It is perfectly legal for waterfowlers who are also fly tiers to use feathers from birds they have harvested.
Feathers from drake wood ducks, mallards, and green-winged teal are the most popular, primarily due to their coloration and abundance. The “lemon” flank feathers from a wood duck are prized for their color and barring. A mallard’s “cul de canard” feathers are sought after for their buoyancy.
LINK (via Ducks Unlimited)