Relationships between Blood Parasites, Mating Success and Phenotypic Cues in Male Sage GrouseCentrocercus urophasianus

Abstract

In lek breeding Sage Grouse Centrocercus urophasianus in eastern California, male mating success is strongly correlated with individual differences in lek attendance, and in the rate and acoustic quality of courtship display, suggesting that these provide cues by which females choose mates. Increased lek attendance and high display rates are also associated with elevated metabolic expenditure. This paper examines the hypothesis that the ability to commit energy to display is related to the incidence of blood parasites. A single hematozoan genus, Haemoproteus, was found in 37.5% of 184 Sage Grouse sampled over a five year period. Parasitism varied across years and increased through the breeding season. However, no measure of display performance or mating success was significantly correlated with decreased parasite load among adult males. Several additional lines of evidence, including numerically low infection intensities, the absence of detectable effects of parasites on hematocrit and erythrocyte production, and the seasonal distribution of parasite incidenceall suggested that infections were unlikely to impact male courtship display. Alternative factors maintaining individual variation in male display performance in this population are also evaluated.