Microgeographic pattern of song variation in the Rufous-collared Sparrow ( Zonotrichia capensis ) in southern Patagonia

Abstract

The Rufous-collared Sparrow (Zonotrichia capensis) presents a complex system of vocal dialects that correlate with vegetation structure in central and northern Argentina. However, the patterns of song variation in the Patagonian subspecies Z. c. australis remain largely unknown. It has been suggested that its songs are atypical, of low amplitude and with very slow trills (or even lacking them entirely) despite living in an open environment. We studied the songs of a southern Patagonian population of this species in Monte León National Park, Argentina. In contrast to reports from northern Patagonia, the songs in this southern locality are typical both in terms of their structure and amplitude, and their trill speed falls within the expected range for open habitat songs for this species. We propose that the differences between the songs of the northern and southern Patagonian populations could be due to the migratory nature of the latter and its resultant exposure to the typical songs of the central and northern Argentine populations during late summer and spring. Our results also uncover a clinal pattern of vocal variation along a transect of 3.5 km from a plateau into an erosion valley, as well as differences with the nearby coast. Variation among the three sites (coast, plateau and valley) includes differences in the speed of the trill and vocal frequencies and may be correlated with an environmental gradient related to wind intensity and also influenced by the surf noise on the coast.