Commensal
Eating the same food as another animal. Birds which raid crop fields, such as Woodpigeons Columba palumbus, are partly commensal with man. An animal whose whole life depends on another is a parasite, while one which obtains food simply as a result of the activities of another is practising autolycism.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver