Examining Avian Communities in Wetlands at Multiple Spatial Extents
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Destruction and impairment of wetlands has been extensive throughout the conterminous United States, resulting in the loss of both crucial ecosystem functions and productive habitat for a wide variety of organisms. Over the last few decades, efforts to protect, restore, and create wetlands have led to increases in wetland area and improvements to wetland quality in many locations. However, wetlands are difficult to create or restore, and whether these initiatives will lead to wetland function that approaches historical levels remains unclear. My research focuses on how the diverse bird communities that rely on wetlands might be affected by changes to their primary habitat and the surrounding landscape. I utilized data from the North American Breeding Bird Survey (BBS) and the National Land Cover Database (NLCD) to develop a set of spatially-explicit abundance models for each of 31 species of wetland-breeding birds. Independent variables in these models included combinations of three different aquatic habitats as well as other land cover types that could potentially influence species abundance. I compared the models in an information-theoretic framework to determine which cover types most influenced species abundance. All species were positively associated with one or more types of aquatic cover, and when considered in the broad spatial context of entire landscapes, other cover types likely affect abundances of many species as well. Next, I conducted a review of previously published studies on avian use of anthropogenic wetlands, including a meta-analysis that compared wetland bird community metrics between anthropogenic wetlands and reference sites. My results suggested that while created and restored wetlands do support many avian species, these communities are typically dissimilar from those at natural wetlands. Finally, I used data from the BBS and the NLCD to describe the characteristics of wetland bird communities and the composition of the landscape (including how these factors have changed over time) at the level of the Bird Conservation Region. These data indicate that both wetlands and the bird communities associated with these systems have experienced changes in recent years, but total regional wetland area has been fairly stable.