The Nearctic-Neotropical migration system

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Blackpoll Warbler Dendroica striata, a Nearctic-Neotropical migrant that migrates over the Western Atlantic

Chapter 25

The Nearctic-Neotropical migration system Approximately half of all neotropical migrants winter in Mexico and the Antilles . . . . relative to the size of the breeding ground, this is a very restricted area. Populations are consequently highly compressed. (John Terborgh 1989.) The New World migration system differs from the Eurasian-African one in several respects. First, the presence of a land bridge between North and South America and of sizeable islands in the Caribbean mean that the journey is potentially far less arduous than for the Old World migrants which must cross large areas of hostile desert or sea. The continuum of habitable ground from North through Central to South America means that there is no large geographical break between potential breeding and wintering areas, which for many species are contiguous or overlapping. Moreover, in the New World, the mountain chains run mainly north-south, rather than east-west, and thus present less of an obstacle to the passage of birds. Second, most of the North American migrants winter