Bird encounters can be a problem in soaring, because the soaring bird species use thermals the same way we do. Opinions differ on how to deal with it. I've often heard "Don't try to avoid, because the bird is better at it than you are and you'll just screw it up" -- but the one time I put that into practice, it didn't work. I wound up having to punch hard.
If you join a bird in a thermal and circle in the same direction, he'll generally do a good job of maintaining separation; if you circle the other way, he'll write you off as a dummy and go elsewhere.