Ardea
Official journal of the Netherlands Ornithologists' Union

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Rappole J.H. (2005) Evolution of old and new world migration systems: a response to Bell. ARDEA 93 (1): 125-131
In Rappole & Jones (2002), a hypothesis was presented explaining how migration between temperate and tropical regions could have evolved from normal dispersal of tropical-breeding resident birds, citing taxonomic, ecological, biogeographic, physiological, and behavioral evidence in support of the theory. In addition, contrasts were made between Old and New World migration systems, e.g., the relative absence of long-distance migrants from European forests, and an explanation was provided for how these differences could have developed given a tropical origin for most temperate migrants. Bell (2005 - this issue) has presented a detailed critique of this hypothesis in which he dismisses much of the reasoning and evidence for the theory, and proposes an alternative "northern home" theory in which migration derives from gradual genetic change in dispersal direction and distance favored by an environmental gradient, presumably climatic deterioration on temperate, breeding grounds. Herein a response is provided to Bell`s critique, clarifying our arguments where they appear to have been misunderstood, and providing additional information in support of ideas on tropical origin for many migratory bird species.


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