Estimating Effects of Habitat Characteristics on Abundances of Three Species of Secretive Marsh Birds in Central Florida

Wetland loss has led to population declines of many species of North American marsh birds. However, due to the secretive nature of many of these species, there is uncertainty about their population status and habitat requirements. Recently developed techniques, such as the Standardized North American Marsh Bird Monitoring Protocol and analytical methods that account for variable detection probabilities, can be used to improve both the quality and quantity of information about secretive marsh birds. In 2009 and 2010, point counts were conducted using the marsh bird monitoring protocol to count Least Bittern (Ixobrychus exilis), Purple Gallinule (Porphyrio martinica) and Limpkin (Aramus guarauna) in the Kissimmee Chain of Lakes, Florida. Habitat factors thought to influence abundance were compared using competing hierarchical mixture models. Abundance of Least Bittern had a positive relationship with amounts of emergent vegetative cover and interspersion (i.e., vegetation to water edge). Purple Gallinule abundance was positively related to percentage of area cover by floating-leaved vegetation, interspersion and diversity of vegetation type. Limpkin abundance was non-linearly related to vegetation cover in both years. In 2009, Limpkin abundance was positively related to vegetation to water edge and vegetation type diversity, and negatively related to vegetation edge in 2010. Results demonstrate that marsh habitats with greater amounts of vegetative cover, interspersion, and vegetation diversity will support the greatest abundance of this suite of marsh birds.