Document Type
Thesis
Date of Award
2025
Degree Name
Master of Science (MS)
Department
Biology
First Advisor
David Swanson
Abstract
The Interior Least Tern (Sterna antillarum athalassos) has experienced significant conservation success, culminating in its removal from the federal endangered species list in 2021. However, the species remains state-endangered in South Dakota, and knowledge gaps persist regarding its foraging ecology and population dynamics along the Missouri National Recreational River (MNRR). This study aimed to address these gaps by quantifying Least Tern abundance, nesting productivity, and movement patterns between nesting and foraging sites during the 2024 and 2025 breeding seasons. We conducted surveys of Least Terns on riverine sandbars and off-river wetlands within a 30-km radius of the MNRR, employing both direct observation and automated telemetry (VHF and Motus tags) to track adult movements. Nesting success was monitored using GPS-marked nests and field observations, and population abundance was estimated by conducting systematic surveys at on-river sandbars and off-river wetland sites. The 2025 census documented a record 651 adult Least Terns within the 59-mile reach of the MNRR. Nesting productivity was highly variable, with flooding events in 2024 causing significant nest loss and habitat degradation. Tracking and off-river abundance survey results indicate that Least Terns utilize both on-river and off-river habitats for foraging, with some individuals traveling long distances between nest sites and foraging locations. These findings highlight the importance of both riverine and adjacent wetland habitats for Least Tern conservation and underscore the need for adaptive management strategies that address ongoing threats such as sandbar nesting habitat loss, declines in shallow-water foraging habitat and prey fish species abundance, hydrologic alteration, and climate-driven disturbance. The study provides critical data illuminating connections between on-river and off-river habitats, which will inform state-specific delisting criteria and guide future management of Least Tern populations in South Dakota.
Subject Categories
Biology
Keywords
Interior Least Tern; Sterna antillarum athalassos; Missouri National Recreational River; breeding ecology; nesting productivity; population abundance; foraging ecology; movement ecology; telemetry; sandbar nesting;
Number of Pages
63
Publisher
University of South Dakota
Recommended Citation
Jorgensen, Kyle, "Least Tern Abundance, Nesting Productivity, and Dispersal Between Nesting and On- and Off-river Foraging Sites in the Missouri National Recreational River" (2025). Dissertations and Theses. 385.
https://red.library.usd.edu/diss-thesis/385