Waterbird Habitat Selection in Georgetown County, South Carolina 

Wetland habitats are ecologically valuable due to their high biological diversity and productivity, with many avian species depending on them. Understanding how waterfowl select habitats for use is essential to successful wetland management. The southeastern coastal plain of the United States contains 27% of the wetlands within the lower 48 states. However, only about 9% of these wetlands are of high or moderate value to waterfowl and other waterbirds. The region is comprised of 7 main wetland type classifications: (1) estuarine deepwater, (2) estuarine wetland, (3) freshwater emergent, (4) freshwater forested and shrub, (5) freshwater ponds, (6) lakes, and (7) riverine wetlands. Despite the significance of the Hobcaw Barony in a region historically known as a waterfowl hunting paradise, the long history of the Belle W. Baruch Institute of Coastal Ecology and Forest Science on Hobcaw Barony and the establishment of the James C. Kennedy Waterfowl and Wetlands Conservation Center at the Baruch Institute in 2014, no comprehensive study of waterbirds has occurred on site. Thus, this study aims to form a fundamental baseline of wetland and waterbird data as the beginning of a long-term dataset. Our specific objectives were to 1) determine which wetland type is hosting the most waterbirds in terms of species diversity and abundance and 2) determine what environmental factor(s) are contributing to the most productive wetland type at Hobcaw Barony and DeBordieu Colony. 

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This study along the South Carolina coast began in January of 2022, encompassing extensive, conserved lands and highly developed and altered landscapes. Two field seasons have since been completed from February-July of 2022 and January-July of 2023. Research sites were at the Hobcaw Barony (~7,000 ha) and the DeBordieu Colony (~1,000 ha).  

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In 2022, we performed point count surveys at 95 randomly selected wetlands, varying by type, and secretive marshbird surveys at 10 emergent wetlands to estimate occupancy rates, species diversity, species abundance, and migration chronology. In 2023, we performed point counts in 98 randomly selected wetlands and secretive marshbird surveys in 8 emergent wetlands. In year 2, we readjusted and maximized sampling effort on wetland types where waterbirds were most abundant and decreased on the remaining types (based on the availability of time to survey) where few birds were observed, surveying in 98 wetlands. Wetland-level data (e.g., water quality, water regimes, vegetation, macroinvertebrates) were also collected to model waterbird use and selection of wetlands. To determine which environmental factor(s) were driving waterbird attraction, we will perform a generalized linear mixed model with a Poisson distribution for each species guild and our top 12 detected species.  

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We detected 4,099 waterbirds over our two field seasons. We observed 56 species, with 34 of those species seen in both field seasons, 8 species unique to 2022 and 13 species unique to 2023. We observed 1,518 wading birds (10 species), 744 shorebirds (16 species), 844 waterfowl (13 species), 347 marshbirds (6 species), 161 gulls-terns (6 species), 445 anhingas-cormorants-pelicans (4 species), and 40 grebes (1 species). Preliminary results from the generalized linear model for waterfowl reveal that the following environmental factors have a significant effect on their presence: location, wetland classification, vegetation distribution pattern, water regime, wind direction, distance to nearest wetland, wetland area, macroinvertebrate species richness, and percent vegetation cover. Waterfowl had a significant positive relationship with DeBordieu, specifically, lacustrine limnetic unconsolidated bottom wetlands (i.e., lakes) and permanently flooded open-water wetlands. These results are no surprise as DeBordieu contains primarily this wetland type, and historically, this wetland type highly supports waterfowl species.  

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This study would not have been possible without funding support from the DeBordieu Colony and the James C. Kennedy Waterfowl and Wetlands Conservation Center, and logistical support from the Nemours Wildlife Foundation, Belle W. Baruch Foundation, and Clemson’s Department of Forestry and Environmental Conservation. We also appreciate Jack Corbin, Anna Koon, Carly Sprott, and Blair Abernathy for their assistance in the field.