EFFECTS OF PARASITISM BY A HEMATOPHAGOUS MITE ON REPRODUCTION IN THE BARN SWALLOW

Studies the effect of the parasitic haematophagous tropical fowl mite (Ornithonyssus bursa, Macronyssidae, Gamasida) on the reproduction of Hirundo rustica (Hirundinidae). Barn swallows regularly reuse old nests, but avoid old nests with mites. New nests are not primarily infected from old nests harboring large mite populations. Mite population density per nest after fledging was significantly positively related to mite population density on adult swallows upon arrival at the breeding site in early spring the same year. Mate choice may significantly affect levels of ectoparasitism, if parasite loads of nests originate from inoculates provided by adult barn swallows. Addition of mites to nests decreased reproductive success of the birds measured in terms of number of independent fledglings of 1st clutches and in terms of clutch size, brood size, and number of independent fledglings of 2nd clutches. Barn swallow nestlings in nests with mites had lower body mass but similar body size compared with nestlings in pyrethrin-sprayed nests. Incubation periods were longer and nestling periods shorter for nests with added mites. Interclutch intervals were significantly shorter in the group of sprayed nests, mainly because more such nests were reused for 2nd clutches and because adult swallows suffered less from mite infestations. Slightly fewer barn swallows had second clutches during the same breeding season if their nests held many mites. -from Author