Parasite
An organism which entirely depends on another (its 'host') for its livelihood. An ectoparasite lives outside its host's body, while an endoparasite lives inside. Birds suffer from a wide range of both types. In addition the Cuckoo Cuculus canorus is a brood parasite, while the skuas (family Stercorariidae) and the gulls (family Laridae) often practise kleptoparasitism.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver