The Distribution of Common Loons (Gavia immer) Overwintering on a Freshwater Reservoir
Confirmation
1
Document Type
Poster
Start Date
11-4-2025 12:00 PM
End Date
11-4-2025 12:50 PM
Abstract
The common loon (Gavia immer) is traditionally known to overwinter in coastal marine environments, yet little research has been conducted on those loons that overwinter on freshwater reservoirs. Lake Jocassee is a freshwater reservoir in northwest South Carolina where loons have overwinter in significant numbers. Past work has shown that these loons differ significantly in the degree of sociality. Some individuals are solitary, spending70% of their time with conspecifics. Using census data collected between 2018 and 2024, we examined patterns in the distribution of each of these three types of loons. We employed ArcView Geographic Information System software to analyze GPS location of solitary, loosely social, or strongly social individuals. We found highest loon densities were consistently within the Upper Toxaway area of the lake, with solitary loons favoring the Lower Toxaway, while strongly social loons predominantly occupied the Howard Creek arm. These findings support the hypothesis that loon distribution is influenced by lake morphology and the degree of sociality, with river mouths—rich in nutrients and assemblages of forage fish—being preferred habitats for social loons. More robust surveys of fish population assessments would facilitate our understanding of habitat selection and social behavior among overwintering loons.
Recommended Citation
Offenbaker, Kirsten; Mager, Jay; Rossiter, Katy; Paruk, James; Abts, Sherri; and Wade, Brooks, "The Distribution of Common Loons (Gavia immer) Overwintering on a Freshwater Reservoir" (2025). ONU Student Research Colloquium. 82.
https://digitalcommons.onu.edu/student_research_colloquium/2025/Posters/82
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The Distribution of Common Loons (Gavia immer) Overwintering on a Freshwater Reservoir
The common loon (Gavia immer) is traditionally known to overwinter in coastal marine environments, yet little research has been conducted on those loons that overwinter on freshwater reservoirs. Lake Jocassee is a freshwater reservoir in northwest South Carolina where loons have overwinter in significant numbers. Past work has shown that these loons differ significantly in the degree of sociality. Some individuals are solitary, spending70% of their time with conspecifics. Using census data collected between 2018 and 2024, we examined patterns in the distribution of each of these three types of loons. We employed ArcView Geographic Information System software to analyze GPS location of solitary, loosely social, or strongly social individuals. We found highest loon densities were consistently within the Upper Toxaway area of the lake, with solitary loons favoring the Lower Toxaway, while strongly social loons predominantly occupied the Howard Creek arm. These findings support the hypothesis that loon distribution is influenced by lake morphology and the degree of sociality, with river mouths—rich in nutrients and assemblages of forage fish—being preferred habitats for social loons. More robust surveys of fish population assessments would facilitate our understanding of habitat selection and social behavior among overwintering loons.