Effects of ectoparasites of young on parents' behaviour in a Mediterraneanpopulation of Blue Tits

In altricial birds, adults are expected to alleviate the impact of parasiti sm on their young by increasing parental care. We experimentally investigat ed the effects of blowfly parasitism on adult behaviour in the nest cavity in a population of Blue Tits in which nestlings are heavily parasitized bgy blowfly larvae. The behaviour of males and females was different, since on ly the females carried out nest sanitation activities related to the presen ce of parasites. The time females devoted to nest sanitation was higher in parasitized nests than in experimentally deparasitized ones, suggesting tha t chicks and adults might share the costs of blowfly parasitism.