Résumé
Evidence that bird odour can encode social information that can be used in
chemical communication is growing, but is restricted to a few taxonomic
groups. Among birds, diurnal raptors (i.e. birds from the Accipitriformes
and Falconiformes order) have always been considered as mainly relying on
their visual abilities. Although they seem to have a functional sense of
smell, whether their odour can convey social information has yet to be
determined. Combining gas-chromatography-mass-spectrometry (GCMS) and
microsatellite data, we tested whether chemical compounds from preen gland
secretions can encode sex, age, individuality, seasonal differences and
genetic relatedness in the gregarious accipitriform black kite Milvus
migrans. While no differences in preen oil composition were found between
age classes, an individual signature was detected. While a seasonal
variation was found in both sexes, compounds differ between sexes in the
non-breeding season. Finally, a significant correlation between chemical
proximity and genetic proximity was detected in male-male dyads and
male-female dyads but not in female-female dyads. Our study provides the
first evidence in raptors that preen secretion can convey information that
may potentially be used in individual recognition, reproductive
synchronization and inbreeding avoidance, and suggests that raptors may
rely upon their olfactory abilities more than previously thought. This
study opens promising avenues for further studies in raptor chemical
communication.