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Avian diversity
in the
Southeastern Peruvian Andes
Collaborators: Chris Merkord A primary goal of my research is to understand the spatial patterns of species diversity in tropical Andean landscapes. Within the Manu Biosphere Reserve, our research team has used auditory-visual counts and mist nets to survey an expansive elevational gradient of 2600 meters, ranging from foothill forests at 800 meters (2,625 feet) to forest treeline at 3400 meters (11,150 feet). I am now using these census data to quantify and describe patterns of avian richness and species turnover with elevation, and to assess the degree to which landscape heterogeneity found at similar elevations, generated by variation in topographic complexity and recovery from landslide disturbances, contribute to the overall diversity of bird faunas. This aspect of species turnover has been largely ignored in previous studies of elevational gradients, perhaps due to sampling limitations in difficult terrain, but it is nevertheless important for understanding levels of patchiness and habitat specialization of species within their ranges. These data serve multiple purposes for other research projects, for example, serving as training and test data for species distribution models, including those that utilize remote sensing data, for modeling species' response curves along elevational gradients, and for comparisons with diversity patterns of other taxonomic groups. My collaborator, Chris Merkord, maintains the Kosnipata Ecosystem Project website, which describes some of this work and other ongoing projects in the Manu Biosphere Reserve. |
 Cloud forest after a mid-afternoon rainstorm in Manu at 1700 m. |
 Eutoxeres condamini is found in the lower elevations of Manu National Park. We might expect this species to be specialized to few flowering plant genera based on its bill morphology. Photo by Zach Peterson. |
Hummingbird
Specialization to
Flowering Plants in the Andes
The
highest diversity of hummingbirds is found in the Andes Mountains in
South America,
where species often have elevational distributions of a few hundred
meters. Despite their well-studied specialization to flowering-plants,
no one has examined how relationships between hummingbirds and
flowering plants may constrain hummingbird species’ elevational
distributions. One enormous advantage of hummingbirds
is that they leave a record of which flowers they have visited through
the accumulation of pollen on their bills and heads, thus making costly
studies that follow hummingbirds as they move through the environment
unnecessary. In our project, we used the Neotropical Pollen
Database develolped by the Palynology lab of Mark Bush to identify
pollen samples
collected from bills of captured hummingbirds along an elevational
gradient in Manu, and we are now compiling a list of flowering plants
visited by each
of 38 species of hummingbirds. These data, combined with data on the
occurrence of those hummingbird and
flowering-plant species along the same gradient, will be used to
determine whether range limits in hummingbirds specialized to few
flowering-plant species coincide with limits in the distribution of
their flowering plants, whether hummingbirds with broad distributions
change their use of flowering-plant resources with elevation, and
whether specialist hummingbirds are constrained to narrower elevational
ranges compared to generalists.Collaborators: Mark Bush, Doug Levey, Scott Robinson, Honey Whitney |
 To
collect pollen we rub a small slice of prepared gelatin over the
hummingbird's bill and forehead. This gelatin is then melted and fixed
on a microscope slide under a glass coverslip. Photo of Ocreatus
underwoodi by Zach Peterson.
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Andean
bird-vegetation associations: using
remotely
sensed RADAR data for distribution
modeling
and biodiversity mapping
Collaborators: Chris Merkord, Norma Salinas, Sassan Saatchi, Miles Silman, Mark Williams The study of biodiversity in tropical montane forests has long been plagued by an inability to access and sufficiently sample the heterogeneity of these complex landscapes. Birds are among the most well studied taxa, yet even the most detailed studies of avian distributions in tropical mountains describe elevational ranges by limits of occurrence along single transects, or estimated abundance based on limited spatial sampling. For birds, we know that vegetation structure and complexity is an important predictor of species richness and is used in habitat selection for individual species, but ground-based vegetation sampling is time-consuming, spatially limited, and sometimes down right dangerous in steep mountainous terrain. Advances in active remote sensing now allow detailed, quantitative measures of vegetation to be gathered over thousands of square kilometers. This could be enormously useful for understanding patterns of avian diversity and distributions. This project will combine our data of tropical bird abundances along the elevational gradient in Manu with interferometric Synthetic Aperture Radar (inSAR) data for the entire study area. Using variables derived from radar data as indicators of vegetation structure (e.g., canopy height, above-ground biomass), we can generate landscape-scale predictions for bird species richness, variation in species composition (beta diversity), and individual species’ distributions for this Andean landscape, including population size estimates for the best modeled species. Remote sensing and GIS applications will be used to construct maps of spatial patterns of avian diversity for the montane regions of Manu National Park. |
 Overview of Departments of Cusco and Madre de Dios, Peru. Yellow and blue swaths indicate flight paths for remotely sensed radar data. The yellow swaths, collected in July 2009 by Earth Data, Inc., cover the montane portion of the Manu region. |
| Understanding
evolutionary relationships of Andean
birds through ectoparasitic chewing lice Collaborators: Julie Allen, Kevin Johnson, Gustavo Londono, Jessica Oswald, David Reed, Aaron Savit, Judit Ungvari-Martin, Jason Weckstein An
assortment of ectoparasites live on birds, among which are chewing lice
specialized to the wing feathers and body. These parasites often
track the evolutionary histories of their hosts, though this occurs in
differing degrees of cospeciation. Such relationships give us the
opportunity to study microevolutionary processes in bird hosts at regional spatial scales, such as dispersal, gene flow, and
population divergence, as well as macroevolutionary patterns
of host-parasite coevolution in species groups distributed across
biogeographic provinces. As part of
our research efforts in Manu, we have collected ectoparasites from
captured birds using a feather dusting technique. With these
data, we are now joining forces with bird lice experts and collections
in the Field Museum of Chicago to investigate micro- and
macroevolutionary patterns in Amazonian and Andean birds.
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 This
Crowned Chat-Tyrant (Ochthoeca spodionota) was feeding nestlings near
treeline at 3400 meters. Perhaps due to this constraint, she didn't
have time to preen feathers, leaving them susceptible to chewing lice.
The barbs on her chest contour feathers have been completely
eaten, leaving only the rachii.
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 Cloud
forest habitats are moisture-saturated, resulting in moss-laden tree
trunks and unmatched epiphyte diversity and abundance. Our study
shows that range boundaries of numerous bird species coincide with the
lower limit of cloud forest along the steep biophysical gradients of
the Pacific slope.
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Endemism,
beta-diversity, and consequences of
climate change in Central American cloud forests
Collaborators: Anna Ciecka, Matthew Gasner, William Haber, Keiller Kyle, Robert Lawton, Kerry Rabenold The leeward Pacific slope of the Tilaran Mountains offers a unique opportunity to examine the effect of steep biophysical gradients on the organization of biodiversity. A central feature of this gradient is the "cloud forest margin" which is characterized by major shifts in vegetation structure and punctuated species turnover. This mountain range also exhibits extraordinarily high levels of endemism, harboring numerous species limited to Central America and an even greater proportion of species limited to the Costa Rican - Panamanian highlands. The combination of climate warming and regional deforestation are expected to generate serious warming and drying effects on the cloud forests of this region, adding to the need for urgent and precisely placed conservation efforts. Our research of the bird and tree communities of this landscape spans a decade, in which time we have quantified the diversity of avian and tree communities and the correlative effects of temperature and moisture on species composition along the gradient. We have found that many narrowly endemic birds tend to be numerically rare, in addition to being habitat specialists, creating a "syndrome of rarity" for many cloud forest inhabitants. Our yearly censusing of the bird community now allows us to assess yearly variation in abundances of cloud forest species and to provide critical data for analysis of population viability for endemic species. |
 This Gray-breasted Wood-Wren (Henicorhina leucophrys) replaces the White-breasted Wood-Wren (H. leucosticta) in the Tilaran mountains of Costa Rica. Photo by Rosalbina Butron. |
Elevational
species
replacements: Testing the
Interspecific Competition
Hypothesis in Neotropical Birds
The phenomenon of elevational replacements between closely related species is well documented in tropical birds, especially in the Neotropics. It is assumed that interspecific competitive interactions underlie these replacements, preventing the coexistence of strong competitors. In his study of the Vilcabamba elevational gradient, Terborgh (1975) concluded that such competitive interactions could limit the elevational ranges for up to 30% of the montane species detected. These conclusions were based primarily on distribution patterns of congeners along single gradients, as well as evidence for range expansion along mountain slopes where one species of the congener pair was absent. Until now, experimental evidence to support the interspecific competition hypothesis in tropical mountains has been lacking. My project used interspecific playback experiments to test for territorial behaviors between species in their contact areas along elevational gradients. Such aggressive territorial interactions between species, if detected, would support the hypothesis that interspecific competition maintains these range boundaries in montane species exhibiting elevational replacements. Using recorded songs of target species, I conducted a series of these playbacks (control, congener, and conspecific) to birds holding territories in replacement zones between congeners, and at increasing distances moving away from these zones, where interspecific encounter rates decline precipitously. I have conducted these playback experiments in both the Tilaran Mountains, Costa Rica, and in Manu National Park, Peru. Results from the Tilaran mountains of Costa Rica show that species respond aggressively to congener songs in playback experiments where species come into contact along the gradient. As one moves away from the replacement zone, however, responses to congener songs grow weaker, and at distances well within the elevational ranges of these species, responses to congener songs cannot be distinguished from responses to negative control playbacks. While species tested in Costa Rica showed aggressive interactions with congeners at range boundaries, the strength of interspecific aggression varied between species and among genera, suggesting that some species could be behaviorally dominant. We emphasize that interspecific aggressive interactions at range boundaries, and especially asymmetries in interactions could pose constraints on species as they attempt to shift along with changing regional climate regimes. |
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| Using phylogenetic approaches to
understand suboscine diversity and diversification in
heterogeneous
Amazon forests Collaborators: Julie Allen, Jessica Oswald, Judit Ungvari-Martin, J. Gordon Burleigh |
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| Resilience
of
spruce-fir bird communities to invasion of the exotic Balsam Woolly
Adelgid Collaborators: Anna Ciecka, Kerry Rabenold |
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 A
nesting Northern Mockingbird (Mimus polyglottos) attacking a "repeat
offender" threatening its nest. Photo by Aaron Spalding.
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Mockingbirds
quickly learn to recognize individual humans
Participants: Monique Hiersoux, Doug Levey, Gustavo Londono, John Poulsen, Scott Robinson, Christine Stracey, Judit Ungvari-Martin After working with Northern Mockingbirds for several months, my lab mates, Gustavo Londono and Christine Stracey, began to talk about their mockingbirds becoming more and more aggressive toward them, as they returned periodically to monitor the nests they found. What's more is they were not acting more aggressively toward other passersby--this seemed to be directed at them. One day, Gustavo happened to walk by a nest he was monitoring on campus, when one of the mockingbirds picked him out of a crowd of ordinary college students on the sidewalk and dive-bombed at his head, to the shock of the many bystanders! These observations spurred our graduate and undergraduate research groups in the Robinson and Levey labs to organize a formal investigation of mockingbirds' ability to recognize us as individual humans. Our study, published last year in Proceedings of the National Academy of Sciences USA, received nationwide press coverage. The take home message is that mockingbirds have a spectacular ability to remember threats to their nests, much more than we have given them credit for! Check out this example of recognition ability by mockingbirds, and see if you can tell which person is the most threatening to this pair of birds! And here are links to articles in the press that covered our study: ScienceNOW, Telegraph.co.uk, CBS News |
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Ecological
pressures
shaping bird song characteristics
Another ongoing project focuses on the
effects of urban noise on bird song characteristics. Several
studies have now shown that birds can adapt several aspects of their
songs in order to transmit a better signal in noisy environments.
In urban areas, birds may sing louder (increasing amplitude) to
overcome increased ambient noise, sing at different times of day, or
even change the pitch (or frequency) of the songs that they sing.
It is this final characteristic that we have studied in the
Northern Mockingbird. Two undergraduate students, Puja Patel and
Michele Feole, have dedicated many hours to collecting field recordings
of singing mockingbirds in and around Gainesville, spanning noise
environments that range from bustling rush-hour traffic at major urban
intersections to quiet pastures in the countryside. So far we
have found that mockingbirds in urban areas indeed sing at a higher
pitch, adjusting the minimum frequencies of their songs to avoid
competing with the low frequency rumble of urban road noise.
Non-urban mockingbirds, by comparison, maintain their songs at
lower frequencies, which can transmit easily through a less noisy
environment. This project continues to offer multiple
layers of interesting questions because of the complicated singing
behaviors of mockingbirds to mimic birds in their environment.
Find out more on our work with mockingbird song along an
urbanization
noise gradient here.Collaborators: Michele Feole, Doug Levey, Puja Patel, Marcela Salazar, Christine Stracey |
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