Snood pretty much summed it up. Some trad guys, particularly in the Pacific Northwest and coastal Alaska use goose wing feathers instead of turkey feathers for fletching. How much better it is, I personally don't know. On the birds themselves, again, like he said, they have a "preen gland" which contains oil. It is at the base of tail on the dorsal side. They reach back with their bill, and get the oil and spread it out over their feathers by preening. I'm sure it works well for a while, but periodically needs to be redone in nature, so it also needs to be redone when we are using feathers for fletching.