Increased Vocal Discrimination By Learning in Sympatry in Two Species of Chaffinches

Abstract

Maps of the territories of the two species of chaffinches in an area of sympatry on Tenerife (Fringilla coelebs and F. teydea) show that they are not interspecifically territorial. Playback experiments of heterospecific song show that both species tend to respond in areas of allopatry, but only rarely in sympatry. There is no clear difference in song structure in either species between areas of sympatry and allopatry. Although a comparison of common chaffinch song among 14 samples in the Atlantic region shows significant amounts of differentiation among regions, there is no clear evidence of character displacement. The divergence of blue chaffinch song can best be explained by the withdrawal of hypothesis, whereby naive birds colonized the Canaries before learning their songs from adult tutors, and thus started a new song tradition. The divergence of common chaffinch song in the Atlantic islands seems to have originated independently of the presence of blue chaffinches there. Both species of chaffinches show increased vocal discrimination in areas of local sympatry, pointing to the role oflearning in associating species-specific songs with the morphological phenotypes of male common and blue chaffinches. Although enhanced vocal discrimination via learning can be used to prevent wastage of time and effort in responding to heterospecific song, it cannot have arisen as a consequence of selection for different specific mate recognition systems in these two species of chaffinches.