WEIGHTED NEST SURVIVAL MODELS

Nest survival data possess two characteristics that are not fully expl oited by traditional nest survival models: the data constitute a proba bility sample of the population and the length of time nests are obser ved provides information concerning age at the time of detection. Mode ls that fail to acknowledge the probabilities with which nests are inc luded in the sample are strictly conditioned on the observed, typicall y biased, data. In addition, if knowledge of the age at the time of de tection is not utilized, the information contained in the data is not fully exploited. This paper presents a general model for the probabili ty density function (pdf) of data observed in nest survival studies. T he model incorporates both probabilities of inclusion and information concerning the age of nests at the time of detection. Maximum likeliho od estimators of all parameters involved in the pdf, including surviva l rates, are based on the pdf of the observed data rather than the pdf of variables in the population. The nest survival model of Pollock an d Cornelius (1988, Biometrics 44, 397-404) is a special case of the ge neral model.