Colonisation
Extension of the breeding distribution of a species by natural means (rather than by introduction). A rapid colonisation of an area is called an invasion. Among recent colonists of Britain are the Savi's Warbler Locustella luscinioides, which was first proved to breed in 1960, and the Cetti's Warbler Cettia cetti, for which breeding was first proved in 1972.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver