Colonial waterbirds have impacted forested island ecosystems throughout their breeding range, changing vegetation, and soil characteristics and bird communities. Our objectives were to (1) determine effects of three levels of colonial waterbird exclusion on overall vegetation diversity and growth, and survival of a candidate restoration species (black elderberry; Sambucus nigra canadensis); (2) investigate effects of different planting techniques on survival and growth of black elderberry; and (3) determine effects of waterbird colonization on soil chemistry. In 2012, we investigated effects of three levels of waterbird exclusion (none control plots [CON]; partial, which excluded waterbirds larger than gulls [PEX]; and full which excluded all waterbirds [FEX]) on bird use, existing vegetation growth and diversity, and survival of planted black elderberry on three islands in Door County, WI, Lake Michigan. In 2013, we evaluated survival of black elderberry established with four planting treatments within three waterbird exclusion treatments on two islands in 2013. We also compared soil chemistry characteristics between islands with and without nesting waterbirds for 2 years. Overall plant growth was greater in exclosures, but elderberry survival was similar among treatments. Soil replacement and weed suppression planting treatments did not affect survival, but generally increased overall elderberry biomass. Soil from nesting islands was more acidic and had greater nutrient concentrations than reference islands. Exclusion or removal of colonial nesting waterbirds from islands may improve overall vegetation growth, but successful restoration of woody vegetation may require significant soil manipulation and planting.

Anthropogenic inputs of heavy metals and metalloids pose a risk to wetland ecosystems due to their long retention time in sediment, high toxicity at low concentrations, and ability to biomagnify in the food chain. Our study involved an extensive monitoring effort for seven heavy metals (cadmium:Cd, chromium:Cr, copper:Cu, mercury:Hg, nickel:Ni, lead:Pb, zinc:Zn) and one metalloid (arsenic:As) in sediment, roots of the invasive hybrid cattail (Typha x glauca), and livers from muskrats (Ondatra zibethicus) at Horicon National Wildlife Refuge, a wetland of international importance in southeastern Wisconsin, United States. Overall, our comparison to literature values and thresholds led us to conclude that heavy metals and metalloids pose a low risk to the refuge. The highest concentrations were found in the sediment, followed by T. x glauca roots, and with negligible concentrations in muskrat liver tissue for all but the essential metals Cu, Ni and Zn, indicating low biomagnification in this food chain. A spatial analysis using GIS revealed hotspots for Cd, Cr, Cu, Ni, and Zn in sediment in one particular subplot, which we hypothesize may be from runoff of agricultural amendments. However, since concentrations in sediment were similar to or lower than concentrations found in a prior survey from 1990, there may have been improvement over the last three decades. Overall, while anthropogenic influences are present, we recommend that our relatively low concentrations be used as healthy points of comparison regarding risk to plants and mammals for others conducting metal and metalloid surveys on wetlands.