The cloacal microbiome of a cavity- nesting raptor, the lesser kestrel (Falco naumanni)

Background. Microbial communities are found on any part of animal bodies exposedto the environment, and are particularly prominent in the gut, where they play sucha major role in the host metabolism and physiology to be considered a ``secondgenome''. These communities, collectively known as ``microbiome'', are well studiedin humans and model species, while studies on wild animals have lagged behind. Thisis unfortunate, as different studies suggested the central role of the gut microbiome inshaping the evolutionary trajectories of species and their population dynamics. Amongbird species, only few descriptions of raptor gut microbiomes are available, and mainlycarried out on captive individuals.Objectives. In this study, we aimed at improving the knowledge of raptor microbiomesby providing the first description of the gut microbiome of the lesser kestrel (Falconaumanni), a cavity-nesting raptor.Results. The gut microbiome of the lesser kestrel was dominated by Actinobacteria(83.9%), Proteobacteria (8.6%) and Firmicutes (4.3%). We detected no differencesin microbiome composition between males and females. Furthermore, the generalcomposition of the microbiome appears similar to that of phylogenetically distantcavity-nesting species.Conclusions. Our results broaden the knowledge of raptor gut microbial communitiesand let us hypothesize that the distinct nest environment in terms of microclimateand presence of organic material from previous breeding attempts, to which cavity-nesting species that reuse the nest are exposed, might be an important driver shapingmicrobiomes.