Housekeeping by lodgers: the importance of bird nest fauna on offspring condition

Abstract

Bird nests are designed to contain and protect parents, eggs and nestlings and to facilitate optimal safety and climatic conditions from egg-laying to fledging offspring. Bird nests also provide optimal conditions for a rich and diverse community of mainly invertebrates, who use nests as a foraging site, shelter, hiding place and reproduction and overwintering site. So far, no study has experimentally examined the impact of other nest inhabitants, except for parasites, on nestling development. The aim of this study was to investigate the impact of a saprophagous fly larvae Fannia spp. on nestling European Bee-eaters (Merops apiaster). We hypothesize that, if Fannia spp. larvae improve nest sanitation due to their detritivorous habits, increased larvae abundance would result in improved chick growth and health. Thus, to investigate the impact of Fannia spp. larvae on nestling Bee-eaters, we experimentally manipulated their abundance during the early nestling period and determined parameters indicative for nestling body condition and health. The experiment confirmed our prediction and revealed that increasing the number of saprophagous fly larvae had a positive effect on offspring condition. We suggest that bird nest fauna other than parasites might be as important and could be used as a model for ecosystem analyses. Bird nests usually constitute small, temporary ecosystems, which could facilitate investigation of aspects of ecosystem functioning.