Introduction

Survivorship, the proportion of individuals surviving throughout a given period, may be estimated simply as p = x/n where n = the number alive at the start of the period and x equals the number alive at the end of the period, or it may be estimated using capture–recapture methods as discussed in Chapter Nine. Two additional issues, however, often arise in behavioral ecology. One is that in many studies a measure of overall survival across several periods, each having a separate survival estimate, may be desired. The second issue is that in studies of nesting birds or other animals, information is often incomplete because many nests are not discovered until well after they have been initiated and may not be followed to completion. In this Chapter we discuss methods developed to handle both of these cases. We focus on telemetry studies, which raise the first issue, and studies of nesting success which raise both issues.

Telemetry studies

In telemetry studies, transmitters are attached to animals which are then monitored for various purposes, including the estimation of survival rates. The simplest case arises when all transmitters are attached at about the same time and animals are checked periodically at about the same times until they die or the study ends. Cohorts based on age, sex, or other factors may be defined.

Data of this type are basically binomial (White and Garrott 1990; Samuel and Fuller 1994). On any sampling occasion, t, the proportion of animals still alive is the appropriate estimator of survivorship to that time.