Trill rate dialects in the Rufous-collared Sparrow, Zonotrichia capensis, in northwestern Argentina

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Abstract
Geographical variation in trill rate of Zonotrichia capensis was assessed in a sample of about 2300 individuals from nearly 600 sites distributed throughout northwestern Argentina, from 22 to 34°S. The variation was partitioned among the following site characteristics: original (natural) vegetation, contemporary vegetation structure, latitude, longitude, and altitude. About 45% of the variation was attributable to the original vegetation (p < 0.0001): the other site characteristics explained a further 4%. Thus the geographical distribution of trill rate closely paralleled that of the natural vegetation, even where this vegetation has been long (80–200 years) replaced by various forms of agriculture. These results were interpreted as the consequence of vocal learning influenced by the vocalizations of dominant elements in the local avifauna of each habitat, together with factors affecting the unambiguous propagation of acoustic signals through given kinds of vegetation.