Are Ephemeral Wetlands Hotspots for Avian Biodiversity in Pine Savanna Habitats?

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Barratt Heitmann, Jackson
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The purpose of this study was to examine the biodiversity of songbird communities in isolated wetlands distributed across pine savanna ecosystems. Specifically, we tested if bird biodiversity was higher in ephemeral wetlands compared to surrounding upland savannas, if the degree of species turnover, or beta diversity, was different between wetlands and uplands, and finally what environmental variables drove species composition and biodiversity within ephemeral wetlands. We conducted avian point count surveys, vegetation surveys, and LiDAR surveys of n=19 wetlands and n=6 uplands in 2021, and n=30 wetlands and n=6 uplands in 2022, on 2 properties with pine savanna habitats. We used direct ordination methods, and linear mixed effect models to 1) analyze differences in bird biodiversity and community composition in ephemeral wetlands compared to surrounding uplands, and to 2) analyze within wetland bird biodiversity driven by vegetation and environmental variables like canopy cover and basal area. We found that wetlands were significantly more diverse (across multiple diversity metrics) and had more birds than uplands, but that spatial variation in species composition was generally similar within wetlands and uplands. Species such as Blue-gray Gnatcatcher, White-eyed Vireo, and Northern Parula were more common in wetland habitats. We found that higher canopy cover was associated with significantly higher abundance of birds in ephemeral wetlands, but variation in wetland biodiversity and species composition was largely unexplained by measures of vegetation productivity. Ephemeral wetlands are important repositories of bird biodiversity, and should be prioritized by land managers for their ecological value.