Modelling Heron Survival Using Weather Data

Abstract

There is a definite needfor methodology which will produce ageand time-specific survival probabilities from bird ringing studies in which only nestlings are ringed, and one possible approach to this problem is presented in this paper. Models are developed in which the survival rates for first-year birds are weather-dependent (and therefore time-speeific) and the rate for second-year birds is a constant, difterent from the constant annual survival rate assumed for all older birds, to describe the numbers of recoveries of rings from dead Grey Herons, A rdea cinerea, ringed as nestlings in Britain between 1955 and 1975. The models provide a good fit to the data and a useful and concise description of Heron survival. Comparison is made with the predictions of a modelfor heronry census data.