For instance, Woodpeckers' favorites are suet and nuts; but they will experiment with berries. Tufted Titmice will try nut pieces. Wrens often experiment with suet. Robins will try millet.
If you put a variety of foods out in your landscape, there's no telling what birds will stop by, but you are likely to have something for everyone.
The smallest bird in the world? The Bee Hummingbird lives in the Sierra Maestra Mountains of Cuba. It actually is about the size of a bee. This same forest is said to be home to a close cousin of the elusive Ivory-billed Woodpecker, which was re-discovered living in an Arkansas wetlands.