Eggshell microbiome as a potential microbial reservoir in a cavity nesting bird (Sialia mexicana)

Animals develop microbial associations (i.e., their microbiome) early in life that have been linked to changes in host development, physiology, and survival. However, microbial sources contributing to initial microbial colonization remain unclear. We described a potential microbial source, the eggshell microbiome of Western Bluebirds (Sialia mexicana), a cavity nesting bird. We found bacteria commonly seen in the gut microbiome of other birds, thus, eggshells could represent a source during initial microbial colonization.