Insect predation reduces the abundance of a nidicolous ectoparasite

Abstract

1. Parasites are one of the main actors in host–parasite interactions. Still, their role as a prey and the related consequences for such interactions and in other respects, such as food webs, are frequently overlooked.2. This paper analyses predation pressure on a ubiquitous avian ectoparasitic fly, Carnus hemapterus, identifies their main natural enemies and quantifies their relative effect on the abundance of the parasite. Also, the effect of nest‐site type on their main enemies' predation pressure was analysed.3. Several ant species were found in the nest boxes of the host species, the European roller (Coracias garrulus), during the breeding season and preyed upon adult and larval stages of Carnus.4. Ants were also the putative predators of carnid pupae after the breeding season, when significant reduction (on average, by half) in the abundance of carnid pupae occurred in 75% of nest boxes within few months.5. Carnid pupae are also reported here, for the first time, to be parasitised by the parasitoid wasp Chartocerus conjugalis, whose prevalence was around 21%.6. Nest‐site type had no clear effect on the predation rate of carnid pupae after the breeding season.7. It was concluded that predation is an important factor regulating the abundance of ectoparasites, and thus, it may influence the outcome of host–parasite relationships.