Female barn owls (Tyto alba) advertise good genes

The good genes hypothesis of sexual selection postulates that ornamentation signals superior genetic quality to potential mates. Support for this hypo thesis comes from studies on male ornamentation only, while it remains to b e shown that female ornamentation may signal genetic quality as well. Femal e barn owls (Tyto alba) display more black spots on their plumage than male s. The expression of this plumage trait has a genetic basis and it has been suggested that males prefer to mate with females displaying more black spo ts. Given the role of parasites in the evolution of sexually selected trait s and of the immune system in parasite resistance, we hypothesize that the extent of female plumage 'spottiness' reflects immunological defence. We as sessed the genetic variation in specific antibody production against a non- pathogenic antigen among cross-fostered nestlings and studied its covariati on with the plumage spottiness of genetic parents. The magnitude of the ant ibody response was positively correlated with the plumage spottiness of the genetic mother but not of the genetic father. Our study thereby provides t he first experimental support, to our knowledge, for the hypothesis that fe male ornamentation signals genetic quality.