Carotenoid ornamentation of adult male Common Redpolls predicts probability of dying in a salmonellosis outbreak

Abstract

Summary Conditional handicap models of sexual selection predict that ornamentation should be positively associated with an individual's ability to withstand challenges to their health. We assessed whether levels of carotenoid ornamentation were related to the probability of adult male Common Redpolls, Carduelis flammea, dying in a salmonellosis epidemic by comparing the ornamentation of surviving adult male redpolls to those found dead. Hosts suffering from salmonellosis shed bacteria in faeces, and new individuals are typically infected when they ingest faeces‐contaminated food. The proportion of adult males in the sample of dead birds was significantly higher than in the sample of living birds. Among adult males, probability of survival was significantly predicted by the expression of their carotenoid signals: brightly ornamented adult males were more likely to die in the epidemic. A probable hypothesis for these results is that if carotenoid ornamentation in redpolls functions as a status badge of dominance, bright males would have had priority access to highly preferred, and contaminated, food patches.