Documenting the decline of North American birds

The abundance of North American birds have declined ~29% since 1970. Current abundance monitoring approaches primarily involve standardized surveys. While informative, these surveys provide limited information about species declines and the underlying causes of these declines. To help fill this gap, I created the largest existing repository of North American bird mortalities over the past century. By doing so, I aim to empirically validate one of the world’s more prominent citizen scientist approaches (e.g., documenting wildlife mortalities), describe main causes of declines of North American bird species, and demonstrate that documented mortalities are a robust proxy for abundance change. More about this project soon.

Rapid consumer evolution following predator mortality events

Predator declines are emblematic of the Anthropocene. These declines have been increasingly exacerbated by mass mortality events, or sudden die-offs. To understand how consumer life history traits may change following these biological catastrophes, I conducted a rapid evolution experiment with Daphnia, a model organism for aquatic food webs. Specifically, I exposed individuals to different levels of two key features of predator mortality events: different predator regimes (i.e., the death of predators, and thus different types of consumptive effects) and different resource levels (i.e., the decomposition of predators, and thus different resource levels. More about this project soon.

Mass mortality events of lentic fishes

Over the past century, mass mortality events of freshwater fish have increased in frequency and intensity. These catastrophes are often caused by direct and indirect effects of temperature, such as direct thermal stress and low dissolved oxygen concentrations, respectively. I compiled one of the most comprehensive databases of fish mortalities across north temperate lakes of North America, thermal tolerances of affected taxa, and concurrent temperature estimates. I then used future temperature projections to predict the frequency of fish mortalities due to warm temperatures (i.e., summerkills) over the 21st century. Our findings were featured on NPR’s Science Friday and Minnesota’s NPR.

Ecological dynamics of
mass mortality events

Mass mortality events of predators have increased in frequency and intensity for most major animal groups, particularly aquatic animals. Some long-term ecological implications of these events, such as defamation and trophic downgrading, are well understood. However, limited information is available about short-term ecological implications of these biological catastrophes. We experimentally tested recent theory that surmised predator mass mortality events combine aspects of predator removals and resource pulses in tai-trophic food webs. To test this idea, I constructed mesocosms with tri-trophic freshwater food webs (phytoplankton, zooplankton, and fish), induced the defining characteristics of these disturbances, and intensively compared ecological dynamics. More about this project soon.

Damselfly digestive physiology

Organisms often exhibit tradeoffs between physiological attributes to accommodate for various ecological and environmental factors. To understand whether these tradeoffs exist at the species- or population-level, we conducted growth trials with 120 vesper bluet damselfly larvae (Enallagma vesperum) from lakes with contrasting population densities. Before growth trials began, we induced varying levels of melanization, a generalized immune response for invertebrates, by penetrating the exoskeleton (lower middle) or implanting a microfilament (lower right). Preliminary results suggest that significant infraspecific variation obscures potential tradeoffs between digestive physiology and melanization, and 2) tradeoffs vary among populations. Top photo by Stephen R. Krotzer.

Natural flow regime of the Gila River, New Mexico

The upper Gila River is one of few major waterways in the southwestern United States that retains a nearly natural flow regime. Dr. Mary Harner, Emma Brinley Buckley, and I examined aerial and satellite imagery (1935-2016) to quantify temporal change in floodplain habitat and channels of this dynamic river. Due to dwindling freshwater resources in the southwestern United States, a diversion was proposed along this particular river segment as part of the 2004 Arizona Water Settlements Act. This ongoing project aims to document changes over the past century and the current state of the river. Concurrently with this project, Dr. Harner produced a documentary, Life on the Gila, that discusses the future of this majestic river by way of farmers, ranchers, and local residents. Active channels were extracted from NMED, USDA and USGS aerial and satellite imagery. Background image is a modified USGS satellite image from 2016.

Sopris, Colorado

My grandfather, Alfred Vigil, was born in Sopris, a small coal mining community along the Purgatoire River in southeastern Colorado. Flooding wretched havoc on communities in the river's floodplain until the construction of Trinidad Reservoir. Sopris and several neighboring communities were buried beneath the rising water. My brother, Nathan Tye, and I compiled our grandfather's records and created a website (www.sopris.co) to share the history of this community and honor its residents. Background images are modified USGS satellite imagery from 1971 and 2016, respectively.

Day roost selection

Limited information is available about bat roosts in riparian corridors of the southwestern United States. This region is increasingly threatened by climate change, severe drought, and overuse of freshwater resources. We used radiotelemetry to document day roosts of four Myotis species (M. auriculus, M. occultus, M. thysanodes, and M. yumanensis) along the Mimbres River, one of the last naturally-flowing waterways in New Mexico. Our data represented some of the first documented roosts for these Myotis species in several deciduous tree species, arid riparian corridors, and New Mexico.

Life of a North American beaver lodge

North American beavers (Castor canadensis) inhabit and modify waterbodies throughout the continent. Positive associations between various beaver-modified terrains and non-beaver fauna are well-documented, though limited information is available about species directly associated with beaver structures. For the past several years, Michael Forsberg, the Platte Basin Time-lapse Project, and I have used time-lapse photography to document the structural and ecological dynamics of a beaver lodge in a human-made lake near the Platte River in south-central Nebraska. To date, we have collected over 200,000 images and 3,000 videos that detail the life history of a beaver colony and the wide variety of organisms that make use of their lodge. Images property of Michael Forsberg and the Platte Basin Timelapse Project. Data visualizations created in R with the activity package and modified with Adobe Illustrator CC.

Night-roosting behaviors

The northern long-eared myotis (Myotis septenrionalis) has experienced pervasive population declines in eastern portions of its distribution and is currently listed as threatened and endangered in the United States and Canada, respectively. We used time-lapse photography to document night-roosting behaviors of this imperiled species beneath a wooden bridge in northwestern Nebraska. This region harbors some of the species' westernmost populations in the United States, which will be the last populations affected white nose syndrome. Images property of Keith Geluso. Video created in Adobe After Effects CC.

Sounds of the Platte River Valley

Ben Gottesman, a doctoral candidate at Purdue University's Center for Global Soundscapes, collected years of bioacoustics data to examine wildlife communities near the Platte and Niobrara Rivers. As his technician, I maintained acoustic recorders (right) mounted near solar-powered, DSLR camera systems (left) owned by the Platte Basin Timelapse Project to document the sights and sounds of threatened prairie ecosystems. This collaboration elucidated temporal partitioning by resident and migratory species at regional conservation areas, as well as provided reliable long-term datasets of grassland bird phenologies.