Homebody Tendencies Put Hawaiian Gallinules at Risk

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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

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.

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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.

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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

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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

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.

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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.

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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.

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AOS welcomes new Communications Specialist

Rebecca_Heisman_03 - CopyAOS is excited to welcome Rebecca Heisman as our new Communications Specialist! Rebecca will be working part time through the end of the year and joining AOS as our first full-time communications staff member in January 2019. Among other duties, Rebecca will be taking the reins of AOS’s Twitter account, Facebook page, and website.

Rebecca spent the past four years as a freelance writer and science communicator (with The Auk and The Condor among her clients). Prior to that, she earned a master’s degree in natural resources and was a field technician for bird research projects in Canada and Australia.

Rebecca is looking forward to finding new ways that AOS’s various communications channels can serve the society’s members. If you have any ideas to share about this, she’d love to hear from you! You can contact her at rheisman@americanornithology.org.