Wading Bird Foraging Patterns in the Southern Everglades: Correlation to Land Elements and Surface Water Pattern [Draft]

Foraging patterns of colonial wading birds (Ciconiiformes) in the 4300 sq km of the southern Everglades in Florida are described for 93 sampling dates during 1985 to 1995 based on observations from a systematic aerial sampling program. Sampling occurred primarily during the winter months (Dec-May) for each year with a mid-summer (August) sample. Additional months were included at the beginning of the program as well as just after hurricane Andrew. An index of bird abundance is used to examine temporal and spatial patterns as well as explore correlations with landscape and surface water coverage patterns. Location and counts of Great Egret (Casmerobous albas), Snowy Egret (Egretta thula), Great Blue Heron (Area heridus), Great White Heron (Ardea heridus occidentalis), White Ibis (Eudimicus alba), Glossy Ibis (Eudimicus niger), Wood Stork (Myrcia americana) and Roseate Spoonbill (Ajai ajai) were collected. Feeding guilds were created by pooling the above into the following: short-legged, tactile feeders (White Ibis, Glossy Ibis), long-·legged, tactile feeders (Wood Storks, Roseate Spoonbills) and long-legged, visual feeders (Great Blue Herons, Great White Herons, Great Egrets). The estimated numbers ofwading birds demonstrated a peak in January, 1993 with 90,035 birds, with a minimum estimated number of 1327 birds for May, 1990. All species and feeding guilds experienced declines from December to May, although the year-to-year pattern was not always consistent. Only a fraction of this temporal pattern can be attributed to hydrology changes, although it is clear that bird abundance was positively correlated with the fraction of total area classified as being of intermediate between wet or dry. Spatial patterns of bird occurrence was highly correlated with bird abundance which was also highly correlated with water condition changes which were themselves correlated to vegetation and other landscape patterns. This study clearly demonstrates the complexity of patterns of resource usage of colonial wading birds in the southern Everglades.