A small raptor of foothill forest that favors exposed branches on emergent trees, often near rivers. Black above with a bluish sheen and a black base to the undertail that extends to the thighs and sides. The rest of the underparts are white, extending to the white cheeks. Unmistakable, as there are no other raptors of this size or birds with this color scheme. Voice is a descending, mouse-like squeak, “wiiuuu!”