Modeling heterogeneity in nest survival data

Current statistical methods for estimating nest survival rates assume that nests are identical in their propensity to succeed. However, there are seve ral biological reasons to question this assumption. For example, experience of the nest builder, number of nest helpers, genetic fitness of individual s, and site effects may contribute to an inherent disparity between nests w ith respect to their daily mortality rates. Ignoring such heterogeneity can lead to incorrect survival estimates. Our results show that constant survi val models can seriously underestimate overall survival in the presence of heterogeneity. This paper presents a flexible random-effects approach to mo del heterogeneous nest survival data. We illustrate our methods through dat a on redwing blackbirds.