Song dialects as barriers to dispersal in white-crowned sparrows, zonotrichia leucophrys nuttalli.

TLDR: No unifying theory exists to explain the diversity of dialect systems, but several workers have suggested that mating probabilities might be influenced by song dialects with the effect of reduced genetic exchange among dialect groups.

Abstract: Studies of avian communication systems have revealed an impressive number of cases in which a bird species exhibits a mosaic pattern of clusters of males singing a song or songs peculiar to each cluster (the most intensive study is that of Baptista, 1975). In some species, these subgroups are discrete, but in other species the differences between subgroups gradually grade from one to another. The geographic dimensions of these so-called dialects may be quite local, a few km 2 (Marler and Tamura, 1962), or more regional, a few hundred km 2 (Nottebohm, 1969). No unifying theory exists to explain the diversity of dialect systems, but several workers have suggested that mating probabilities might be influenced by song dialects with the effect of reduced genetic exchange among dialect groups (Nottebohn, 1969; Baptista, 1975). In the few species carefully studied, it has been found that the song dialect is learned early in ontogeny (Marler and Tamura, 1964; Mundinger, 1975). The dialect phenomenon suggests two kinds of questions. First, how do song dialects originate? One view of the historical origin of a dialect system is analogous to a sympatric speciation model in which dialects arise within a continuously distributed population with the passage of time (Nottebohm, 1969). An alternative proposal, essentially an allopatric model, is that dialects arise from a colonization or