Increased exposure to parasites and other pathogens is one of the principal costs of group living, and animals have evolved diverse behavioral adaptations to detect and avoid parasitized conspecifics. In mammals, it is well established that parasitic infection can affect host body odor and that individuals use this chemical information in mate choice and other social contexts. In birds, despite intense interest in condition-dependent sexually selected displays as indicators of health status, chemical signaling of infection status remains largely unexplored. However, compounds in feather preen oil are increasingly recognized as candidate substances that may mediate chemical signaling in birds. We inoculated Song Sparrows (Melospiza melodia) with hemosporidian parasites (Plasmodium sp.) to determine whether parasitic infection alters the chemical composition of preen oil. We used gas chromatography with flame ionization detection (GC-FID) to separate and quantify the wax esters in preen oil and compared the chemical profiles of preen oil before inoculation to chemical profiles 13 days later (corresponding to peak infection intensity among the subset of birds that became acutely infected). Inoculation with Plasmodium sp. altered the wax ester profiles of preen oil, albeit with a modest effect size, regardless of whether individuals became acutely infected or resisted the infection. By contrast, wax ester profiles of preen oil were not significantly altered in individuals that received a sham inoculation with uninfected blood. Provided that birds can perceive these alterations in wax ester profiles of preen oil (e.g., after their degradation and release as volatiles), our findings suggest that chemical cues inherent in the wax esters may signal malarial infection status and/or exposure history.
Vol. 135 • No. 3
Vol. 135 • No. 3