I have an assortment of Whiting (Hebert-Miner) capes that are stored in their original zip-lock style poly baggies. When I take them out of their bags they are fine with no oily feel to the skin. BUT the bags themselves are very ouly and are sticking together. Is this the plastic itself degrading or does the plastic somehow draw the oil from the bird skin and let it migrate to the surface? I've never had this happen with other capes that I've had stored for years.