Association between nest defense and egg rejection behavior of Brown-breasted Bulbuls (Pycnonotus xanthorrhous)

Abstract

Different lines of host defense against parasites may be antagonistic or have additive benefits. For example, nest defense and egg rejection behaviors are important adaptations against brood parasitism in hosts that have been subject to much attention and numerous studies. However, the relationship between these 2 defensive behaviors within a single host population has hardly been elucidated. We investigated the correlation between nest defense and egg recognition behavior in Brown-breasted Bulbuls (Pycnonotus xanthorrhous) by conducting dummy and artificial-parasitism experiments. Our results illustrate that in Brown-breasted Bulbuls, rejecters of parasite eggs were more aggressive toward a cuckoo dummy than acceptors, which was opposite to the results of a previous study. We discuss the possible explanations for consistent and antagonistic defenses at the individual level of hosts and suggest that accumulated experience, sufficient to recognize harmful objects, may account for our results in Brown-breasted Bulbuls.