By Tom UhlenbrockMissouri State ParksNorth America???s greatest wildlife migration is underway ??? and Missouri is smack dab in the middle of it.Millions of ducks, geese, swans, pelicans and other waterfowl are on their annual trek to warmer climes for winter, generally along four major flyways that go north to south across the continent ??? the Atlantic, Mississippi, Central and Pacific flyways.