|Session I: Upland Plants
||Abstract #: 97103
ENVIRONMENTAL VARIABLES AFFECTING WADING BIRD FORAGING SUCCESS IN THE
James Surdick Jr. and Dr. Peter Frederick
University of Florida, Homestead, FL 33031
Large populations of breeding wading birds have been suggested as key indicators of Everglades restoration, and breeding success has been linked directly with availability of food. However, factors driving food availability are poorly understood, and knowledge of these factors may have direct implications for water and vegetation management strategies. Through direct observation of foraging success and foraging conditions, we are attempting to identify the combinations of environmental conditions (primarily water depth, vegetation density and prey density) which influence foraging success of wading birds in freshwater Everglades marshes. We are measuring foraging success of birds feeding at 17 sites throughout the Water Conservation Areas and Everglades National Park, where bimonthly prey density measurements are already underway by collaborators Joel Trexler and Frank Jordan. Measurements of vegetation, water depth, temperature and clarity, weather, substrate and social context are also made at the time of observation.
During winter and spring of 1996 and 1997, we conducted over 1,500 observations of Wood Storks, White Ibis, Great Egrets and Snowy Egrets at a variety of sites throughout the Everglades. Several significant univariate correlations were found between capture rate and various environmental variables: Snowy Egrets (periphyton coverage, emergent vegetation, water depth and wind speed); Great Egrets (flock size, periphyton coverage, emergent vegetation, water depth and water temperature); and Wood Storks (time of day, water depth, water temperature and wind speed). Along with daily foraging observations, monthly aerial surveys are conducted at each site to measure their relative attractiveness to wading birds. If the impacts of various environmental variables on wading bird foraging success can be identified, this study may help us become better stewards of the Everglades and increase our knowledge of wading bird ecology.