This video shows you how to get the Colonel Sanderson achievement which involves killing a series of chickens. There are certain levels in Modern Warfare 2 that have chicken crates, primarily in the Favela levels. Simply kill several chickens and you should get this achievement.
Call of Duty 4: Modern Warfare 2 is considered one of the best first person shooters of all time. Released for the Xbox360, Playstation 3, and PC, Modern Warfare 2 provides an excellent gaming experience for action lovers. Whether you are new to the game or have completed it on Veteran, there's a good chance you'll find some useful information here.
PS: Don't tell P.E.T.A. we told you about this.