Research on the Black-throated Blue Warbler at Hubbard Brook and in Jamaica has been funded largely by research grants from the U.S. National Science Foundation, along with support from our home institutions. The Northern Research Station of the U.S. Forest Service gave permission to conduct research at Hubbard Brook and facilitated the field work there. For the research in Jamaica, we greatly appreciate the help and hospitality of P. Williams, R. and A. Sutton, T. Clarke, E. Zaidie, and Y. Strong. We thank the many colleagues, students and field assistants who have participated in the field work over the last 49 years, including Frank Sturges, Tom Sherry, Len Reitsma, Ben Steele, Pam Hunt, Pete Marra, Gabe Colbeck, Scott Schwenk, Mason Cline, Andrea Townsend, Nina Lany, Michael Hallworth, and Nicole Krauss. The following individuals kindly contributed unpublished information which greatly enhanced this and earlier revisions of the account: I. Lovette on phylogenetic relationships, G. Colbeck and D. Hof on song, and Kim Hall on populations in Michigan. This research is a contribution of the Hubbard Brook Ecosystem Study, part of the Long-Term Ecological Research (LTER) network supported by the U.S. National Science Foundation. The Hubbard Brook Experimental Forest is operated and maintained by the USDA Forest Service, Northern Research Station, Newtown Square, Pennsylvania, USA.