male died and a dull male took over its vacancy, the dull male’s bill would darken within several weeks. Experiments confirmed this effect and showed that dull males with newly black bills also had testosterone levels comparable to birds with black plumage. I joined Jordan’s lab as an undergraduate and studied fairywrens as well, and when I was looking for a topic for an honors thesis Jordan suggested that bare parts were an expanding area in need of a review. That thesis grew and grew, eventually becoming my master’s work and encompassing 321 published studies of bare-part coloration and signaling.

Our review shows that despite the research focus on plumage, bare part signals might be more common than plumage-based ones and are an important visual signal in many species that lack bright plumage altogether. Carotenoids, melanin, and structural colors are all flexible in bare parts, and rapid blood flushing through skin can change color even more rapidly. Bare part color provides up-to-date information about a signaler, allowing competitors, mates, and offspring to adjust their strategies and maximize their fitness. Carotenoid-signaling with bare parts may also be less costly than with plumage, allowing signaling by females and non-breeding males. In species where both plumage and bare parts of the same color exist, the two are likely to be ‘multiple messages,’ conveying different aspects of condition or targeting different audiences. We believe that more careful and extensive characterization of bare part coloration will contribute greatly to our understanding of this underappreciated dynamic signal, and help inform a more inclusive theory of animal communication.

AUTHOR BLOG: Tell me a story! A plea for more compelling conference presentations

Kathryn Langin

Linked paper: Tell me a story! A plea for more compelling conference presentations by K.M. Langin, The Condor: Ornithological Applications 119:2, May 2017.

At one point during last year’s North American Ornithological Conference, I found myself rushing down the hallways to catch a talk by a senior scientist whose research I have long admired. As I took my seat and he began speaking, I was immediately struck with the thought: “Darn, why did I make this mistake again?”

My mistake? Deciding to attend his talk and, in the process, failing to remember that I loathe his presentation style. The slides are always filled to the brim with volumes of text and a seemingly endless number of teeny-tiny figures. And despite going through them at a sprinter’s pace, he somehow fails to finish in the allotted fifteen minutes. It happens every time. The audience experience is akin to watching an action-packed commercial but, in the end, having only a vague sense of what was being advertised.

That incident and many others propelled me to write the Commentary “Tell me a story! A plea for more compelling conference presentations,” published this week in The Condor: Ornithological Applications. In it, I argue that scientists should spend less time trying to impress their audience with mountains of data and more time implementing principles of good storytelling. I know this probably elicits a negative reaction in some readers, but hear me out.

Stories aren’t a mode of communication restricted to fictional tales. They are the most effective way to package information so that others can process and remember it (which is really the whole point of communication, right?). It’s difficult to recall a series of random facts; it’s much easier to recall the details of an engaging story.

The nice thing about storytelling is that it is a natural fit for the scientific process. Dr. Randy Olson, author of the book Houston, We Have a Narrative: Why Science Needs Story, defines a story as “a series of events that happen along the way in the search for a solution to a problem.” Sound familiar? As scientists, we are always in hot pursuit of a solution to a problem, but unfortunately we don’t always present our research that way.

So how can we change that? For starters, it’s not sufficient to package information in a logical order with a beginning (introduction), middle (methods and results), and end (conclusions). That’s obviously helpful, but I argue in the paper that you need to go a step further and develop a compelling plot—something that compels your audience to follow along with your journey of discovery. That can be accomplished by clearly articulating a problem to be solved and spending time convincing the audience why they should care about the problem in the first place.

In his book, Dr. Olson outlines a strategy that I find particularly helpful. He suggests framing your story’s plot by proclaiming something that scientists know and something else that scientists know, but then pointing out a critical unsolved problem or point of debate that, therefore, highlights a need for your particular study. He calls this his “and, but, therefore” template, which contrasts with the template used by many scientists: one that strings along a series of facts with “and, and, and” statements. There’s no drama in “and, and, and” statements, but there is with the “and, but, therefore” framework.

A key advantage of Dr. Olson’s approach is that—by setting the stage in an informative and captivating manner—you can bring your entire audience with you on your journey, not just the people who already understand and appreciate your field and study system. And that should be the ultimate goal: to engage the widest fraction of your audience as possible.

The ornithological community is doing important and interesting science, but we don’t always do a great job communicating it, even amongst ourselves. In my paper, I argue for more storytelling, but I also discuss a greater range of strategies for giving effective presentations, including the benefits of visually-engaging slides. I don’t expect everyone to agree with me, but it is my hope that this opinion piece will generate thought and discussion about how to best communicate our science. We can’t afford to let important research be lost in a sea of ineffective communication.

AUTHOR BLOG: Common Murre Parenting 101: How to Negotiate for an Easier Job

IMG_3895

Researcher Linda Takahashi observes nesting murres. Photo credit: N. Oberlander

Linda Takahashi

Linked paper: Turn-taking ceremonies in a colonial seabird: Does behavioral variation signal individual condition? by L.S. Takahashi, A.E. Storey, S.I Wilhelm, and C.J. Walsh, The Auk: Ornithological Advances 134:3, July 2017.

When mates share parenting duties, conflict can arise over which one performs the hardest jobs. Common Murres are monogamous long-lived seabirds that raise only one chick each year. Extensive contributions from both parents are obligatory for successful chick fledging: Chicks are rarely abandoned, and murres are great parents. Throughout the three week chick-rearing period, one parent remains at the nest site, brooding and defending the chick, while the other is most often away from the colony foraging.  Murres have the highest wing loading of any flying bird, and so foraging far away from the colony, which is often necessary in years of reduced capelin availability, is energetically costly. Remaining in the colony with the chick is simply the easier job.

All things being equal between the murre parents, we’d expect that they would take turns and share the harder job of chick provisioning. For the most part, this is indeed what they do. One mate returns to the colony with a fish, feeds the chick, and the takes over brooding duties while the former brooder leaves. We called this a regular nest relief. However, some nest reliefs are irregular, such as when the returner comes back without a fish or the brooder doesn’t give up the chick, causing the returner to leave again to forage. We wondered if variation in nest reliefs was related to the relative physiological condition of the partners and whether changes in specific behaviours that occur during the nest relief ceremony were indicators of the partners “negotiating” with each other for the easier parental job.

Until our study, little focus had been given to the often-subtle behaviours shown by murres during nest relief (turn-taking) ceremonies. We looked at 16 pairs of Common Murres breeding in Witless Bay, Newfoundland, Canada, in 2009, a year with particularly low availability of capelin, the preferred forage fish. Pairs were identified by colour bands and nest location on the cliff. From dawn to dusk, we sat in a tiny observation blind and recorded murre behaviors with either a camcorder or an event logger. Specifically, an interaction began when a returning bird arrived at the nest, typically with a fish, and joined its chick-brooding partner, and it ended when one of the pair departed. We noted whether the parents traded roles and recorded their patterns of allopreening and bill-fencing. We also examined the relationships between murre condition—specifically, body mass and lipid metabolite levels (as measured by beta-hydroxybuterate)—and behavioural variation during turn-taking.

We found that irregular turn-taking ceremonies took longer than regular ones and had either delayed or non-synchronous allopreening. When a returning partner came to the nest without a fish, it began allopreening sooner than both the brooding partner and birds that returned with a fish. These “no fish” irregular nest reliefs took the longest of all, and brooders appeared to resist or delay leaving the colony. In cases where there was no exchange of duties, i.e., the brooder remained in the colony, rates of allopreening by the brooder were significantly lower than they were in all other types of turn-taking ceremony. Birds with higher overall chick-feeding rates brought fish on more visits than other birds, suggesting that that they were higher-quality individuals. Furthermore, brooding birds in relatively better condition departed the colony sooner after their mate fed the chick compared to those in relatively worse condition. We suggest that variation in allopreening allows mates to communicate with each other regarding their own condition, and, if that condition is poor, to negotiate for the easier parental duty, i.e., brooding.

Why would murres benefit from responding to signals about their mates’ condition? Since murres typically retain their mates for several years, parental investment theory predicts that it is in an individual’s best interest to preserve their mate’s current and future body condition as well as their own. Deterioration of a mate’s condition could lead to nest abandonment or even compromised survival. This paper shows that variation in ceremonies is one way to make information available to mates. Thus, behavioural variation during the ceremony can signal individual condition and be a means to negotiate parental roles.

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

AUK-16-134

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.

AUK-16-134 2

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.

AUTHOR BLOG: Tracking Semipalmated Sandpiper Migration

SESA-NomeAK-Bwinn (3)

Photo credit: B. Winn

Stephen Brown

Linked paper: Migratory connectivity of Semipalmated Sandpipers and implications for conservation by S. Brown, C. Gratto-Trevor, R. Porter, E.L. Weiser, D. Mizrahi, R. Bentzen, M. Boldenow, R. Clay, S. Freeman, M.-A. Giroux, E. Kwon, D.B. Lank, N. Lecomte, J. Liebezeit, V. Loverti, J. Rausch, B.K. Sandercock, S. Schulte, P. Smith, A. Taylor, B. Winn, S. Yezerinac, and R.B. Lanctot, The Condor: Ornithological Applications 119:2, May 2017.

The Semipalmated Sandpiper (Calidris pusilla) is a small shorebird, most commonly seen on migration along the coastlines of the eastern United States. It is historically one of the most widespread and numerous shorebird species in the Western Hemisphere, breeding across the North American Arctic tundra, but major population declines have been documented in the core of the nonbreeding range in northern South America. Breeding populations have also declined in the eastern North American Arctic, but appear to be stable or increasing in the central and western Arctic. To help understand what is causing the declines and work toward conservation of this species, we set out to track migration routes and stopover sites using light-level geolocators, a relatively new technology which determines the bird’s position on earth by measuring the length and timing of daylight throughout the year. The major challenge to using these tags is that you have to catch the bird once to put on the geolocator and then again the next year to retrieve it, which requires finding the same bird again in the vast arctic tundra. Luckily, they tend to return to the same breeding areas the next year.

Our large group of 18 partner organizations worked collaboratively to carry out the study across the entire North American Arctic from Nome, Alaska, to Hudson Bay, and we attached 250 geolocators to birds by mounting expeditions to 8 different field sites. Our field crews faced challenging conditions, working in the Arctic where the weather is always unpredictable and where both grizzly bears and polar bears regularly visit field sites. We repeated expeditions the next year to each site, and recovered 59 of the units by recapturing birds. The treasure trove of data showed migration routes and stopover sites from the entire year in the life of each bird, and showed that birds breeding in the eastern Arctic wintered in northeastern South America. Birds from eastern Alaska and far western Canada wintered from Venezuela to French Guiana. Central Alaskan breeders wintered across a very wide range from Ecuador to French Guiana. Birds that bred in western Alaska wintered mainly on the west coasts of Central America and northwestern South America, outside the nonbreeding region in which population declines have been observed.

Our results confirm that Semipalmated Sandpipers that breed in the eastern Arctic and use the Atlantic Flyway also use the areas in South America where population declines have been detected, suggesting that declines may be concentrated in populations along the Atlantic Flyway and in the eastern Arctic. However, because some birds from sites as far west as Barrow, Alaska, also used the areas in northeastern South America where declines have occurred, further work is needed to localize the geographic areas used by declining populations, and therefore the potential causes for the declines. We identified several new stopover and wintering areas, where implementing conservation actions to preserve the habitats used by Semipalmated Sandpipers could contribute to protecting the species. We measured a larger impact of geolocators on return rates than has been observed for larger shorebirds, indicating that caution should be used when working with small shorebirds, and that potential new information gains from additional geolocator studies should be weighed against expected impacts on individual survival. Our data also provided new insights about how long birds stay at migration stopover sites, which will be useful to studies that measure and monitor the total size of populations using these sites. Understanding the connections between breeding, migration, and wintering areas for these populations of a widespread yet declining shorebird can help future studies identify the causes of declines and ensure the effectiveness of targeted conservation efforts.

AUTHOR BLOG: A New Look at Altitudinal Migration

AUK-16-228

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