Stress response, gut microbial diversity, sexual signals, and social interactions in North American barn swallows

Theory predicts that social interactions are dynamically linked to phenotype. Yet because social interactions are difficult to quantify, little is known about the precise details on how interactivity is linked to phenotype. Here we deployed proximity loggers on North American barn swallows (Hirundo rustica erythrogaster) to examine intercorrelations among social interactions, morphology, and features of the phenotype that are sensitive to the social context: stress-induced corticosterone and gut microbial diversity. We analyzed relationships at two spatial scales of interaction: (1) body contact and (2) social interactions occurring between 0.1m and 5m. Network analysis revealed that relationships between social interactions, morphology, corticosterone, and gut microbial diversity varied depending on the sexes of the individuals interacting and the spatial scale of interaction proximity. We found evidence that 1) body contact interactions were related to diversity of socially-transmitted microbes and 2) that looser social interactions were related to signaling traits and corticosterone.