A synthesis of bird biodiversity studies in geographically isolated wetlands reveals research synergies and opportunities

Jackson Barratt Heitmann, Jiangxiao Qiu, Corey T. Callaghan 

Geographically isolated wetlands represent integral foraging and breeding habitat for many bird species across the United States, yet few studies have attempted to synthesize existing research to quantify generalizable relationships between bird biodiversity and geographically isolated wetlands. We conduct a systematic review of bird biodiversity in geographically isolated wetlands of the continental United States to explore the taxonomic and geographic areas of research and quantify the overarching themes in the literature. Most studies on bird biodiversity in GIWs come from the Midwestern United States, and only a third of all studies measured species richness and/or abundance for the entire avian community, with two thirds considering only a single taxonomic group (e.g., waterbirds) or a few key species (e.g., Black Tern, Northern Harrier, etc.). We find support from 15 US states for the species-area relationship for birds in geographically isolated wetlands. Semi-permanent wetlands (hydroperiod >9 months) support higher species richness of birds compared to seasonal or permanent wetlands, albeit most studies came from the Midwestern United States. Future research of bird biodiversity in geographically isolated wetlands is needed outside of the Midwestern United States, especially in high wetland cover areas like Florida or countries like Brazil and Botswana. Studies should also examine biodiversity metrics (e.g., phylogenetic or functional diversity) beyond abundance and species richness which do not capture the multifaceted nature of biodiversity. Long-term temporal and spatial analyses of community composition and organization are also needed to determine if bird communities are homogenizing through time or supporting especially unique communities across space.