Current Projects


Biological research is at the core of what we do at Great Hollow. Our researchers and collaborators conduct conservation-driven studies of biodiversity in Connecticut and beyond to better understand human impacts to the environment and provide science that can help guide management decisions and public policy. We specialize in integrating the fields of animal ecology, physiology, and toxicology to investigate the effects of introduced species, land use change, and pollution on wildlife and habitats.  We take a highly collaborative approach to research, pooling and leveraging the skills and resources of multiple partners across academia, government, and non-governmental organizations to most effectively and efficiently approach scientific studies of common interest. Below are some of the projects we are currently working on.

Effects of Japanese Barberry on Forest Songbird Breeding Habitat Quality

Since its introduction from Asia in the late 1800s, Japanese barberry has become one of the most widespread non-native invasive plants in Northeastern forests, and like most other non-native invasive plants, is assumed to diminish habitat quality for forest wildlife. Yet, surprisingly few studies have actually investigated the effects of Japanese barberry on the wildlife that inhabits invaded areas. Great Hollow is conducting an integrative assessment of the effects of Japanese barberry on breeding habitat quality for forest songbirds, using the ovenbird as a model. The first stage of this research examined food abundance and the physiological condition of ovenbirds in breeding territories with either extensive or little to no Japanese barberry coverage, and was published in 2019 in Conservation Physiology. We are now investigating differences in their diet composition between highly or minimally invaded areas of forest, using carbon and nitrogen isotope analysis.  The goal of this research is to allow for more science-based decision making among land managers and conservation practitioners who are grappling with Japanese barberry invasions across the Northeast.

Effects of Japanese Barberry on Invertebrate Food Webs

The effects that non-native plants have on the abundance and diversity of foliage-dwelling and leaf litter invertebrates in forests are poorly understood. Invertebrates play an important role in forest nutrient cycling and are a critical food source for birds and other wildlife higher up in the food web. Working with Dr. Robert Clark at Washington State University, we conducted a study to compare invertebrate biomass, diversity, and community composition on Japanese barberry to that of native plants in the forest understory and leaf litter. We found 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. The study was recently published in Environmental Entomology and can be read here. We are now investigating whether these differences in arthropod community composition driven by barberry invasions alter the diet composition of woodland insectivores, using the ovenbird as a model. We are also planning to compare the quality of arthropods as prey for insectivores, including macronutrient composition, antioxidant content, and polyunsaturated fatty acid content, between barberry-invaded and barberry-free areas of forest.

Impacts of Light Pollution on the Foraging Activity of Bats

Populations of many bat species are in dramatic decline due to the outbreak of a disease known as White-nose Syndrome. Bats are also facing a series of other threats from habitat loss, wind turbine collisions, chemical pollution, and light pollution. As nocturnal animals, bats may be adversely affected by the abundance of artificial lighting in our cities and towns, along our roads, and around our homes, but this has not been well-studied in North America. In collaboration with Dr. Amanda Adams of Bat Conservation International and Texas A&M University, Great Hollow is studying the effects of L.E.D. lighting on bat activity at our preserve. Using an array of lights erected along the edge of the wetland at the southern end of the preserve and an acoustic bat recorder that detects the echolocation calls of bats and identifies them to species, we are able to compare bat activity levels on nights with and without the lights turned on. The findings of this experiment will help natural resources managers to evaluate potential impacts to bats from new development projects that involve nighttime lighting. Read an article on our research in the newsletter of the American Wildlife Conservation Foundation here.

Home Ranges and Movement Patterns of Wood Turtles

Great Hollow’s naturalist, John Foley has been consistently radio-tracking wood turtles at various sites in Fairfield County, CT and Putnam County, NY for the past several years. In collaboration with Dr. Suzanne Macey at the American Museum of Natural History and Columbia University undergraduate student, Jason Hagani, we are using these data to determine the home range sizes and area requirements of male and female wood turtles in our region, and examine annual fidelity to their hibernacula and core breeding season habitats. Continued monitoring of these turtles will also provide long-term data needed to determine their survivorship in the face of threats from vehicles, water pollution, and an abundance of synanthropic predators like raccoons. Check out a recent conference poster of the project’s findings here.

Effects of Mercury Pollution on the Migratory Behaviors of Songbirds

Mercury is a global pollutant and a powerful neurotoxin that has become increasingly widespread in the environment as a result of a two- to three-fold increase in atmospheric emissions over the past 200 years. The threats of mercury pollution to fish-eating wildlife and other top predators have been well-documented, but it has recently become apparent that animals at lower positions in food webs, like songbirds, can also accumulate harmful levels of mercury. However, it is largely unknown at what level mercury begins to cause adverse effects in songbird species. We also know next to nothing about how mercury exposure might affect the ability of birds to migrate long distances. In collaboration with Drs. Chris Guglielmo, Yolanda Morbey, and Yanju Ma at the University of Western Ontario, Great Hollow scientists radio-tagged and tracked (see yellow-rumped warblers of differing blood mercury levels during their spring migration to investigate the effect of mercury on migration behavior and orientation. The study was recently published in the Journal of Ornithology and represents the first study of the effects of mercury pollution on the migratory behavior of birds. In the second phase of this work, we are now investigating the effects of mercury on the endurance physiology 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

The Asian long-horned tick is an invasive species that was first discovered in the U.S. in 2017 and has now been documented in at least 8 states, including Connecticut and New York. 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 North American bird species represent suitable hosts. In collaboration with Dr. Neeta Connally at Western Connecticut State University, Great Hollow is surveying various species of migratory and resident birds at our nature preserve for the presence of ticks during spring migration and the summer breeding season to investigate whether birds carry Asian long-horned ticks, and if so, what species of birds and birds associated with what habitat types are the most common hosts. Preliminary findings of this work were presented at the 2020 conference of the Entomological Society of America and can be viewed here. Great Hollow also works with Dr. Connally to monitor temporal trends in the abundance of black-legged ticks (the vector of Lyme disease) in western Connecticut.

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 northeastern United States. Not to be confused with the introduced and invasive 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 by DNA. For the past three winters, the Connecticut Department of Energy and Environmental Protection (DEEP) and Great Hollow researchers have been conducting standardized transect surveys of our preserve to collect fecal pellets for genetic analyses, and have confirmed the presence of New England cottontails. Great Hollow Nature Preserve is 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 that area of our preserve to enhance habitat conditions for New England cottontails while discouraging their invasive competitor, the eastern cottontail. Stay tuned for more!

Additional Projects

In addition to the above projects that are being lead by Great Hollow, our staff also frequently collects data for, or otherwise supports projects that are lead by researchers at other institutions. Such projects to which Great Hollow is currently contributing include:

Black Bear Distribution and Land-cover Associations in the Lower Hudson Valley (Project Lead: Budd Veverka, Mianus River Gorge)

Black-legged Tick Population Monitoring in Western Connecticut (Project Lead: Dr. Neeta Connally, Western Connecticut State University Tick Lab)

Connecticut Bird Atlas Project (Project Leads: Dr. Chis Elphick, UConn and Dr. Min Huang, CT Department of Energy & Environmental Conservation)

Motus Wildlife Tracking System

Past Projects

Please visit our Publications page to see the results of all of our previous research projects.