Common in large, damp deciduous trees with lichens or spanish moss. Strikingly small and fat with a short, narrow tail. One of the commoner warblers on migration, and a great bird to know well. It belts out its buzzy song, invariably from the top branches. ID: Fat and pot-bellied with a short, narrow tail. NAWA is most similar but lacks neckless and often pointed-headed look of NOPA. Yellow breast and throat always stand out on otherwise white underparts; then check the tail with white bordered by black. Short, broad, often triangular wing bars are the stand-out on the variably blue-and-green upperparts. Head pattern is also distinctive: pale eyelids on a blue head. Ad ♂: brightest with variable rufous-and-black breast band. Ad ♀/imm ♂: limited rufous breast band. Imm ♀: dullest and most uniform. In flight, look at size, shape, wing bar shape, and eyelids.