Individual genetic diversity is predicted to influence host–parasite interactions. Together with the genes directly associated with immune responses, variation in genes regulating vertebrate melanin-based pigmentation may play an important role in these interactions, mainly through the pleiotropic effects that affect colour-specific physiology, behaviour and immunity. Here, we test the hypothesis that the prevalence of avian malarial parasites differs between phenotypes in a raptor species in which the genetic basis of colour polymorphism and its pleiotropic effects over immune functions are known. We found that dark morphs had a higher prevalence of Plasmodium parasites than pale ones but detected no such association for Haemoproteus. This pattern may be associated with unequal exposure to vectors or, as suggested by our circumstantial evidence, to a differential ability to mount an immune response against blood parasites.

Prevalence of blood parasites in Eleonora's falconData on infection status by Plasmodium and Haemoproteus of adult Eleonora’s falcons (Falco eleonorae) from the Canary Islands. The first column (Recaptures) indicates birds that were recaptured in successive years. The year of capture, sex, color morph, body condition and the ring number (ID) of each bird are provided.Dataset.xlsx