Research Interests My research career began with my master's and Ph.D. theses on migratory songbird stopover biology in the New York metropolitan area. Upon returning home to New York City from college with a newfound interest in birds, it struck me that the city's parks (and those of many other cities) were regarded as premier birding destinations, but nobody knew if they were actually any good for the birds themselves. I figured that the very thing that makes many city parks great for birding in spring and fall (lots of migrants crammed into a small area) probably makes them terrible habitats for stopover refueling. My graduate research sought to better understand whether heavily disturbed forest fragments in urban landscapes can provide suitable stopover habitat for migrant songbirds. It turns out that they can. This work yielded the first or some of the first information on the refueling rates, body composition changes, movement patterns, and stopover durations of migrating birds in urban habitats, and is presented in six papers that can be accessed on the Publications page. Also check out my recent piece on the value of urban green spaces to migrating birds in Connecticut Audubon's State of the Birds report.
While working on urban stopover ecology, I developed a side-interest in the effects of mercury pollution on songbirds that, naturally, I quickly began thinking about in the context of migration. It was entirely unknown at the time how mercury exposure might impact the migration performance of birds and there was no talk of it to be found anywhere in the literature either. I have since written two commentary articles to bring attention to this issue and worked on several studies to determine how mercury affects songbird metabolism, endurance physiology, and behavior during this most challenging phase of the annual cycle. All of these papers can also be accessed on the Publications page.
My other research interests today range widely from the effects of non-native Japanese barberry on songbird habitat quality to the effects of light pollution on bats and the spatial ecology of wood turtles. The goal of all of my work is to better understand human impacts to wildlife and habitats through science that can help inform management decisions and public policy.
Effects of Japanese Barberry on Forest Invertebrates and Breeding Songbirds Japanese barberry has become one of the most widespread non-native, invasive plants in Northeastern forests, and yet little remains known about its effects on wildlife. In 2017, I began two parallel studies to investigate the physiological condition of ovenbirds breeding in Japanese barberry-invaded forest, and the biomass and community composition of their arthropod prey base. The first results from this work showed that branch-dwelling and leaf-litter arthropod communities in invaded areas are significantly different from and less species-rich than those where native vegetation is still dominant, although overall biomass does not differ. My paper on this study with co-author Robert Clark of Washington State University can be read here. Perhaps largely because the biomass of leaf-litter invertebrates (the main food source for ovenbirds) does not appear to be reduced in barberry-invaded habitats, there was no indication that the physiological condition of male ovenbirds depended on the density of barberry in their breeding territory. A paper on this study, coauthored with Susan Smith Pagano of Rochester Institute of Technology and Eric Slayton of Great Hollow, was recently published in Conservation Physiology and can be read here. With carbon and nitrogen isotope analysis, I am now investigating whether changes in arthropod community composition that are caused by barberry invasions in turn alter the diet composition of insectivores, again using the ovenbird as a model.
Host Plant Effects on Insect Nutritional Quality and Plant-Insect-Bird Trophic Interactions Plant species differ greatly in the abundance, richness, and diversity of insects they support, with non-native, invasive plants often representing the lowest-quality hosts. This can have cascading effects up the food web, beginning with insectivores, like birds. What is not well-understood, however, is how the quality of insects as food for birds might also vary across different species of host plants. Through a bird exclusion experiment involving 10 woodland plant species (6 native and 4 non-native), I and my Great Hollow colleagues, Dr. Robert Clark and Dr. Wales Carter, are currently investigating (1) prey selection of insectivorous birds across plant species, (2) differences in protein levels (as an index of nutritional quality) between the insect taxa eaten most and eaten least by birds, and (3) differences in insect protein content across host plant species. The results of this research are intended to help inform habitat management efforts that aim to benefit insectivorous birds by supporting intact, robust communities of insect prey.
Contrasting the Scale and Timing of Antioxidant-rich Fruit Consumption by Long- and Short-distance Fall-migrant Songbirds Along a Latitudinal Gradient Migration is a heavily taxing period in the lives of songbirds, and acquiring sufficient energy and nutrients en route is crucial for migration success. Although many songbirds rely on insects during the breeding season, they shift to fruits in the fall, which has been proposed to support their ability to complete migratory journeys by both reducing foraging costs and providing a source of antioxidants. High levels of antioxidant consumption could be particularly useful for aiding recovery after long flights or prophylactically preventing oxidative damage to muscle during flight. Similarly, starting to consume fruits earlier in the migratory season could prevent longer-term declines in condition, particularly for species with particularly long migrations. However, the timing of diet shifts by fall migrants, and the relationship between antioxidant consumption and energetic condition, have received little study. Great Hollow post-doc Wales Carter and I are using stable isotope analysis of feathers, red blood cells, and blood plasma to compare timelines of diet shifts between long- and short-distance congeners (Swainson’s thrush and hermit thrush), and using histological analysis of fecal samples to relate the degree of recent fruit consumption to energetic condition. This research is being conducted in collaboration with Dr. Susan Pagano of the Rochester Institute of Technology, using samples generously collected for us by the Braddock Bay Bird Observatory in New York and Powdermill Avian Research Center in Pennsylvania.
An Experimental Test of the Effects of LED Lighting on the Foraging Activity of a Connecticut Bat Community Mostly from research conducted in Europe, artificial lighting at night (ALAN) has been shown to be detrimental to some nocturnal bat species by displacing them from light-polluted areas while benefiting others that take advantage of the high densities of flying insects around light sources. The effects of ALAN on North American bats species are, by comparison, poorly understood. In collaboration with Dr. Amanda Adams at Texas A&M University, I conducted an experiment on the effects of LED lighting on bat activity at Great Hollow Nature Preserve. Using an experimental array of floodlights erected along the edge of our wetland and an acoustic bat recorder that detects the echolocation calls of bats, we have so far shown that LED light pollution significantly displaces some species, but not others, from illuminated areas. This results in a significant change in the species composition of the bat community. These findings were published in 2021 in the journal Ecology and Evolution and will help natural resources managers better evaluate potential impacts to bats from new development projects that involve nighttime lighting. We are now designing a follow-up experiment that will investigate the distances up to which LED lights have these negative effects on bats, so the full footprint of disturbance from light pollution can be better understood.
Spatial Behavior of the Imperiled Wood Turtle in Western Connecticut With my Great Hollow colleague, John Foley, Dr. Suzanne Macey of the American Museum of Natural History, and Columbia University graduate student, Jason Hagani, I have been working with a large, multi-year radio-telemetry data set to investigate the home-range sizes, movement patterns, and site fidelity of wood turtles in a part of the range where these aspects of their ecology have not been previously studied. Plans for long-term monitoring will also provide the data needed to determine survivorship of this population in the face of threats from vehicles, water pollution, and an abundance of synanthropic predators like raccoons. A recent publication on this work can be accessed here.
Metabolic Effects of Methylmercury Exposure in Spring-migrant Yellow-rumped Warblers: Implications for Migratory Performance Migratory birds are able to fuel long-distance flight with extramuscular fatty acids by seasonally upregulating catabolic enzymes and transport proteins that greatly increase the rate at which fatty acids can be mobilized, delivered to working muscles, and oxidized. There is concern that the broad tendencies of the toxin methylmercury (MeHg) to inactivate enzymes and limit the function of other proteins in vertebrates could compromise these important processes underlying endurance flight, but this has yet to be investigated. In collaboration with Drs. Christopher Guglielmo, Yanju Ma, and Brian Branfireun of the University of Western Ontario, and Dr. Alex Gerson, Dr. Derrick Groom, Cory Elowe, and Mustafa Yildirim of UMass-Amherst, I am investigating the effects of short-term MeHg exposure on the pectoralis and liver catabolic enzyme activity, FA transporter expression, and peroxisome proliferator-activated receptor (PPAR) expression of yellow-rumped warblers to determine whether mercury pollution may be compromising the long-distance flight abilities of migratory birds.
Birds as a Potential Dispersal Mechanism of the Asian Long-Horned Tick in Eastern North America The Asian long-horned tick was first discovered in the U.S. in 2017 and has now been documented in at least 8 states. In its native range in Asia, the tick is a vector of hemorrhagic fever and Japanese spotted fever in humans, and is a devastating pest of livestock. It is currently unknown what threat the Asian long-horned tick presents to people, domestic animals, or wildlife in the U.S., or how far and fast it will spread. Its rapid spread through the eastern U.S. so far, however, indicates that migratory birds might be a primary mechanism by which the Asian long-horned tick is moved around. Birds are a common host of Asian long-horned ticks in Asia, but it is unknown whether any North American bird species represent suitable hosts. I am currently working with Dr. Neeta Connally of Western Connecticut State University to survey free-living birds at invaded and non-invaded sites in CT to investigate whether birds carry Asian long-horned ticks, and if so, what species of birds and birds associated with what habitat types. We are also working to develop a behavioral assay to test the relative attractiveness of feathers from various eastern North American birds to lab-reared Asian long-horned ticks.
Population Monitoring of the New England Cottontail at Great Hollow Nature Preserve The rare and declining New England cottontail is the only native rabbit species of the Northeast. Not to be confused with the introduced eastern cottontail that is ubiquitous to suburban backyards and the like, the New England cottontail is currently known to occur in only 104 sites across its geographic range, from southern New York and Connecticut to Maine. Nearly identical, the two species can only be reliably distinguished from one another molecularly. Working with the Connecticut Department of Energy and Environmental Protection (DEEP) to collect and analyze fecal pellets, I and my Great Hollow colleague, John Foley, have confirmed the presence of New England cottontails on our preserve. We are one of only 58 sites in the state of Connecticut in which the species is known to occur. Now, we are working with the University of New Hampshire to genotype the DNA extracted from the fecal pellets in order to distinguish different individual rabbits from one another and estimate the size of the New England cottontail population at Great Hollow. We’re also exploring opportunities to study the rabbits in more detail and manage areas of the preserve to enhance habitat conditions for New England cottontails while discouraging their invasive competitor, the eastern cottontail.