There are a few birds that begin with the letter D. How about the Downy Woodpecker?

Dove, Mourning
The Mourning Dove, or Zenaida macroura, is a bird common throughout much of North America. This largish bird is usually around a foot long and eats seeds by pecking at the ground. It likes to travel in small flocks.

Duck, Mallard
One of the most common birds in North America, the Mallard Duck is found in just about every pond and stream from coast to coast.

Duck, Muscovy
The Muscovy Duck is also known as the Red Face Duck because of the bright red bands of red that run from its beak to its eyes.

Downy Woodpecker
The Downy Woodpecker, Picoides pubescens, is a cute little woodpecker that loves suet feeders and even sunflower seeds. A common sight at many backyard feeders, it is around 9.5" long with a short beak, white body, and black wings with white stripes.