Bart Kempenaers

Introduction Predators of ground-nesting birds use a variety of cues to locate nests, including visual, olfactory, and acoustic signals. However, we have limited knowledge of the exact mechanism of how predators find nests (Vickery et al. 1992, Pelech et al. 2010, Ibáñez-Álamo et al. 2015).

1 INTRODUCTION In birds, eggs typically hatch after a period of incubation by one or both parents. However, for various reasons, hatching may fail. For example, eggs may fail to develop as a result of male or female infertility (Santema et al., 2020), or the embryo may die at an early stage due to genetic defects (Briskie & Mackintosh, 2004; Cordero et al., 2004; Heber & Briskie, 2010) or because of chemical pollution (Assersohn et al., 2021; Janssens et al., 2003).

Model structure To describe effects of age on extra-pair siring success, we inspected the relationship between male age and (a) the probability of siring at least one EPY, (b) the number of extra-pair mates and (c) the total number of EPY sired, as well as the proportion of EPY sired among all genotyped eggs laid by the respective extra-pair female(s). All models were generalized linear mixed-effect models (GLMMs) fitted using the R-package ‘lme4’ (version 1.1.23, Bates et al., 2015).