**Description:** A common breeding warbler; males are deep blue with a black face while females are plain olive-green.
**Size & Weight:** 4.3–5.1 inches long. Weighs roughly 0.3–0.4 oz.
**Sexual Dimorphism:** Extreme. Males are blue, black, and white; females are olive-green with a small white "handkerchief" spot on the wing.
**Behavior:** Nests in thick shrubs like mountain laurel. The song is a slow, buzzy "beer-beer-beer-BEEEE."
**Habitat:** Mature hardwood forests and cool hemlock ravines with a dense understory.