I understand that it is not lawful to take Upland Game Birds from any type of watercraft (which btw is not defined in the regulations so its confusing whether you can be standing in a moored boat or drifting naturally, etc).
I am trying to confirm that Doves are NOT considered Upland Game and are Migratory Birds and allowed to be hunted from watercraft. Is that the case?
Mourning doves are migratory game birds. As a result, federal regulations apply. The corresponding regulation states:
No persons shall take migratory game birds from or by means of any motorboat or other craft having a motor attached, or any sailboat, unless the motor has been completely shut off and/or the sails furled, and its progress therefrom has ceased: Provided, That a craft under power may be used to retrieve dead or crippled birds; however, crippled birds may not be shot from such craft under power.
Federal regulations can be found in Title 50, Code of Federal Regulations, Part 20, which are available at: http://www.gpo.gov/fdsys/pkg/CFR-2008-title50-vol1/content-detail.html.