Hybridisation
Interbreeding involving individuals of different species. Only related species can hybridise and hybrids tend to be incapable of reproduction. They are usually at a disadvantage in the struggle for survival as natural selection tends to operate against them. Therefore, hybridisation is undesirable and is seldom found in the wild among most groups of birds, various types of isolating mechanism preventing mistakes being made.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver