DISCUSSION
Gut microbiota of Kirtland’s Warblers change as individuals and populations migrate from the wintering grounds in The Bahamas to breeding territories in Michigan. Repeated sampling at multiple points across the annual cycle was only possible because we were able to capture, sample, and radio-tag individuals on the wintering grounds and then use automated telemetry to relocate the same individuals thousands of kilometers away on the breeding grounds (Cooper and Marra 2020). Through the resampling of individuals we remove potential biases associated with sampling multiple populations. Therefore, the effects observed can be attributed to true changes within individuals and our study population. We found that period within the annual cycle exerts a notable effect on the overall diversity of the microbiome and birds on their wintering grounds have a significantly different and more diverse community of gut microbiota than those on their breeding grounds. We also identified a common, core microbial profile of Kirtland’s Warbler that persisted throughout multiple portions of the annual cycle.