
For the past 25 years estimation of mortality rates for waterfowl has been based almost entirely on the composite dynamic life table. We examined the specific assumptions for this method and derived a valid goodness of fit test. We performed this test on 45 data sets representing a cross section of banded sampled for various waterfowl species, geographic areas, banding periods, and age/sex classes. We found that: (1) 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 (2) recovery and harvest rates are yearspecific (a critical violation of the necessary assumptions). We conclude that the restrictive assumptions required for the composite dynamic...

The estimation of animal abundance is an important problem in both the theoretical and applied biological sciences. Serious work to develop estimation methods began during the 1950s, with a few attempts before that time. The literature on estimation methods has increased tremendously during the past 25 years (Cormack 1968, Seber 1973). However, in large part, the problem remains unsolved. Past efforts toward comprehensive and systematic estimation of density (D) or population size (N) have been inadequate, in general. While more than 200 papers have been published on the subject, one is generally left without a unified approach to the estimation of abundance of an animal population This situation is unfortunate...

For valid statistical inference, it is important to select an appropriate statistical model. In the analysis of capturerecapture data under the closedpopulation models of Otis et al. (1978), information theoretic and hypothesis testing approaches to model selection are not practical, because some of the models have likelihoods with nonidenti fiable parameters. A further problem is that, for some of the Otis et al. models, multiple estimators exist but there is no objective basis for deciding which estimator to use for a particular dataset. In CAPTURE, a computer program for estimating parameters un der the closed models of Otis et al., a linear discriminant classifier is used to select an appropriate model....

Recently, Roseberry (1979) attempted to (1) clarify the theoretical basis for harvesting bobwhite (Colinus virginianus), (2) assess the impact of varying intensities of harvest on standing densities and longterm yields, and (3) define a harvest strategy appropriate for the bobwhite resource in Illinois. That paper, based on 24 years of field data, unfortunately contains 2 methodological or conceptual errors that are fundamental to the three objectives. Both errors are subtle, and as other have made the same or similar errors in analysis, we identify the problems in a way we hope will be taken constructively.

(1) The life table model is frequently employed in the analysis of ringer samples of young in bird populations. The basic model is biologically unrealistic and of little use in making inferences concerning agespecific survival probabilities. (2) This model rests on a number of restrictive assumptions, the failure of which causes serious biases. Several important assumptions are not met with real data and the estimators of agespecific survival are not robust enough to these failures. (3) Five major problems in the use of the life table method are reviewed. Examples are provided to illustrate several of the problems involved in using this method in making inferences about survival rates and its agespecific nature....

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