Session V: Bird Studies

Abstract #: 97503

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MEASURING AVIAN REPRODUCTION ON AN ECOSYSTEM SCALE: REPRODUCTIVE SUCCESS MEASURES ARE POOR PREDICTORS OF ANNUAL PRODUCTIVITY OF EVERGLADES WADING BIRDS
Peter C. Frederick
Dept. Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida 32611-0430

ABSTRACT
Avian nesting success measures are often assumed to accurately reflect local breeding conditions, but the scale dynamics of such linkages are poorly understood. Between 1986 and 1995, I measured numbers of nest starts, clutch size, nest survival, hatching success, and brood size of Great Egrets, White Ibises, Tricolored Herons and Snowy Egrets throughout the central Everglades, and estimated the annual ecosystem-wide productivity of these species. The only significant correlation among these annual measures was between numbers of nest starts and total production of young , and otherwise all combinations of annual measures were uncorrelated. This suggests that years of high recruitment within the ecosystem are inadequately predicted on a landscape scale by even ecosystem-wide measurement of reproductive success measures. The lack of concordance among variables also suggests that the predictability of reproductive success is quite low at any given point during the breeding season, due to both naturally-occurring and anthropogenic disturbance events. Wading bird restoration and monitoring efforts in the Everglades should concentrate on the features that attract large numbers of birds to nest, rather than attempting to maximize nest success parameters.