High prevalence of blood parasites in hawfinch Coccothraustes coccothraustes

Fifty-seven hawfinches Coccothraustes coccothraustes were caught in May-June 1982-2001 on the Curonian Spit in the Baltic Sea and investigated by microscopical examination of stained blood films. Haemoproteus fringillae, H. tartakovskyi, Leucocytozoon dubreuili, L. fringillinarum, L. majoris, Plasmodium relictum, P. vaughani, Trypanosoma avium, T. everetti , and microfilariae were identified. The overall prevalence of infection was 100%. Prevalences of Haemoproteus spp. (89.5%), Plasmodium spp. (61.4%), Leucocytozoon spp. (78.9%), Trypanosoma spp. (26.3%), and microfilariae (29.8%) were recorded. No differences were discernible in parasite fauna, prevalence, or intensity of infection between males and females or between young and adult birds. The majority of infections (86.0% of all birds) were mixed, with parasites from two to five different genera present in each blood smear. These birds were failed breeders migrating through the Curonian Spit. It is probable that heavy haematozoan infections can influence the breeding success of birds.