SEASONAL AND HABITAT INFLUENCES ON AVIFAUNA OF AN AGRICULTURAL IMPOUNDMENT IN SOUTHWEST FLORIDA: RESULTS OF A FIVE-YEAR MONITORING PROGRAM

Agricultural impoundments represent potentially important habitat, but little information is available on the use of these areas by wildlife or how that use varies seasonally. We conducted weekly surveys during a 5-year period to document seasonal, annual, and habitat influences on the avian community of a 10.5-ha agricultural impoundment in southwest Florida. The impoundment included a mix of wetland and upland cover types typical of impoundments in the region. We recorded approximately 1/3 of the 229 potential native resident and migratory avifauna known to occur in the region, including 5 species of state or federally listed wading birds. Of the 85 species documented, 65% nested in southwest Florida, many of which were augmented by winter migrants. The avian assemblage was relatively evenly distributed and 5 of the 7 defined guilds were represented among the 8 most abundant species. Wetland cover types attracted the most species and birds, many of the most abundant of which were species known to use wetlands with relatively dense vegetation. Seasonal effects associated with changing wetland conditions and migratory species were principal factors influencing changes in the bird community. Numbers of species and birds were inversely related to the rainy summer months and positively associated with improved foraging conditions created by seasonal changes in water level. Annual effects were less important but species and numbers of birds declined during the year of lowest annual rainfall. Southwest Florida has thousands of hectares devoted to agricultural impoundments, the collective contribution of which may be extremely important for conservation of regional and migratory bird populations, yet almost nothing is known about the value of these habitats in working landscapes or how best to manage them for wildlife.