Duck

s are a water dwelling animal found in Red Dead Redemption. Like all animals in the game they can be hunted for sport or for profit.

Locations
The river on the border of America and Mexico.
 * Ducks are also located near the Don Julio Lake, and are generally flying, so let loose on anything thats above you!
 * During the stranger mission Remember My Family you can find ducks at the lake where you finish the mission.

Achievement
The player must kill a duck to successfully complete the following achievement:
 * Unnatural Selection: Kill one of every animal species in the game in any game mode.

http://www.youtube.com/watch?v=dQ9YPl8IGeI