Community Composition
The overarching composition of Kirtland’s Warbler microbiota is consistent with that of most wild bird surveys to date, with members of Phyla Bacteroidetes, Firmicutes, Proteobacteria, and Actinobacteria comprising the majority of all bacteria detected (Dewar et al. 2014; Lewis et al. 2016; Grond et al. 2018). However, the relative abundances of all phyla changed, sometimes dramatically, as the birds migrated from The Bahamas to Michigan and over time in Michigan. Variation across the annual cycle may reflect difference in presence or abundance of environmental bacteria, responses to altered diets that in turn favor some bacteria over others or vary with host characteristics and requirements. Below, we consider plausible examples of each.