Passerine and secretive marsh bird responses to cattail management in temperate wetlands

Abstract

Hybrid cattails (Typha x glauca) are an invasive, emergent aquatic plant that often form monodominant stands, which can alter wetland vegetation structure and negatively affect wildlife populations. Wetland managers often apply prescribed burning, grazing, and herbicide treatments to reduce cattail density but how these management actions influence wetland wildlife is largely unknown. Our objectives were to investigate the effect of hybrid cattail control methods on secretive marsh bird and wetland passerine abundance in central Minnesota, USA. Specifically, we assessed how environmental variables and cattail treatments (e.g., burning, grazing, and herbicide) influenced bird densities and community composition. We used the North American Marsh Bird Monitoring Protocol to assess wetland bird communities across sixteen wetlands comprised of eight treatments with a full-factorial design. Species-specific density estimates and community-wide ordination offered little evidence for a substantial effect of treatments on marsh birds and passerines. However, gradients in vegetation height and mean biomass did have a significant relationship with both passerine and marsh bird community composition, which suggests changes in the bird community following cattail management might require time to develop. To support diverse wetland bird communities, treatments must create contrast among wetland habitats with high and low vegetative biomass. Because secretive marsh birds are under-surveyed, our baseline population estimates are valuable for future local and regional management and for gaining preliminary understanding of the effect of invasive species management on wetland birds in the Upper Midwest.