Jessica Klassen, Ph.D. Candidate, Biological Sciences
Jessica Klassen, a Ph.D. candidate who works under Dale Gawlik in the Avian Ecology Laboratory, is not deterred by Florida’s “winter” temperatures. On one of the coldest mornings in January (a toasty 42 degrees) she and members of the team bundled up to go do their work deep in Florida’s Everglades.
Jessica’s research focuses on wading bird prey selection and what hydrologic conditions influence the type of prey consumed by wading birds. It is generally assumed that wading bird numbers and nest success will increase with the amount of fish in the landscape. However, there is very little work documenting what prey species make up the majority of wading bird diets. Her research provides a missing link in Everglades restoration planning by distinguishing between available aquatic prey, and those more likely to support a breeding colony. Additionally, her work looks at how prey selection may change in different hydrologic conditions, allowing insight as to what type of prey items may be more important to wading birds in wet versus dry years.
To answer these questions, Jessica visits various nesting sites to collect boluses (stomach regurgitations) from nestling wading birds including the Wood Stork, Tricolored Heron and Snowy Egret. On the chilly day in January, Jessica and the team took two airboats to lay trail - literally busting a path through the 15-ft tall grass that surrounds the nesting colony islands. The grass grows back after the nesting season, but it was vital to lay the trail far in advance of nesting season in order to not disturb the birds when they begin to nest. By creating a trail close to the island, Jessica can get in and out of the colony quickly and reduce disturbance to the birds when she starts visiting sites later this spring.
Her preliminary results indicate that wading birds select for the larger fish available in the landscape. This suggests that wading birds are more interested in fish that provide more calories per capture effort. However, there was a drastic rain event in the middle of the breeding season in 2012 which raised water levels. Following this event, she saw a dramatic shift in the wading bird’s ability to find these large, caloric prey items. Whereas some adult birds were still able to provide large prey items, most nestlings consumed a few, small prey species or none at all. However, the success of these few adults was limited as water levels remained high, and within a week all adults abandoned the colony.
Jessica is also developing models that determine what hydrologic and landscape characteristics produce pools of preferred prey species and prey with high body condition/calories. The goal is to use these models to guide water management practices that will aid in producing high quality prey items, while also predicting what prey type will be most available based on naturally dynamic hydrologic changes.