Resemblance within flocks and individual differences in feather mite abundance on long-tailed tits, Aegithalos caudatus (L.)

Abstract

Even though feather mites are arthropod ectosymbionts widely distributed on almost all orders of birds, the nature and functional relationship of the interaction between feather mites and birds remain unclear. In this paper, we analyzed factors determining the distribution of feather mites at the individual as well as at the flock level, searching for correlates with bird characteristics such as body size and fat accumulation during winter. Long-tailed tits, Aegithalos caudatus (L.), live in family flocks during winter. Foraging, roosting and territory defence are done in groups. Communal roosting facilitates direct body contact among flock members, which may enhance the transmission of feather mites. Feather mite abundance was more similar within than among flocks. Within flocks, those individuals with longer wings and better body condition as determined by fat scores had larger numbers of feather mites. At the flock level, no relationship was found between mean mite intensity and any of the considered variables. We show that the distribution of feather mites among long-tailed tits is not random, but is shaped by individual features and flock ownership.