Scarlet Tanager

From allaboutbirds.org:

Male Description
Breeding (Alternate) plumage: Bright red all over; variable in hue and can be somewhat orange. Black tail and wings. Whitish bill. Dark eye. Gray legs.
Nonbreeding (Basic) plumage: Bright olive-green body. Black wings and tail. During molts in spring and fall, shows mixed red and olive green in body feathers.

Clearly, this guy is showing his breeding plumage. :)