The Composite Dynamic Method as Evidence for Age-Specific Waterfowl Mortality

Abstract

For the past 25 yr estimation of mortality rates for waterfowl has been based almost entirely on the composite dynamic life table. The specific assumptions for this method were examined and a valid goodness of fit test was derived. This test was performed on 45 data sets representing a cross section of banded samples for various waterfowl species [mallard, blue-winged teal, pintail, wood duck, lesser scaup, redhead, canvasback, wigeon and green-winged teal], geographic areas, banding periods and age/sex classes. The composite dynamic method was rejected (P < 0.001) in 37 of the 45 data sets (in fact, 29 were rejected at P < 0.00001) and recovery and harvest rates are year-specific (a critical violation of the necessary assumptions). The restrictive assumptions required for the composite dynamic method to produce valid estimates of mortality rates are not met in waterfowl data. Even when the required assumptions are met, the method produces very biased estimates of age-specific mortality rates. The composite dynamic method should not be used in the analysis of waterfowl banding data. The composite dynamic method does not provide valid evidence for age-specific mortality rates in waterfowl.