1 The movement of individuals or their propagules (seeds, spores, larvae, etc.) from one area to another. Three cases may be distinguished: (a) emigration, which is outward only; (b) immigration, which is inward only; and (c) migration, which in this stricter sense implies periodic movements to and from a given area and usually along well-defined routes. Such migratory movement is triggered by seasonal or other periodic factors (e.g. changing day-length), and occurs in many animal groups.
2 In plant succession, specifically the arrival of migrating propagules (migrules) at a newly denuded area.