Factors affecting Bittern Botaurus stellaris distribution in a Mediterranean wetland

Abstract

The habitat requirements of a resident population of Bittern Botaurus stellaris were investigated during the breeding season in a Mediterranean upland wetland, with particular reference to the area's isolation from other wetlands, its small size and hydrological conditions. Vegetation structure and water-level were described and associated with booming male and nesting female distribution within the marsh. A logistic regression model showed that water-level was the only significant factor affecting the distribution of booming males, which occupied areas seasonally flooded with shallower water (< 1 m). Females nested in seasonally flooded zones, while vegetation density appeared an important variable for nesting-site choice. Management of the wet area is discussed and the importance of a better understanding of the temporal dynamics of vegetation cover and spatial and temporal variations in water-level, and their possible effects on prey distribution, is highlighted.