if you are mostly hunting smaller birds (grouse and that kind of thing), then a .410/28-gauge would be best. smaller shotguns are also used for bunnies and squirrels and other smaller animals.

but for ducks or larger, a 12-gauge is generally preferred. a barrel restriction ('choke') allows you to make tighter shots at greater distances.

historically, though, bird-hunters just went ahead and hunted with whatever they owned. you can absolutely hunt ducks with a .410, though you will need to have somewhat better aim (or stick closer to the target) than if you used a larger and more powerful size.

note that weapon selection must be followed by ammunition selection. barrel chokes, for instance, are used to guide diffuse material into a tighter ring. that means birdshot/buckshot or other 'shot.' if you fire a solid round (a 'slug') through a choke, you might destroy your barrel. similarly, if you hunt birds with slugs rather than shot (or use too large shot), you might destroy the birds.

(http://www.autoadmit.com/thread.php?thread_id=5347861&forum_id=2#46370352)

Have you ever hunted before?

For ducks/geese, I like a gas operated 12 ga (like a Browning Maxus 2, Beretta A400, Winchester SX4).

For turkey, a 20 gauge with a pistol grip is the shit.

(http://www.autoadmit.com/thread.php?thread_id=5347861&forum_id=2#46371543)

Taking hunter safety as we speak.

(http://www.autoadmit.com/thread.php?thread_id=5347861&forum_id=2#46372140)