The Collaborative International Dictionary of English v.0.48:

Downy woodpecker \Down"y wood"peck*er\ (-[y^]), n. (Zool.)
   A small black and white ladder-backed woodpecker (Picoides
   pubescens) of Central and Eastern U. S. and Canada. It
   strongly resembles the hairy woodpecker, but is smaller (6
   1/2"), compared with about 9-1/2" for the hairy. It is common
   in suburban backyards.
   [PJC]