Stability and change in vocal dialects of the yellow-naped amazon

Abstract

Cultural evolution is an important force in creating and maintaining behavioral variation in some species. Vocal dialects have provided a useful model for the study of cultural evolution and its interactions with genetic evolution. This study examined the acoustic and geographic changes in vocal dialects over an eleven-year span in the yellow-naped amazon, Amazona auropalliata, in Costa Rica. Contact calls were recorded at 16 communal night roosts in 1994 and 19 roosts in 2005, with 12 roosts sampled in both surveys. In both surveys three dialects were found, each characterized by a distinctive contact call type and each encompassing multiple roosts. The limits between two of these dialects, the North and South dialects, was found to be geographically stable, while at the boundary between the North and Nicaraguan dialect there was introgression of each call type into roosts in the bordering dialect. Acoustic measurements and cross-correlations of spectrograms detected no change in the acoustic structure of contact calls in the South dialect but did show significant differences in the calls of both the North and Nicaraguan dialect between 1994 and 2005. These results are consistent with the vocal convergence hypothesis that proposes that dialects are long-term features maintained through some combination of biased transmission of local call types and purifying selection against foreign call types. Migration, copying errors and cultural drift may also play a role in the more subtle changes seen in the acoustic form of dialect call types.

A test of multiple hypotheses for the function of call sharing in female budgerigars, Melopsittacus undulatus

“…In other species, shared vocalizations develop within groups through social learning of signals; such sharing has been observed in a number of taxa including cetaceans (Smolker and Pepper 1999; Janik 2000; Miller et al 2004; Watwood et al 2004), parrots (Farabaugh and Dooling 1996; Wanker et al 2005; Scarl and Bradbury 2009; Salinas–Melgoza and Wright 2012), songbirds (Mammen and Nowicki 1981; Farabaugh et al 1988; Brown and Farabaugh 1991; Sewall 2009), hummingbirds (Stiles 1979; Yang et al 2007), and bats (Boughman 1997). The sharing of vocal signals can occur at different levels, ranging from the small scale dyadic sharing between two individuals (Wanker et al 2005; Moravec et al 2006; Balsby and Scarl 2008) to large-scale geographic dialects (Baker and Cunningham 1985; Groth 1993; Myasato and Baker 1999; Wright et al 2008; Kershenbaum et al 2012). In addition, sharing can occur via imitation, in which one individual imitates another's call, or convergence, which we define as two or more birds developing new or intermediate vocalizations with aspects of each other's calls.…”

Evidence for Vocal Learning and Limited Dispersal as Dual Mechanisms for Dialect Maintenance in a Parrot

“…As in other dialect systems, there is evidence of temporal and spatial stability [5], stronger response to same dialect breeding territory intrusions [10], and indirect genetic evidence for movement of individuals across dialects [12], [16]. We experimentally simulated dispersal of wild yellow-naped amazons across vocal dialects to evaluate the relative importance of different mechanisms for dialect maintenance.…”

Persistence of song types in Darwin's finches, Geospiza fortis , over four decades

“…Mechanisms favouring the temporal stability of song types include preferences for specific (e.g. local) song types, or selection against songs with divergent acoustic features (songs that feature copy error or innovation or songs from a distant population, Wright et al 2008). In the case of G. fortis, individuals appear not to have a choice of what song to copy; it is that of their social father.…”