Do Parental Feeding Rate and Feeding Synchrony Affect Nest Survival in a Songbird?

Abstract

Nest predation risk is an important factor that may promote the evolution of adaptive parental reproductive strategies in animals. In altricial birds, where parents feed their offspring at the nest for a period of time, parent birds must balance the benefit from increased nest visits and the cost from increased nest predation resulting from their nest visits being detected by predators. Empirical evidence has shown a relationship between parental nest visits and nest predation risks, and parents have been found to be able to reduce the chance of being detected by predators by synchronizing their feeding visits while maintaining feeding rate unchanged. However, it remains poorly understood whether the relationships are universal to all species. We investigated whether nest survival is correlated with parental feeding rate and feeding synchrony in the silver-throated tit (Aegithalos glaucogularis), a songbird endemic to China. We found that parental feeding rate varied by brood size, nestling age and the time during the day, but feeding synchrony was unrelated to the above factors. Moreover, we showed no effect of parental feeding rate or synchrony on nest survival. The failure to find a relationship between parental feeding synchrony and nest survival seems exceptional because it is contrary to findings of previous studies. While there was likely a publication bias regarding previous studies, it is also possible that the evolution of feeding synchrony in different species has different explanations, or the complexity of the predator community and other factors affecting nest survival need to be considered in the analyses.