Two books I have gathering dust on the book shelf are Making Decoys The Century- Way by Grayson Chesser and Decoys The Art of the Wooden Bird by Richard LeMaster
They both look to be good books with patterns but what do I know for some one who hasn't attempted a decoy carving in 45 or 50 years.
Being on this site however has inspired me and I have some wood curing, who knows what will happen.
Good luck on your quest. Let the chips fly.