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The official blog of ornithology journals The Auk and The Condor
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Homebody Tendencies Put Hawaiian Gallinules at Risk

Wed, 10/24/2018 - 17:21

Hawaiian Gallinules’ limited dispersal may be putting them at risk. Photo credit: J. Underwood

The Hawaiian Islands are home to a range of unique, endangered bird species. Many waterbirds such as the Hawaiian Coot and Hawaiian Gallinule have been recovering in recent decades thanks to intensive wetland management, but past declines have left them with reduced genetic diversity. A new study from The Condor: Ornithological Applications looks at what the birds’ genes can tell us about their behavior today and finds that one species’ lack of wanderlust may be putting it at greater risk.

The U.S. Fish and Wildlife’s Jared Underwood and his colleagues trapped birds on Oahu and Kauai and took blood, tissue, and feather samples. Genetic analysis conducted at the U.S. Geological Survey by Sarah Sonsthagen and colleagues showed that Hawaiian Coots disperse regularly between islands, while Hawaiian Gallinules do not. The researchers believe that Hawaiian coot populations in some wetlands are reaching the maximum they can support, which is one factor causing them to leave in search of new territories. Historical evidence suggests that gallinules also moved around frequently prior to population declines, so either their behavior has changed, or, unlike the coots, they have yet to reach local carrying capacities.

“The Common Gallinule as a species is considered quite vagile—that is, it tends to move around a lot—so it was surprising to find a high level of genetic structure between two islands separated by only 175 kilometers,” says coauthor Jared Underwood. “Other Common Gallinule subspecies found in the Pacific frequently move between islands that are separated by greater distances.” Hawaiian Gallinules’ homebody tendencies put them at greater risk from severe one-off events like hurricanes, which could wipe out an entire island’s worth of birds. Their lack of gene flow also means that populations on individual islands need to be larger in order to be viable long-term.

Despite recent population gains, the researchers warn that rising seas, diseases, and introduced predators continue to threaten both species. “A key component of the resilience and persistence of species and populations is the retention of genetic diversity,” adds Underwood. “Information regarding the genetic structure for each species will allow managers to design different strategies and criteria for the species’ recovery.”

Interisland genetic structure of two endangered Hawaiian waterbirds: The Hawaiian Coot and Hawaiian Gallinule is available at http://americanornithologypubs.org/doi/full/10.1650/CONDOR-18-98.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology, published by the American Ornithological Society. For the past two years, The Condor has had the number one impact factor among 27 ornithology journals.

AUTHOR BLOG: Saving Saltmarsh Sparrows will help other species, too

Wed, 10/24/2018 - 17:21

Chris Elphick

Linked paper: Evaluating a focal-species approach for tidal marsh bird conservation in the northeastern United States by B.T. Klingbeil, J.B. Cohen, M.D. Correll, C.R. Field, T.P. Hodgman, A.I. Kovach, B.J. Olsen, W.G. Shriver, W.A. Wiest, and C.S. Elphick, The Condor: Ornithological Applications 120:4, November 2018.

Salt marshes in the northeastern USA are getting wetter, increasing the risk that the nests of marsh-breeding birds will be flooded during high tides. Photo credit: Chris Elphick

Saltmarsh Sparrows are in trouble. They are found only in the eastern USA and—as their name suggests—occur only in salt marshes, nesting primarily in the higher elevation portions that are dominated by saltmeadow cordgrass (Spartina patens) and where the risk of nests flooding is lowest. With rising sea levels and increasing storm surges, however, that risk is rising. Since the 1990s, the global population of Saltmarsh Sparrows has declined by about 75%, and demographic studies suggest that extinction is likely by mid-century. Marshes are also changing, with a shift towards vegetation characteristic of wetter conditions, supporting the idea that sea level rise is responsible and that flooding risk for the birds is increasing.

The good news is that people are starting to take notice. The species is considered globally endangered by BirdLife International, it is being assessed for listing under the US Endangered Species Act (ESA), and it is the subject of considerable attention by the Atlantic Coast Joint Venture, which represents most of the key management agencies in states where the species occurs.

Saltmarsh Sparrows, of course, are not the only birds that use salt marshes in eastern North America. Black Rails have already disappeared from much of the East and were recently proposed for ESA listing; Clapper Rails and Nelson’s Sparrows are also declining in the northeastern USA, the only region for which there are comprehensive, large-scale surveys; and other salt marsh specialists nest in similar conditions and will potentially face a similar fate in coming decades.

Conservation for Saltmarsh Sparrows (right) is likely to benefit most other salt marsh specialist birds nesting in the northeastern USA. An exception is Nelson’s Sparrow (left), which has limited range overlap and will require separate conservation actions. Photo credit: Chris Elphick

A key question, then, is whether conservation focused on Saltmarsh Sparrows will also benefit these other species. Conservation biologists have long debated the pros and cons of management focused on individual species. Arguably, centering conservation on an individual species can help garner conservation support that will have ecosystem-wide benefits. At the same time, if the chosen species does not adequately represent the entire suite of species (or other ecosystem properties) that one wants to protect, then the endeavor will fail. In our new paper, we set out to test whether Saltmarsh Sparrows can play this role.

Using the conservation planning software MARXAN, we prioritized salt marsh patches for five bird species that nest in salt marshes across the ten states in which Saltmarsh Sparrows breed.  These species are those most dependent on salt marshes and most likely to be affected by changes to the habitat. (Black Rail, the sixth species in this group, is now so rare in these states that it was not included.) We found that land protection scenarios focused on Saltmarsh Sparrows are more effective at protecting the entire suite of species than scenarios focused on any of the other individual species. Conserving areas that support the bulk of the current Saltmarsh Sparrow population will also protect large (>50,000) populations of all other species except Nelson’s Sparrow. Similar planning based on Clapper Rails—the other declining species—performed much worse, while multispecies combinations performed no better. Nelson’s Sparrow would not be protected well by prioritizing based on any of the proxy species considered, which is not surprising, given the limited overlap between the range of this species and the other four.

Of course, showing that conservation focused on Saltmarsh Sparrows will benefit other salt marsh specialist birds is only a partial answer to the question of whether they are a good focal species for long-term conservation of salt marshes. Birds that use these marshes outside the breeding season, other types of organisms, and the full range of other ecosystem services that marshes provide also warrant consideration. It is clear, however, that work designed to protect sparrows has good potential to benefit some of the other high-priority conservation targets. And given the reliance of Saltmarsh Sparrows on high-elevation marsh—the portion of the system that seems to be most vulnerable to losses due to sea level rise—it appears likely that other organisms that use this habitat will also benefit.

Getting to the Root of Long-Term Tree Swallow Declines

Thu, 10/18/2018 - 10:15

Kent Island’s Tree Swallow population has collapsed as immigration from the mainland has declined. Photo credit: B. Woodworth

Aerial insectivores—birds that hunt for insect prey on the wing—are declining across North America. Conserving vulnerable species such as these requires a good understanding of the factors impacting them at every stage of life. Juveniles and adults, for example, may face different threats and die at different rates. Two new studies from The Condor: Ornithological Applications take a deep dive into the demographic factors behind declining populations of Tree Swallows and show that although specifics may vary between locations, action is needed to address environmental changes affecting these birds across their geographic range.

Queen’s University’s Amelia Cox and her colleagues used a dataset from a swallow population in southeastern Ontario that was monitored from 1975 to 2017, while Bowdoin College’s Liam Taylor and his colleagues looked at data from a population from an island off the coast of New Brunswick that was monitored from 1987 to 2010. Having access to detailed long-term data allowed both sets of researchers to do demographic analysis and determine which life stages were having the largest impact on local population declines. In Ontario, overall declines were driven primarily by drops in overwinter survival and the rate at which swallow chicks successfully left the nest. On Kent Island, analysis showed that the population was dependent on immigration from the mainland, which dropped as mainland populations declined throughout the region. Over the course of the study, the Kent Island population plummeted from 202 adult birds to only 12.

Cox and her colleagues believe that increasingly unfavorable weather conditions and declines in insect availability may be behind the demographic shifts they found. “I hope that our results will spur more research into the environmental causes of Tree Swallow declines and declines of other similar species. Our research points the finger at poor survival overwinter and poor fledging as the probable demographic causes of population declines,” says Cox. “The next step is to figure out exactly what has changed in their environment and why these birds are dying during these critical life stages. We have additional work in progress that is aimed at answering these questions. When we know that, I hope we will be able to start making changes to improve survival and fledging.”

“It was an incredible opportunity to analyze a dataset that started before I was born,” adds Taylor. “Working with these long-term data had an emotional connection for me as a researcher and birder. My own fieldwork on Kent Island took place during the summers of 2014 and 2015, by which time most of the swallow nest boxes on the island were empty. For me, it was sobering to look back through the data and envision those nest boxes full of activity and life.”

“These studies are part of a growing number of studies addressing the causes of population declines among aerial insectivores,” according to the University of Wisconsin-Milwaukee’s Peter Dunn, a Tree Swallow expert who was not involved in either project. “In terms of understanding population declines in aerial insectivores, both studies point to adult survival during migration or on wintering areas as an important factor. Thus, these models identify areas where we can focus our future research efforts. Recent studies of Tree Swallow migration using geolocators suggest that populations breeding in eastern Canada are migrating along the east coast to winter primarily in Florida and Cuba, so these areas should probably be the next focus of study.”

Demographic drivers of collapse in an island population of Tree Swallows and Demographic drivers of local population decline in Tree Swallows (Tachycineta bicolor) in Ontario, Canada are available at http://americanornithologypubs.org/doi/full/10.1650/CONDOR-18-75.1 and http://americanornithologypubs.org/doi/full/10.1650/CONDOR-18-42.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology, published by the American Ornithological Society. For the past two years, The Condor has had the number one impact factor among 27 ornithology journals.

AUTHOR BLOG: Manage hunting and the rare can once again become the common

Wed, 10/17/2018 - 16:43

Lucía Vargas and Andrew Whitworth

Linked paper: Secondary forest is utilized by Great Curassows (Crax rubra) and Great Tinamous (Tinamus major) in the absence of hunting by A. Whitworth, C. Beirne, E. Flatt, R.P. Huarcaya, J.C.C. Diaz, A. Forsyth, P.K. Molnár, and J.S.V. Soto, The Condor: Ornithological Applications 120:4, November 2018.

Great Curassows and Great Tinamous are tropical gamebird species that are highly threatened by hunting and deforestation.

In one of the most biologically diverse rainforests of the world, the Osa Peninsula of Costa Rica, curassows and tinamous are thriving by hiding from hunters in protected, regenerating forests. These forests were once grasslands and disturbed forests that were hunted out. We have found that conservation efforts by the nonprofit group Osa Conservation (www.osaconservation.org) have been efficient for protecting these stunning gamebirds.

Game birds are important seed dispersers, control insect populations, and are food for many mid-level and apex predators. They provide social and economic services and are a source of protein, materials, and economic income from birding tourism. However, deforestation and hunting are leading causes of declines in populations of game birds such as the Great Curassow (Crax rubra) and the Great Tinamou (Tinamus major). The Great Curassow, for example, had lost 69% of its original habitat by 1977, and hunting was responsible for greatly reducing many populations, to the point of local extirpation in some regions. We wanted to know how valuable recovering habitats can be for such species, providing that hunted is controlled.

The field work to set up 60 camera traps during the very hot dry season was intense. It can be tricky to determine what factors play a role in habitat choice, but we had an ideal study site. Our grid covered a relatively small protected area (free from hunting) that comprises several different habitat types: old-growth primary forest, naturally regenerating secondary forest, recovering secondary plantation forests, and active agricultural land. Moreover, we analyzed the influence of roads, rivers, elevation, and whether cameras were located on or off trails, all of which are known to influence the distribution of rainforest wildlife.

Camera traps minimize researcher–bird contact and provide an effective means to study elusive ground-dwelling bird species. Here, Eleanor Flatt from Osa Conservation’s team, a co-author of the article, sets up a camera.

Both bird species chose to use secondary growth forest frequently, despite being described in other studies as primary forest specialist species. This is likely due to the eradication of hunting since the establishment of Osa Conservation in 2002, the close proximity of remaining old-growth forest tracts, and the fact that the regenerating forests have had over 45 years to recover.

One surprising result from our data was that Great Curassows are more likely to be seen near roads. This makes sense when we consider that they are likely benefitting from a higher abundance of fruiting trees, but they must be careful, because this could also result in what is known as an ecological trap. If hunting were to return, roads would provide easy access for hunters. On the other hand, although the tinamous utilized all types of forest, they very clearly avoided agricultural land. Even the forest strips in farm areas are not sufficiently safe and cozy for the Great Tinamou—they like it cool, dark, and well-connected.

Our study demonstrates the significance of protecting wildlife from hunting through understanding spatial behavior. What would the results be like at another site? In a place with no source population nearby to allow for natural recolonization as the forests recover, could we reintroduce and reestablish these species once hunting has been controlled?

Their importance as rainforest seed dispersers will affect the pathway of regeneration and growth of secondary forests, and their presence will also provide food for predators like ocelots and margays, assisting their recovery as well. “Secondary” forests don’t mean second-rate habitat—instead, they mean that wildlife and people have a second chance.

AUTHOR BLOG: A new hummingbird species in Ecuador

Wed, 09/26/2018 - 11:44

Elisa Bonaccorso

Linked paper: A striking, critically endangered, new species of hillstar (Trochilidae: Oreotrochilus) from the southwestern Andes of Ecuador by F. Sornoza-Molina, J.F. Freile, J. Nilsson, N. Krabbe, and E. Bonaccorso, The Auk: Ornithological Advances 135:4, October 2018.

Adult male (above left, center right), adult female (below), and immature male (above right) Oreotrochilus cyanolaemus. Image credit: P. Greenfield.

Last year a new hummingbird species was unexpectedly discovered on a seldom-visited mountain top in southern Ecuador. A brief visit to the rocky outcrops of Cerro de Arcos in the southern province of El Oro produced a photographic record that rang a bell: a mysterious immature male clearly assignable to the genus Oreotrochilus, the hillstars, which included six species at the time. A few days later, an adult male was captured in another photo, and a week after that, several males and females were observed and a handful collected for scientific purposes.

Such an outstanding discovery needed a thorough assessment to understand the taxonomic status and phylogenetic relationships of the putative new species and their evolutionary implications for the genus Oreotrochilus. This genus is remarkable in being the one that reaches the highest elevations: records above 4,500 meters, with a mean of 3,600 meters above sea level. As such, these hummingbirds need a very special set of physiological and behavioral adaptations to feed on the scarce nectar resources available. One plant in particular is extremely important for the hillstars—the spiny-leaved Chuquiragua, with its fire-orange flowers.

The newly discovered hillstar of southern Ecuador is not an exception in its feeding associations. In fact, its geographic range seems to be shaped by the availability of Chuquiragua in a very restricted region between the geographic ranges of the Ecuadorian Hillstar, Oreotrochilus chimborazo, found in Ecuador and extreme southern Colombia, and the Green-headed Hillstar, Oreotrochilus stolzmanni, found in Peru and extreme southern Ecuador.

The latter species is likely the closest relative to the new species, sharing an overall plumage pattern and being very similar genetically. But a single striking characteristic sets them apart: the Green-headed Hillstar has a glittering lime-green throat patch, or gorget, whereas the gorget in the new species is a glittering deep blue. Given that gorgets are likely used in courtship displays by males, the strikingly different color suggests that reproductive isolation is effectively segregating these taxa.

Being extremely restricted in distribution, confined to a few mountain tops where habitat degradation is dramatic, the conservation status of this new hillstar seems critical. No conservation projects exist across its tiny range; on the contrary, the agricultural boundary is progressing, cattle graze free in the few natural grasslands that remain, burns are frequent every windy summer, and not a few mining concession cover the area. Urgent research and conservation actions are on the way, but there is little time left.

Newly Discovered Hummingbird Species Already Critically Endangered

Wed, 09/26/2018 - 10:21

A male Blue-throated Hillstar. Photo credit: F. Sornoza-Molina

In 2017, researchers working in the Ecuadorian Andes stumbled across a previously unknown species of hummingbird—but as documented in a new study published in The Auk: Ornithological Advances, its small range, specialized habitat, and threats from human activity mean the newly described Blue-throated Hillstar is likely already critically endangered.

Hillstars are unusual among hummingbirds—they live in high-elevation habitats in the Andes and have special adaptations to cold temperatures. Francisco Sornoza-Molina of Ecuador’s Instituto Nacional de Biodiversida, first observed and photographed a previously unknown hillstar during fieldwork in southwest Ecuador in April 2017. After this first expedition, Sornoza-Molina engaged fellow researchers Juan Freile, Elisa Bonaccorso, Jonas Nilsson, and Niels Krabbe in the study of this possible new species, returning in May to capture specimens and confirm the finding. They dubbed the new species Oreotrochilus cyanolaemus, or the Blue-throated Hillstar, for its iridescent blue throat.

The Blue-throated Hillstar is found only along bush-lined creeks in an area of about 100 square kilometers, and the researchers estimate there are no more than 750 individuals, perhaps fewer than 500. Threats to its habitat include fire, grazing, and gold mining, and it meets the criteria to be considered critically endangered. “Complete support from national and international conservation agencies is needed in order to save this species,” says coauthor Francisco Sornoza-Molina. “The action plan for the conservation of this bird is creating a network of protected areas along its geographic range.”

“The hillstar hummingbirds occur in the most rugged, isolated, and inaccessible parts of the Andes, where they roost in caves, forage on the ground, and spend half their lives in hypothermic torpor, so the discovery of a new species in this group is incredibly exciting. This striking discovery confirms that life in the high Andes still holds many secrets to be revealed,” according to the University of New Mexico’s Christopher Witt, a hummingbird expert who wasn’t involved in the study. “The location is fitting for a new species of hillstar, because it’s a remote, high mountain range that is isolated and is sandwiched between the ranges of two other hillstar species. The authors did a thorough job comparing the new form to its relatives in every respect.”

A striking, critically endangered, new species of hillstar (Trochilidae: Oreotrochilus) from the southwestern Andes of Ecuador is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-18-58.1.

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.

Improving “Silvopastures” for Bird Conservation

Wed, 09/19/2018 - 10:34

Black-crowned Antshrikes are among the insectivorous birds that forage less efficiently in silvopasture habitat. Photo credit: B. Tarbox

The adoption of “silvopastures”—incorporating trees into pastureland—can provide habitat for forest bird species and improve connectivity in landscapes fragmented by agriculture. But how do silvopastures measure up to natural forest habitat? New research from The Condor: Ornithological Applications shows that birds in silvopasture forage less efficiently than those in forest fragments but offers suggestions for how silvopasture habitat could be improved.

The University of Florida’s Bryan Tarbox and his colleagues observed the foraging and flocking behavior of insect-eating birds in silvopastures on farms in the Colombian Andes between 2013 and 2015. They found that silvopastures were less structurally complex than forest fragments, with fewer and smaller trees, a sparser understory, and less diversity of tree species. Birds in silvopastures attacked insects less often, were less selective about where they foraged, and were less likely to join mixed-species flocks. Flock members attacked prey more frequently than solitary birds in forest fragments, but not in silvopastures, suggesting that something about silvopasture habitat negated the benefits of joining a flock.

The results show that silvopasture habitat could be improved by managing for higher tree species diversity and greater structural complexity, but that preserving natural forest fragments in agricultural landscapes is also crucial. “I hope people don’t get the impression that our results mean silvopastures aren’t a good idea,” says Tarbox. “The existing literature makes it clear that silvopastures are beneficial for biodiversity conservation. I think the big takeaway here is the importance of getting to the details of how specific land uses impact particular species or functional groups, so that we can figure out the best regional configurations of land use, given the competing needs of wildlife and agriculture.”

“Protected areas alone will be insufficient to conserve biodiversity at global scales. Instead, we must find ways to safeguard species and ecosystems while also sustaining human communities and livelihoods that depend upon local resources,” according to Cornell University’s Amanda Rodewald, an expert on bird responses to human land use who was not involved with the research. “In their study of insectivorous forest birds, Tarbox and his colleagues report that Andean silvopastures provided low quality foraging habitats and, as such, may fail to support resident and migratory birds as well as forest fragments. Fortunately, the study points to several strategies, such as planting preferred tree species and creating specialized microhabitats, that can be implemented at local and regional scales to improve suitability of silvopastoral habitats for birds.”

Foraging ecology and flocking behavior of insectivorous forest birds inform management of Andean silvopastures for conservation is available at http://americanornithologypubs.org/doi/full/10.1650/CONDOR-18-1.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology, published by the American Ornithological Society. For the past two years, The Condor has had the number one impact factor among 27 ornithology journals.

Newly Identified African Bird Species Already in Trouble

Wed, 09/19/2018 - 10:34

A Mountain Sooty Boubou. Photo credit: J. Engel

Central Africa’s Albertine Rift region is a biodiversity hotspot consisting of a system of highlands that spans six countries. Recent studies have shown that the population of sooty bush-shrikes occupying the region’s mid-elevation forests is a distinct species, and new research from The Condor: Ornithological Applications reveals that this newly discovered species may already be endangered due to pressure from agricultural development.

The newly identified mid-elevation species has been dubbed Willard’s Sooty Boubou, as opposed to the previously recognized high-elevation species, the Mountain Sooty Boubou. The Field Museum’s Fabio Berzaghi (now with the CEA Laboratory for Sciences of Climate and Environment in France) and his colleagues used museum records and bird survey records to analyze the ecological niche occupied by each species, and their results confirm that there is very little overlap between the ranges of the two species—Willard’s Sooty Boubou is found at approximately 1200–1900 meters and the Mountain Sooty Boubou at 1800–3800 meters. In Burundi, Rwanda, and Uganda, 70% of the potential for Willard’s Sooty Boubou lies outside of protected areas and has been converted to agriculture, and the numbers for the Democratic Republic of Congo are only slightly better.

Willard’s Sooty Boubou joins several other imperiled bird species that depend on the region’s mid-elevation forests, which have been largely overlooked by conservation efforts. “The Albertine Rift is a crossroads of amazing biodiversity, dramatic and diverse landscapes, and heartbreaking social and political unrest. It goes from glaciers to volcanoes to plateaus to lakes, with a succession of vegetation types from high-elevation cloud forests to lowland tropical forests,” says Berzaghi. “It is home to gorillas and forest elephants as well as a high number of endemic animal and plant species. Unfortunately, much of the region has gone through never-ending conflicts, with very negative consequences for both humans and biodiversity, and conservation involving local populations is paramount.”

“This paper provides additional data in support of the recognition of Willard’s Sooty Boubou as a species distinct from Mountain Sooty Boubou. Clarification of the niche that Willard’s Sooty Boubou occupies, that of mid-elevation forests, distinct from the higher-elevation Mountain Sooty Boubou, is important, because these habitats are among the most heavily impacted in Africa from agriculture,” according to UC Berkeley’s Rauri Bowie, an expert on African birds who was not involved in the study. “Conservation agencies have an opportunity to move beyond taxonomic debate and use the models derived from this species to improve conservation outcomes for not only this species, but also a broad set of mid-elevation Albertine Rift endemic vertebrates through protection of mid-elevation forests that have received relatively little protection in comparison to high-elevation montane habitats.”

Comparative niche modeling of two bush-shrikes (Laniarius) and the conservation of mid-elevation Afromontane forests of the Albertine Rift is available at http://americanornithologypubs.org/doi/full/10.1650/CONDOR-18-28.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology, published by the American Ornithological Society. For the past two years, The Condor has had the number one impact factor among 27 ornithology journals.

AUTHOR BLOG: “Bird-in-the-middle”—a mid-elevation tropical species stuck in limbo

Wed, 09/19/2018 - 10:34

Fabio Berzaghi & John Bates

Linked paper: Comparative niche modeling of two bush-shrikes (Laniarius) and the conservation of mid-elevation Afromontane forests of the Albertine Rift by F. Berzaghi, J.E. Engel, A.J. Plumptre, H. Mugabe, D. Kujirakwinja, S. Ayebare, and J.M. Bates, The Condor: Ornithological Applications 120:4, October 2018.

A search through the tropical forest literature for “mid-elevation forests” reveals relatively few results compared to a search for high-elevation or lowland forests, and looking at a map of protected areas and land cover in mountainous tropical regions makes it clear why. For example, in the African Albertine Rift, most national parks tend to be in high elevation areas where slopes are steep and land conversion for human use is more difficult. As we move down the slopes, the habitat starts degrading until we arrive in the lowlands, where almost no intact habitat remains, particularly on the eastern side of the Rift.

In 2010, Voelker et al. described a new species of bush-strike, the Willard’s Sooty Boubou (Laniarius willardi), and noticed that this species occurs at lower elevations than its sister species, the Mountain Sooty Boubou (Lanarius poensis). We were thus wondering how much habitat was left for this mid-elevation species, knowing that in this region lower-elevation forests are degraded or have been converted to agriculture. Using niche modeling and land cover data, we discovered that these two species of birds reside at different elevations across a small portion of montane Africa, overlapping only in part. Unfortunately, the habitat for L. willardi has been greatly reduced, because mid-elevation forests are outside protected areas and national parks. L. willardi may not be able to move to higher elevations, as its preferred environmental conditions are between 1200 and 1900 meters; a large portion of its suitable habitat is found in the Democratic Republic of the Congo’s Itombwe Plateau, technically a protected area but problematic to protect.

The plight of L. willardi is probably similar to that of many other mid- and low-elevation species in the area. Even though our results are not such good news for birds and other mid-elevation species in the region, we also want to highlight the importance of scientific collaborations with local researchers and conservation units. These collaborations help us define habitats and species in need of attention. Importantly, the authors of our study are a combination of Africans and non-Africans, with a range of research foci including ornithology and conservation but also niche modeling and bioinformatics. The data used in our study are based on both museum specimens (historical and modern) and modern field observations, which were carried out by teams that always included African students and scientists from the countries where the data were collected. Conservation can only be successful in the long run if in-country capacity for conservation science is developed around the world.

The discovery of L. willardi and its description were made possible through modern scientific collection during collaborations between local Albertine Rift ornithologists and the Field Museum. Data from such modern collections will help clarify lingering concerns in the taxonomic community (particularly Birdlife International and the IUCN) in regards to the status of these two species relative to other black boubous occurring far to the west in the Cameroonian Highlands. Work like this has great value, because it allows highlighting issues of conservation concern at both regional and local scales. Each region of the Albertine Rift has its own history and ongoing issues with deforestation, instability and protection. There is no “one size fits all” solution to conservation in the Albertine Rift, but this paper helps emphasize that there is regional expertise in the form of researchers and conservation professionals who will make a difference. Opportunities to work with international colleagues to combine conservation and science, as in this paper, will be instrumental in building efforts to protect the incredible biota of this wonderful region.

Mini Video Cameras Offer Peek at Hard-to-Observe Bird Behavior

Wed, 09/12/2018 - 09:56

 

Fledging behavior—when and why baby birds leave the nest—is something scientists know very little about. Rarely is someone watching a nest at just the right moment to see fledging happen. To get around this, the researchers behind a new study from The Auk: Ornithological Advances deployed miniature video cameras to monitor over 200 grassland bird nests in Alberta, North Dakota, Minnesota, and Wisconsin, and they found that fledglings’ decision-making process is more complex than anyone guessed.

Christine Ribic from the U.S. Geological Survey and her colleagues tested two competing hypotheses about fledglings’ decision making. Birds might leave the nest early in the day to maximize the amount of time they have to find a safe place to hide from predators before nightfall. Alternatively, once their siblings start to leave, the remaining birds might decide to stay in the nest longer to take advantage of reduced competition for the food their parents provide, resulting in spread-out fledging times. Video data analyzed by Ribic and her colleagues showed that the more siblings in a nest, the longer it took for all of them to fledge, consistent with the idea that some young may stay behind to take advantage of reduced competition after the first nestlings leave. Ribic and her co-authors discovered that 20% of nests took more than one day to completely finish fledging. Fledging behavior also varied between species and over the course of the breeding season, for reasons that remain unclear.

As they decide when to fledge, the nestlings of grassland birds are balancing two competing demands. On one hand, staying in the nest longer gives them more time to grow and develop before facing the risky outside world. On the other hand, predation risk might increase with time spent in the nest.

“It was exciting to see events naturally occurring in an area of avian biology where very little is known, and was only possible due to the use of video surveillance systems,” says Ribic. “It seems fledging is more complex than we previously thought. We were surprised by the span of time over which grassland bird species fledge, with some species starting to fledge in the early morning and others closer to noon, and by the frequency of fledgings that spanned multiple days.”

“Considerable research attention has focused on the breeding biology of birds, but until recently some events have been difficult to observe. Luckily, decreases in the size and cost of video equipment have allowed researchers to study these hard-to-observe events, such as the brief moments when a predator causes a nest to fail. This study took things a step further to begin exploring the point in time when young birds fledge from the nest,” adds the University of Illinois’s T.J. Benson, an expert of bird nesting behavior who was not involved in the study. “There are relatively few existing ideas for what influences the timing of nest departure by young birds, and Ribic and her colleagues put forth an interesting idea about the potential role of food availability in influencing fledging. Use of video technology to examine nest predation has become widespread, and this paper provides a great example of the other interesting aspects of breeding biology that can be examined in such studies.”

Diel fledging patterns among grassland passerines: Relative impacts of energetics and predation risk is available at http://www.americanornithologypubs.org/doi/full/10.1642/AUK-17-213.1.

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.

AUTHOR BLOG: What time do baby birds leave home?

Wed, 09/12/2018 - 09:56

Christine Ribic

Linked paper: Diel fledging patterns among grassland passerines: Relative impacts of energetics and predation risk by C.A. Ribic, C.S. Ng, N. Koper, K. Ellison, P.J. Pietz, and D.J. Rugg, The Condor: Ornithological Applications 120:4, October 2018.

A Grasshopper Sparrow chick leaves its nest. Credit: C. Ribic, USGS

We know that human kids grow, mature, and gradually move towards a life that is independent of their parents’ home.  The same is true for baby birds: they also have to decide when the time is right to leave the nest and start on their journey to independence. This seems to involve a balancing act between making sure they are big and healthy enough to survive independently, while leaving the nest quickly to avoid predators. Nests are busy places where chicks beg for food and parents are constantly coming and going with food deliveries. All of this activity could easily draw predators to the nest! The timing of chicks leaving the nest (fledging) isn’t well understood, particularly for birds that live in grasslands, many of which are threatened or endangered due to habitat loss.

Our new research focused on a variety of grassland songbirds, such as meadowlarks, sparrows, and longspurs. We found that the time baby birds leave the nest has more to do with having enough food (energetics) than avoiding predators. This is surprising because research on birds nesting in shrubs says that risk of predation is the most important thing affecting when chicks leave the nest. This suggests that nests in grasslands (hidden on the ground with protective cover from surrounding grasses and a few low shrubs) face different risks than nests placed in shrubs.

We found that grassland chicks can start to leave anytime throughout the day and when they leave depends on what species they are. Some chicks, like Clay-colored Sparrow and Grasshopper Sparrow, usually left the nest in the early morning, while Eastern Meadowlark and Chestnut-collared Longspur left closer to mid-morning. But sometimes chicks delayed leaving until the afternoon, with their siblings waiting until the next day to depart. The time it takes for all the chicks to leave a nest can be several hours to more than a day! Maybe some chicks are taking advantage of their siblings’ early departures to get more food and attention from mom and dad before they finally leave, too.

Measuring fledging time can be tricky because chicks run in and out of the nest multiple times before leaving for good. We don’t know why they do this; maybe they are exploring their world and gaining confidence before leaving to brave the world outside their home. Remember these birds have only been alive for a week and a half or so!  Regardless, it’s a bit like kids going off for college but returning for school breaks … nestlings may leave and return repeatedly before fully fledging. Fledging is not nearly as simple as people think it is!

Understanding the fledging process allows us to better understand the biology of grassland birds. Learning about the pressures they face in their daily lives lets us understand what threats they face and how those threats may change as people alter grasslands. Grassland birds are declining more than birds of any other habitat type across North America. Research like this is part of understanding why they are declining and what we can do to help them recover.

“Live Fast, Die Young” Lifestyle Reflected in Birds’ Feathers

Wed, 09/05/2018 - 13:53

A museum specimen ready to be photographed. Photo credit: R. Terrill

Animals’ lives tend to follow a quicker tempo as they get farther from the equator—birds at more northern latitudes mature faster, start reproducing younger, and live shorter lives, probably as a way of dealing with seasonal variation in resources. A new study from The Auk: Ornithological Advances shows for the first time that this pattern also plays out in birds’ feathers, with northern birds completing their annual molt faster to keep up with the demands of life far from the tropics.

Louisiana State University’s Ryan Terrill looked at museum specimens of four bird species with ranges that span a wide swath of latitude in both the Northern and Southern Hemispheres. Slight differences in feather growth between day and night during birds’ annual molt produce visible pairs of light-colored bars, each pair representing 24 hours’ growth. Terrill could determine the rates at which individual feathers grew by measuring their spacing. He found that for all four species, individuals collected at higher latitudes had grown their feathers faster.

Terrill sees two potential explanations for this pattern, which aren’t mutually exclusive. First, where the availability of food changes with the seasons, birds may need to molt faster so that they have the necessary resources. Second, because birds at higher latitudes tend to be more invested in producing offspring than in extending their own survival, faster production of lower-quality feathers may be an acceptable tradeoff.

“Working with museum specimens was a lot of fun,” says Terrill. “One of my favorite things about museum specimens is using them in ways that other folks might not consider, and especially using them in ways for which the original collector couldn’t have known they might be useful. It wasn’t until recently that many people considered that how feathers grow might be important for birds or realized that you could measure feather growth rates on specimens, and I hope this study will publicize yet another way that museum specimens are useful for understanding birds.”

“Most aspects of avian molt, with the exception of feather-replacement sequence, are thought to be rather flexible. The timing, location, and extent of molts appear to respond quickly to environmental constraints, even within populations of the same species occurring at different latitudes, as either permanent or winter residents,” adds the Institute for Bird Population’s Peter Pyle, an expert on bird molt patterns who was not involved with the study. “Yet molt strategies remain vastly understudied compared to other avian topics such as breeding, migration, and behavioral responses. This paper shows that a fourth component of molt, feather growth rate, also appears to vary, with equatorial populations showing slower molt intensity than those of higher latitudes. The author ties this nicely in to other studies suggesting a decelerated pace of other life history traits in less seasonal environments, perhaps as a function of slower basal metabolic rates.”

Feather growth rate increases with latitude in four species of widespread resident Neotropical birds is available at http://americanornithologypubs.org/doi/full/10.1642/AUK-17-176.1.

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.

AUTHOR BLOG: Count me in! I am available for detection at 6 AM on May 26th

Wed, 08/29/2018 - 15:08

Péter Sólymos

Linked paper: Evaluating time-removal models for estimating availability of boreal birds during point count surveys: Sample size requirements and model complexity by P.  Sólymos, S.M. Matsuoka, S.G. Cumming, D. Stralberg, P. Fontaine, F.K.A. Schmiegelow, S.J. Song, and E.M. Bayne, The Condor: Ornithological Applications 120:3, August 2018.

Point count survey duration rarely changes within projects but varies greatly among projects. As more and more large-scale studies are compiling and analyzing point count data from disparate sources, standardization becomes critical, because count duration greatly affects observations. The Boreal Avian Modelling (BAM, www.borealbirds.ca) project aims to further continental scale avian conservation through the integration and analysis of point count data collected across northern North America. In order to estimate population density and population size for landbird species, data integration became a real issue for us.

Two of the main sources of variation in the observed counts have nothing to do with ecological variables of interest, such as land cover and climate, but rather are considered nuisance variables. These are point count radius and point count duration. Recognizing that most studies do not follow survey protocol recommendations aimed to facilitate data integration (see e.g. Matsuoka et al. 2014), we opted to use model-based techniques to place our variable data on a common footing.

We first tackled standardizing for varying point count radii through distance sampling (Matsuoka et al. 2012) and eventually combined this with a removal model-based correction for varying point count duration. We named the method QPAD, referring to terms of our statistical notation: probability of detection (q), probability of availability (p), area surveyed (A) and population density (D) (Solymos et al. 2013). In the present paper we assessed different ways of controlling for point count duration. As the title indicates, we performed a cost-benefit analysis to make recommendations about when to use different types of the removal model.

We evaluated a conventional removal model and a finite mixture removal model, with and without covariates, for 152 bird species. We found that the probabilities of predicted availability under conventional and finite mixture models were very similar with respect to the range of probability values and the shape of the response curves to predictor variables. However, finite mixture models were better supported for the large majority of species. We also found overwhelming support for time-varying models irrespective of the parametrization.

So what is a finite mixture model? In our case, it splits the population of birds present at a location into frequent and infrequent singers. In previous parametrizations, researchers assumed that the singing rate of the infrequent group varies with date and time, whereas frequent singers remain frequent singers independent of time of year or time of day. We compared this to an alternate parametrization that assumes that individuals change behaviour over time and switch from frequent to infrequent singing behaviour—so it is the proportion of the two groups that varies. We found that the latter assumption was favoured.

Finite mixture models provide some really nice insight into how singing behaviour changes over time and, due to having more parameters, they provide a better fit and thus minimize bias in population size estimates. But all this improvement comes with a price: Sample size requirements (or more precisely, the number of detections required) are really high. To have all the benefits with reduced variance, one needs about 1000 non-zero observations to fit finite mixture models—20 times more than needed to reliably fit conventional removal models. This is much higher than previously suggested minimum sample sizes.

All of our findings indicate that lengthening the count duration from 3 minutes to 5-10 minutes is an important consideration when designing field surveys to increase the accuracy and precision of population estimates. Well-informed survey design, combined with various forms of removal sampling, is useful in accounting for availability bias in point counts, thereby improving population estimates and allowing for better integration of disparate studies at larger spatial scales. To this end, we provide our removal model estimates as part of the QPAD R package and the R functions required to fit all the above outlined removal models as part of the detect R package. We at the BAM project and our collaborators are already utilizing the removal model estimates to correct for availability bias in our continental and regional projects to inform better management and conservation of bird populations. Read more about these projects in our annual report.

A Better Way to Count Boreal Birds

Wed, 08/29/2018 - 15:08

Common Yellowthroats are among the birds for which new statistical models could provide better population estimates. Photo credit: C. Kolaczan

Knowing approximately how many individuals of a certain species are out there is important for bird conservation efforts, but raw data from bird surveys tends to underestimate bird abundance. The researchers behind a new paper from The Condor: Ornithological Applications tested a new statistical method to adjust for this and confirmed several mathematical tweaks that can produce better population estimates for species of conservation concern.

The University of Alberta’s Péter Sólymos and his colleagues tested a type of mathematical model called a “removal model” using bird count data for 152 species from the Boreal Avian Modelling Project, or BAM, which covers a vast area of Canada, Alaska, and the northeastern U.S. They found that incorporating variation in birds’ singing behavior improved models’ accuracy—how likely birds are to sing changes over the course of the day and the year, affecting how easy they are to detect. Extending the length of individual bird counts from three or five minutes to ten minutes was also beneficial.

“The chances of spotting something—a coin on the pavement, a bear in the mountains, or the apricot jam in the freezer—increases with effort,” explains Sólymos. “The more we walk, travel, look, or listen, the more things we find, but there is also a tradeoff between the number of places one can do a search and the length of the searches. Such decisions drive how long field biologists conduct bird counting at a given place. In our study, we looked at how the duration of counting influenced finding different bird species at different times of the day and the year. We also wanted to find the best way of how to standardize for different count durations and how to use these findings to provide better estimates of bird population sizes.”

This is more than just a math problem, however—accurate estimates of population size can be crucial for effective bird conservation, and many of the boreal bird species this study looked at are experiencing severe declines. This new approach offers a way to combine data from surveys that weren’t standardized in their design. “Population size of different species is one of the key metrics that affects their conservation importance, but estimating population size is a very challenging task that involves numerous assumptions,” says Sólymos. “Besides the ability to hopefully provide more accurate population size estimates, our modeling approach and findings can also help in timing of bird surveys to maximize the number of species detected.”

“While the authors of this study present the results of a rigorous comparison of modeling techniques to achieve better estimates of bird abundance from point counts, they also provide clear and simple recommendations on how and when to apply their findings to any study that expects to use time-interval point counts,” adds Jeff Wells, Science and Policy Director of the Boreal Songbird Initiative, who was not involved in the research. “This is a rich contribution not only to avian research methodology, but in the long run, also to bird conservation.”

Evaluating time-removal models for estimating availability of boreal birds during point count surveys: Sample size requirements and model complexity is available at http://www.bioone.org/doi/full/10.1650/CONDOR-18-32.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology, published by the American Ornithological Society. For the past two years, The Condor has had the number one impact factor among 27 ornithology journals.

How Does Agriculture Affect Vulnerable Insect-Eating Birds?

Wed, 08/29/2018 - 15:08

Tree Swallow with prey. Photo credit: C. Michelson

Aerial insectivores—birds that hunt for insect prey on the wing—are declining across North America as agricultural intensification leads to diminishing insect abundance and diversity in many areas. A new study from The Condor: Ornithological Applications looks at how Tree Swallows’ diets are affected by agriculture and finds that while birds living in cropland can still find their preferred prey, they may be working harder to get it.

The University of Saskatchewan’s Chantel Michelson, Robert Clark, and Christy Morrissey monitored Tree Swallow nest boxes at agricultural and grassland sites in 2012 and 2013, collecting blood samples from the birds to determine what they were eating via isotope ratios in their tissues. Tree Swallows usually prefer aquatic insects, which they capture in the air after they emerge from wetlands to complete their life cycles. The researchers suspected that birds living in crop-dominated areas would be forced to shift to eating more terrestrial insects, due to the effects of insecticide use and other agricultural practices on wetland habitat.

Instead, they found that swallows were eating more aquatic than terrestrial insects at all sites, and in 2012 it was actually the grassland birds whose diet contained a higher proportion of terrestrial insects. The results suggest that wetland habitat may provide a buffer against the negative effects of agriculture. However, birds living in cropland weighed less on average than their grassland-dwelling counterparts—a sign that they may be struggling.

“We set up this study to see if insectivorous swallows would be disadvantaged in agricultural croplands by shifting their normally aquatic diet to terrestrial insects to compensate for lower food availability. We were surprised that the birds did not generally do this,” says Morrissey. “Adult swallows in particular were heavily reliant on aquatic prey regardless of land use type. At the grassland dominated site, in fact, they fed their nestlings a wider variety of prey from both aquatic and terrestrial origin. Diet did not seem to influence body condition, but birds in cropland sites were lighter on average which may signal they are working harder in croplands to obtain their preferred aquatic prey. This work shows how important wetlands are for maintaining birds in agricultural landscapes and these are important reservoirs for conserving biodiversity in an otherwise heavily altered landscape.”

“Grasslands are one of the most imperiled ecosystems on the planet because their rich soils are ideal for agriculture. Pesticides and fertilizers are applied in ever-increasing quantities, which has serious implications for organisms that live there,” adds Acadia University’s Dave Shutler, an expert on Tree Swallow ecology who was not involved with the study. “This study compared the diets of Tree Swallows in natural grasslands and croplands, each of which had roughly similar wetland densities. Although diet composition was similar in both areas, it appears that diet quality was better in the natural grasslands, because birds there were heavier and in better condition than those in the cropland.”

Agricultural land cover does not affect diet of Tree Swallows in wetland dominated habitats is available at http://www.bioone.org/doi/full/10.1650/CONDOR-18-16.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology, published by the American Ornithological Society. For the past two years, The Condor has had the number one impact factor among 27 ornithology journals.

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