Non-existence of an optimum estimator in a class of ratio estimators

A number of estimators formulated in the field of the ratio method of estimation has been presented. A class of estimators encompassing these estimators is constructed. It is noted that an optimum estimator does not exist uniformly in this class. The “Optimum” so obtained reduces to the usual regression estimator.     

Estimation of trade-offs with capture-recapture models: A case study on the lesser snow goose

Trade-offs between traits such as fecundity or survival are fundamental to much of our understanding of the evolution of life histories. There has been much renewed interest and controversy concerning methods for estimating trade-offs, in the wild or in captivity, and with or without experimental manipulations. In this paper, we assess the general question of the utility of modern capture-recapture methods as a robust tool for estimating trade-offs in natural populations. We present results from analyses of two forms of trade-offs: the cost of present reproduction on future survival and the cost of present reproduction on the probability of breeding in the future. We apply the methods to data from a long-term study of a snow goose population, and generally discuss the advantages and potential problems with various approaches.