Common Terns on Oneida Lake

Jennifer Arnold, Stephen Oswald, Paul Curtis (Funded by NYSDEC)

In 2024, research and monitoring of Common Terns was continued at Oneida Lake. This project has continued since 1979 and represents an important resource for understanding pressures on declining inland populations of this species. Lilah Bricker (field tech) and Kyla Ebersole (CBFS intern) returned to work on the project. Additionally, Shannon Hu undertook work on tern diets as a CBFS intern in a collaboration between waterbird and warm-water fisheries research. Additionally, two Penn State alumni, along with other CBFS interns, participated in day trips to the tern breeding islands to contribute to waterbird research and management efforts.

Our peak nest count (June 11) was 404 Common Tern nests between two islands. This year, despite installed gull exclusion grids and measures to attract terns, tern numbers were lower on Willard Island, which was repeatedly eroded, leading to tern nest loss and use as a roosting area by other waterbirds. Instead, tern numbers increased on Little Island, which has lost 60% of its area since 2009. This led to high nesting densities and relatively low breeding productivity, and many nests were in unsuitable areas and were washed out. We also used remote surveillance to detect predators, disturbances, and to guide the adaptive management of breeding terns throughout the season. Across both islands, breeding success was estimated as 0.41 chicks per nest surviving to fledging (estimated at 18 days of age), which is at the lower end of recent years and is less than half that needed for the colony to be self-sustaining. The ongoing over wash and erosion of breeding islands pose a threat to the persistence of Common Terns as a breeding species at Oneida Lake, necessitating the restoration of tern breeding islands.

Research this year included studies of diet through genetic metabarcoding (with Gemma Clucas, Cornell Lab of Ornithology), behavioral observation (Shannon Hu) and remote methods, exploring soundscapes as a management tool at tern colonies (Kyla Ebersole) and employing mark-recapture techniques to study population demography. All these studies will contribute to inform management of this and other inland tern colonies to promote conservation of this state-listed species.