Ethological research has revealed that the vocal communications of birds are highly specialized behavioral adaptations that can shed light on evolutionary processes. The calls of the quails of the New World are a good example. This group of birds includes some thirty species, about half of which are limited to the tropical forests of Central and northern South America. The other species are North American, ranging as far north as southern Canada. Morphological evidence favors the view that the most generalized, or “primitive,” of these species are the tree quails of Mexico’s moist mountain forests. The more open-country and arid-adapted species, which extend into the United States. are anatomically more specialized, or “advanced,” and probably were derived from forest-adapted ancestral stock somewhat like the modern tree quails.
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