Great Lakes coastal wetlands as suitable habitat for invasive mute swans in Michigan

Abstract

Great Lakes coastal wetlands provide critical habitat and food resources for more species than any other Great Lakes ecosystem. Due to past and current anthropogenic disturbances, coastal wetland area has been reduced by >50% while remaining habitat is frequently degraded. Invasive mute swans have contributed to the degradation of coastal wetlands by removing submergent vegetation and competitively excluding native species from breeding areas and food resources. Despite current control practices, mute swan population estimates in Michigan are ~8000, comparable to population estimates in the entire Atlantic Flyway of North America. We collected local abiotic data and adjacent land cover data at 3 scales from 51 sites during 2010 and 2011 and conducted 2 mute swan detection surveys each year during the summer and fall. We developed a single-species, single-season occupancy-based habitat suitability model to determine current and potential mute swan habitat among Great Lakes coastal wetlands. We found mute swans occupied heterotrophic coastal wetlands adjacent to urban areas, which were high in ammonium and oxidation-reduction potential and low in nitrates, dissolved oxygen, and turbidity. Our model provides managers with a valuable tool for rapidly identifying mute swan habitat areas for control efforts, particularly the need for targeting mute swan populations in or near urbanized areas. Our model will also aid managers in monitoring areas that mute swans may invade and prioritizing coastal wetland areas for restoration efforts.