California Code, Fish and Game Code - FGC § 3307

All birds killed or injured by shooters shall be retrieved without delay, and all injured birds shall be humanely dispatched.  The licensee shall not permit injured birds to remain on a pond or feeding area, nor shall he knowingly permit such birds to be used in any subsequent release.

In order to prevent the loss of any dead or injured birds, the licensee shall provide the use of a retrieving dog, without cost, to all shooters, except that shooters may provide their own retrieving dogs.  The licensee shall not permit the shooting of any birds unless a retrieving dog is immediately available for use by all shooters.