The haematozoan parasites of Common Blackbirds Turdus merula: associations with host condition

A population of European Blackbirds Turdus merula was studied to investigate the relationships between blood parasitism and host morphometrics, a putative sexually-selected trait, and reproductive parameters. The prevalence of haematozoa was extremely high and infection was negatively associated with adult morphometrics: adults infected with Leucocytozoon were in relatively poor body condition and had shorter wings than uninfected birds. There was also a negative relationship between blood parasite infection and traits associated with reproduction. The bill colour of males (a putative sexually-selected trait) infected with Plasmodium was duller than that of uninfected males, and in females Haemoproteus infection was significantly positively associated with bill colouration. Haematozoan infection was unrelated to reproductive parameters, and there was no relationship between blood parasite infection and the provision of parental care