wildlife population demography in a changing world
A major focus of my research is understanding how global change impacts wildlife populations. To address this question, I combine intensive field sampling with quantitative demographic analyses.
My first postdoc on the oceanic island of Guam focused on the Såli (Micronesian Starling - Aplonis opaca), a songbird that is locally endangered due to the presence of the invasive brown treesnake (Boiga irregularis). I helped construct, deploy, and monitor snake-resistant nest boxes on Andersen Air Force Base in northern Guam to increase offspring survival. I monitored survival of radio-tagged birds across age classes (nestling, fledgling, juvenile, adult) to explore population demography. I also spearheaded and conducted an island-wide population census, which I compared with historical population datasets to investigate population trends over ~30 years. Banding efforts and population monitoring are ongoing (5 years and counting!) in collaboration with the U.S. Geological Survey and the U.S. Department of Agriculture. My second postdoc used one of the longest constant-effort mist-netting datasets in the Neotropics, to explore long-term population trends of birds over the past 45 years (1977-present) in Parque Nacional Soberania, a large (22,000 ha) protected area of intact lowland rainforest. We found widespread declines, with 70% of species (40 of 57) decreasing in abundance over the study period. Declines were largely independent of ecology (i.e., body mass, foraging guild, or initial abundance) or phylogenetic affiliation, and were also quite severe for many species, with 35 of the 40 declining species losing ≥ 50% of estimated abundance over the course of the study. Our findings indicate that protected areas may not be as sufficient for conserving tropical bird diversity as previously thought. I continue active collaborations in both systems, working to understand how intensified snake control efforts will impact Såli demography on Guam and focal species studies to drill down to the mechanisms of decline in Panama. |
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thermal physiology of endotherms
Understanding the influence of climate on species' thermoregulatory traits and capacity to tolerate rising global temperatures is another of my primary research foci.
To address this question, I use respirometry to measure organisms' oxygen consumption across a range of ambient temperatures to estimate estimate thermal physiological traits (e.g., basal metabolic rate, thermoneutral zone, heat tolerance). Understanding how these traits vary across species, space and time will be a critical first step towards predicting and mitigating future impacts of climate change. Related research projects include torpor in Neotropical hummingbirds and metabolic adaptations of Neotropical bats. |
species interactions - army ants and ant-following birds
While conducting my dissertation research in Panama, I became fascinated by an iconic species interaction of the Neotropics - army-ant (Eciton burchellii) swarms and the birds that follow them. I have investigated how Neotropical birds locate and recruit to army ant swarms - a profitable but patchy resource. I have used playbacks to simulate bird flocks foraging at ant swarms to understand how birds use social information (i.e. vocalizations of other species) to find swarms, whether this eavesdropping behavior is innate or learned, and how social information impacts flock structure. Finally, I have published a comprehensive review of army ant-following in Neotropical birds. My colleagues and I were recently awarded an NSF grant to experimentally investigate the impact of species loss on the structure and vulnerability of ant-following bird flocks to the breakdown of behavioral interactions. We are conducting a combination of innovative field experiments and detailed observations of bird species interactions and social behavior at ant swarms across the isthmus of Panama.
I am also starting comparative research in Africa in collaboration on the Afrotropical driver ants (Dorylus spp.) and the birds that follow them. My collaborators and I are interested in the role of driver ants, the lesser-known cousins of Neotropical army ants, as overlooked ecosystem engineers. Driver ants form the largest single-colony social insect societies in the world (>20 million workers) yet are far less studied than army ants. They also differ fundamentally from army ants in key aspects of their ecology, thus providin a natural point of comparison for understanding how swarm-raiding ants influence the ecology and evolution of their avian attendants. |
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human-wildlife interactions and urbanization
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My current postdoc research focuses on understanding the who, when, where, and why of human-bird interactions in urbanized landscapes. Who has access to birds, and are there differences based on sociodemographics or historical housing discrimination practices such as redlining? When during the year do people interact with birds, and when are different bird species present in a given location? Where is bird diversity higher - public parks or private yards? And where do people experience most of their interactions with birds in heterogeneous urban landscapes? Why do people connect with birds, and what bird functional traits drive both positive and negative perceptions by humans? I am working to address these questions in Champaign-Urbana, where we have put together a comprehensive bird database of the twin cities in both winter and summer and across public and private lands. Find out more about this research at our project website: https://human-bird-interactions.nres.illinois.edu!
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impact of invasive predators on prey behavior and ecosystem services
Following the introduction of the brown treesnake to Guam, most of the island's bird populations went extinct, including all but one of Guam's native frugivores - the Såli. As a result, frugivory and seed dispersal, an ecological process critical to ecosystem functioning, have been seriously impaired. To gain insight into how Guam's ecosystems might be put back together again, I have studied Såli diet, movement behavior, and roosting behavior to understand how they have persisted and whether they are still contributing to seed dispersal on Guam. Using fecal samples collected from nest boxes and mist-netted birds, I showed that the vast majority of the seeds in their diet came from native forest species. I also showed that they are dispersing seeds all over the urban landscape on Andersen Air Force Base in northern Guam, confirming their critical importance as the island's only remaining native seed disperser.
Current projects include (1) using radio-telemetry data collected during my postdoc to compare Såli movement behavior across age classes and between the populations on Guam (brown treesnake present) and the neighboring island of Saipan (snake absent) to tease apart how the snake has altered home-range size, roosting habitat use, and seed dispersal potential; (2) using roosting data from radio-tagged Såli to understand behavioral strategies for surviving predation at night, when nocturnal treesnakes are active; (3) a community-wide roost survey to understand how Guam's bird community as a whole is coping with the snake's nocturnal predation pressure. |
natural history
I believe passionately in the value of natural history as the foundation for asking the most compelling, informed biological questions. Natural history is especially relevant in the tropics, which are so diverse and yet still so poorly understood. I have helped compile species accounts of several tropical birds (Song Wren, Streak-chested Antpitta, White-bellied Antbird) for the Cornell Lab of Ornithology's Birds of the World. I am also co-editor of a natural history book, Elusive Birds of the Tropical Understory, focusing on the oft-underappreciated and rarely photographed birds of the dark understory of Neotropical forests.
I love coming up with creative natural history ideas from my own observations or from literature reviews. Some friends and I conducted a review of mammal hair-plucking behavior by birds, and we even invented an entirely new word for the behavior: kleptotrichy (Greek "klepto-" to steal + "trich-" hair)! I have also published several natural history notes, including brown treesnake consumption of fledgling birds on Guam and disturbance foraging associations between a Northern Tamandua anteater (Tamandua mexicana) and obligate ant-following birds. Current natural history projects include global reviews of disturbance foraging in birds and structural nest defenses in birds. |