MATLAB: An environment for analyzing ring-recovery and recapture data

The programming environment provided by MATLAB makes it easy to write code for the interactive analysis of data from ring-recovery and recapture studies. In particular, it is simple to write down a log-likelihood for any given model, to maximize this log-likelihood to estimate the parameters of the model and calculate their standard errors, to perform likelihood ratio and score test comparisons of models, and to compute goodness-of-fit statistics and examine residuals. Eagle is a package of simple MATLAB programs that provides an interactive environment for the analysis of ring-recovery data. Eagle will cope with any model of the Freeman-Morgan kind, where the survival and recovery probabilities may be specified as constant, time- or age-dependent, or as depending on one or more external covariates. This will be extended to handle data from recapture studies and from combined recovery and recapture studies. The package may also be used to analyze arbitrary models, at the expense of a small amount of extra MATLAB programming. A demonstration is given of use of Eagle to analyze data from a ring-recovery study on grey herons (Ardea cinera), with and without covariates. The use of the MATLAB programming environment is illustrated by fitting a simple model to some recapture data on herring gulls (Larus argentatus).