Nah snows come out of juvie color their first spring. By the time the migration gets here in spring a solid third are in full color with the rest some mix imbetween. This is just a good old fashion interphase. The mixing is getting so strong there are some now that only have a small amount of brown on their back and look completely like snows from underneath. Have one on the wall with coffee can size piece of brown feathers on its shoulders and that's about it other than its wings.