Yes, I have used muzzleloaders for bird hunting on many occasions. Unless you are shooting driven game or on fast waterfowl or dove action (or hunting with extremely impatient partners) the loading time is a non-issue.
As already stated use real black powder unless it is absolutely impossible for you to find. My favorite woodcock, snipe, and partridge gun pictured below is a 17 ga. The load that I have found that works best in this gun, and others I own, is 2 1/2 drams (about 68 grains) of
FFg. One 1/8" nitro card, one 1/8" hard felt wad that I lube with bees wax and tallow. One thin over shot card on top of the lubed wad (to prevent shot from sticking to the lubed wad). 1 oz of shot. Lastly an overshot card.
I load the first three wads at the muzzle after pouring the powder, and ram all three down together with one motion. Then pour the shot, followed with the over shot card. With a little practice you should easily be able to load in 30-40 seconds.
You may find it beneficial to notch the edges of your overshot cards to prevent air pressure build up while ramming them down.
With this load the gun throws a very even cylinder pattern out to 25 yards.
Many shooters use a thick 1/2" lubed wad on top of the nitro card, but I have found in my guns the thinner 1/8" lubed wad patterns much better.
Even after shooting many dozens of shots in a session, the thought of cleaning doesn't even come into the equation until the day is done.