Session VI: Bird & Animal Studies

Abstract #: 97601

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SOURCES OF VARIATION IN ANNUAL COUNT DATA USED TO ESTIMATE THE NUMBER OF SNAIL KITES IN FLORIDA
Victoria J. Dreitz,Robert E. Bennetts, and Wiley M. Kitchens
Dept. Biol., Univ. of Miami, Coral Gables, FL; Coop. Fish and Wild. Res. Unit, Gainesville, FL; & U.S. Geological Service, Coop. Fish and Wild. Res. Unit, Gainesville, FL

ABSTRACT
Since 1969 the number of Snail Kites (Rostrhamus sociabilis) in Florida has been monitored via a quasi-systematic annual count. Numerous biological interpretations have been derived from these counts assuming that the counts represent complete censuses. Often the interpretations have little or no regard for the inherent sources of variation in these data that could influence the validity of subsequent interpretations. Here we examine several sources of variation inherent in the annual count and present data showing how several systematic sources of variation can greatly influence the probability of detecting individuals on any given count. We suggest that capture-recapture (mark-resighting)techniques offer a reasonable alternative for estimating populations size. This approach enables explicit estimation of the probability of detecting individuals. We present preliminary results using this technique to estimate population size of Snail Kites in Florida.