Brilliant sky-blue warbler of the high canopy. Prefers mature deciduous forest, either in riparian areas, or dry mountain ridge-tops. Tends to stay high in the canopy; thus, can be difficult to see blue color. From below, look for white throat and belly, thin necklace, and dark streaks on sides. Female is a unique muted turquoise with pale eyebrow and blurry streaks on sides. Immature birds show yellow wash on underparts. All plumages have bold white wingbars. Easiest to detect by its loud buzzy song, similar to Black-throated Blue but usually richer and more distinctly three-parted; much lower-pitched than Blackburnian Warbler.