American Cocker Spaniels are the smallest of the sporting breeds, even though they are small, they can retreive a large bird such as a pheasant, 

Cockers are great flushers, and  also great retreivers, they can mark a long distance fall and make the retreive.  When introduced to water as a young pup they are excellent swimmers as well.

Cockers can hunt in areas many dogs can't because of thier small size to flush out game.