Abstract <p>Microbiota can both influence or be influenced by social structure and interactions between individual hosts. The use of social network analyses to test for associations between social structure and microbial diversity has only been applied to a few host species. Such an approach could help to disentangle conflicting findings on the effect of social transmission of microbial communities. Here, we explored the following hypotheses: i) that the social network centrality of hosts increases bacterial diversity (alpha diversity), ii) that the strength of social associations between hosts or iii) roosting in the same locations increases microbiota similarity between individuals (beta diversity). For this, we investigated cloaca- and feather-associated microbiotas of wild-caught common waxbills living in a semi-natural environment. We found no evidence for influences of sociality or roosting location on bacterial alpha or beta diversities. We nonetheless detected differences between birds roosting primarily indoors or outdoors at the amplicon sequence variant (for 16S rRNA) and genus levels of feather bacteria, with the birds roosting primarily outdoors having a higher prevalence and abundance of taxa associated with vegetation and the environment, while birds roosting indoors had a higher prevalence and abundance of some bacteria reported as animal-associated. The absence of major effects of host social network on microbiota suggests that environmental effects and individual host idiosyncrasy, perhaps mediated by genetic factors, are more important than within-group sociality driving microbial variation in common waxbills. These results thus call for research on hosts’ genetic diversity and how it may influence their microbiota.</p> Significance statement <p>The social structure of gregarious animals may influence the similarity and diversity of their microbiota. Social proximity between hosts may lead to more similar microbiota, and centrality in the host social network may contribute to more diverse microbiota. Despite these expectations, we found no effects of social structure on microbial diversity in a flock of wild common waxbills sharing an open-air mesocosm environment. We found indications that roosting outdoors made waxbills more prone to host environment-associated bacteria and roosting indoors to animal-associated bacteria. The absence of major effects of social structure on the microbiome suggests that, even in gregarious species, environmental factors and individual host idiosyncrasies, perhaps genetic-based, can be the most important for understanding microbial variation.</p>