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Résumé :
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[1) The number of species of hummingbirds on each West Indian island is correlated with altitude, mainly because montane humid forest brings in an additional species. 2) Each species differs markedly in habitat, feeding stations or size from the others on the same island. In two instances, a species has a wider habitat on islands where another species is absent than on islands where it is present. 3) Probably 9 or 10 mainland hummingbirds have colonised the West Indies. But nearly every mountainous island has only three species, one small, one large lowland and one large montane, and nearly every lowlying island has only two species, one small and one large, presumably as a result of competition for the available ecological resources. 4) Hummingbirds not infrequently wander between the mainland and the islands, and between the islands, so difficulties of dispersal cannot be responsible for the number of species resident on each island. 5) Geographical replacement on different islands is frequent in hummingbird species of similar size and ecology, though they may have minor differences. That such replacement is due to competitive exclusion is indicated particularly by an example within Puerto Rico, without any geographical barrier, and also by the recent replacement of one species by another in the Virgin Islands. 6) Although hummingbirds may move between the islands, and from the mainland, there is a high degree of endemism, presumably due to the rapid evolution of locally adapted forms.]
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