CONCLUSION
The ability to study the same individuals and populations throughout the
annual cycle greatly enhances our understanding of the consequences of
changing environments and seasonal physiological stressors on gut
microbiota. We demonstrate that a significant compositional shift occurs
in the community structure of gut bacteria as Kirtland’s Warblers
migrate from The Bahamas to Michigan. Additionally, we describe a
species-specific core microbiome and the proportion of bacterial
lineages retained across three periods of the annual cycle within
individuals. Though Kirtland’s Warblers were recently removed from the
endangered species list, continued management and research is needed for
this species to survive. Healthy gut microbiota should be included in
the maintenance of threatened and endangered species (Allan et
al. 2018; Roth et al. 2019; DeCandia et al. 2020) and
this study provides model data as to how species with small population
sizes and extreme habitat specialization react to changing environments.