Birds are inhabited by communities of microorganisms, that fulfill beneficial functions for their hosts. Some scientists therefore propose that animals should not be considered as animals, but as meta-organisms – obligate symbiotic life forms of animals with their microorganisms. Until recently, most attention has focused on gut microbes. This project will investigate which microorganisms live in preen glands of birds, and what – through preening of feathers – the contributions are of these microorganisms to the communication between birds and to the antimicrobial protection of their plumage. The investigators expect to find associations between microbial functions and life history strategies of birds.