INTEGRATED RECOVERY RECAPTURE DATA-ANALYSIS

The integration of recovery and recapture data, providing information on the same individuals, is important for the stable fitting of a wide range of stochastic models, resulting in more realistic estimates of survival probabilities of wild animals than when either the recovery o r recapture data are used separately. Previous integrated analyses hav e either concentrated on time-dependent parameters only or, in the age -dependent case, have not provided a flexible framework for model refi nement and selection. We derive the likelihood for a general integrate d model, allowing both age-and time-dependent parameters. The work of this paper was motivated by a set of recapture histories on shags (Pha lacrocorax aristotelis), for which biological knowledge and previous d ata analysis suggest age dependence in both survival and recapture pro babilities. We use these data to illustrate the general method. All mo del fitting is done by the method of maximum likelihood and the progra mming is done in MATLAB. For the shags, we found an annual survival pr obability of 0.87 (standard error 0.01) for birds of breeding age and 0.70 (0.02) for birds in their second and third years. First-year surv ival varied widely with time about an average of 0.46.