Urbanization is a global process with numerous consequences on wildlife, including the amplification of certain infectious diseases. No studies have yet determined if this pattern exists across all detectable pathogenic bacteria, and few have investigated how bacterial communities change across urban to rural/native habitat gradients. We used whole-community sequencing of partial 16S rRNA gene amplicons to examine relationships between urban and rural bacterial communities found on Mountain Chickadee (Poecile gambeli) feathers and nests in Kamloops, British Columbia, Canada. Between urban and rural sites, we observed mostly similar abundances of major bacterial phyla, and dominant genera with pathogenic members, on both bird feathers and their nests. However, urban habitats tended to increase the richness of both bacterial communities and potential pathogens on birds, and accounted for some of the differences in bacterial occurrence between urban and rural environments. Similarities in bacterial communities between nests and their occupants indicated some degree of transmission occurred between them, or that shared environments result in similar community assemblages. We predicted habitat using potential pathogen occurrence with a 90% success rate for feather bacteria, and a 72.2% success rate for nest bacteria, indicating an influence of urban environments on potential pathogen presence. Our findings show that urban environments result in significant differences between urban and rural bacteria associated with Mountain Chickadees, with potential indications towards diverging disease dynamics across urban and rural gradients.
