Influence of invasive hybrid cattails on habitat use by common loons

Abstract

ABSTRACT An invasive hybrid cattail species, Typha × glauca (T. × glauca), is rapidly expanding across the United States and Canada. Dense clonal stands of T. × glauca outcompete native wetland plants, reduce open‐water habitats, and negatively affect native wetland plant diversity; however, effects of hybrid cattail expansions on native wildlife are still unclear. We used multiple surveys and single‐season occupancy models to examine how the relative coverage of T. × glauca affected habitat use by common loons (Gavia immer) at 71 wetland sites in Voyageurs National Park, Minnesota, USA, during summer 2016. Delineated wetland sites (2 ha) were considered potential resource patches for common loons and positioned along a gradient of relative T. × glauca coverage. Detection of common loons was influenced negatively by the time of day surveys were conducted. Occupancy probabilities were greater at sites with deeper water levels, possibly indicating selection for areas with adequate water depths for pursuit‐based foraging for fish. Contrary to our hypothesis, common loons appeared insensitive to the relative coverage of T. × glauca at wetland sites. Future research should focus on elucidating potential threshold‐effects of T. × glauca expansions on additional loon demographic rates. © 2018 The Wildlife Society.

Keywords

• cattails
• common loon
• Gavia immer
• invasive species
• T. × glauca
• Voyageurs National Park