Emu - Austral Ornithology ISSN: 0158-4197 (Print) 1448-5540 (Online) Journal homepage: http://www.tandfonline.com/loi/temu20 Vocal dialects in parrots: patterns and processes of cultural evolution Timothy F. Wright & Christine R. Dahlin To cite this article: Timothy F. Wright & Christine R. Dahlin (2017): Vocal dialects in parrots: patterns and processes of cultural evolution, Emu - Austral Ornithology To link to this article: http://dx.doi.org/10.1080/01584197.2017.1379356 View supplementary material Published online: 12 Oct 2017. Submit your article to this journal View related articles View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=temu20 Download by: [24.186.124.167] Date: 12 October 2017, At: 19:40 EMU - AUSTRAL ORNITHOLOGY, 2018 https://doi.org/10.1080/01584197.2017.1379356 Vocal dialects in parrots: patterns and processes of cultural evolution Timothy F. Wrighta and Christine R. Dahlinb aDepartment of Biology, New Mexico State University, Las Cruces, NM, USA; bDepartment of Biology, University of Pittsburgh at Johnstown, Johnstown, PA, USA ABSTRACT ARTICLE HISTORY Vocal dialects have fascinated biologists for over 50 years. This mosaic pattern of geographic Received 30 April 2017 variation in learned vocalisations was first described in a songbird, and since that time most Accepted 5 September 2017 studies investigating dialects have focused on songbird species. Here we examine patterns of KEYWORDS geographic variation in the calls of a different group of vocal learning birds, the parrots (order Contact calls; cultural Psittaciformes). We summarise the growing literature on vocal variation in parrots, and comple- evolution; dialect; ment this review with a survey of variation in the genus Amazona using calls from sound libraries. geographic variation; We find strikingly similar patterns to those previously found in songbirds. Over 90% of parrots parrots; Psittaciformes examined in the literature, and 69% of Amazona species surveyed, showed geographic variation consistent with a propensity to share local call types. This trait is evolutionarily labile and widespread; within Amazona most clades contained species with and without geographic varia- tion, and most major lineages of parrots include representatives with dialects. We found little support for the long-standing hypothesis that dialects isolate populations and thus generate genetic differences among populations. Instead, most studies support the idea that dialects are maintained by social benefits of matching local call types, a finding that has implications for the management of captive and endangered populations. Considerable scope remains for studies that experimentally test hypotheses for the exact nature of these benefits, as well as studies that employ comparisons among species, to understand how the interplay between ecology, social dynamics and vocal learning capacities produces different patterns of variation across the parrots. Introduction Since this initial discovery in the White-crowned Sparrow, vocal dialects have been described in many Dialects were first described in animal vocalisations by other songbird species (reviewed in Podos and Warren Marler and Tamura (1962) in their classic study of the 2007) and in representatives of all taxa with the ability White-crowned Sparrow (Zonotrichia leucophrys nut- to learn vocalisations, including parrots (Wright 1996), talli). They found a distinct pattern of mosaic variation hummingbirds (Wiley 1971), bats (Boughman 1997), in the territorial songs of males of this species, such that and cetaceans (Ford 1991). These studies have revealed there was relatively minor variation in acoustic structure Downloaded by [24.186.124.167] at 19:40 12 October 2017 diverse patterns of geographic variation, including of songs among males within populations and distinct some species with classic mosaic dialects with sharp differences in structure among different populations. transitions in structure, some with graded or clinal Marler and Tamura went on to show in a series of elegant variation, and some that lack geographic variation experiments that these songs were acquired by males entirely (e.g. in parrots Wright 1996; Baker 2000; early in life through social learning of the songs of adult Bradbury et al. 2001; Guerra et al. 2008). Even within males, a process they termed ‘cultural transmission’ the subset of species with clear vocal dialects, there is a (Marler and Tamura 1964). They inferred that the dialect wide range of spatial scales over which particular var- variation seen among populations was maintained by iants are shared, ranging from microgeographic varia- cultural transmission of different song types within dif- tion among neighbourhoods composed of a few ferent populations, perhaps coupled with limited disper- territorial males to macrogeographic variation extend- sal between populations (Marler and Tamura 1962). Thus ing over thousands of kilometres (Podos and Warren the dialects of the White-crowned Sparrow appeared to 2007). This variation has led to considerable interest in share many similarities with their namesake dialects in determining what underlying processes lead to the human languages (Cavalli-Sforza 2000). formation of vocal dialects, and what determines the CONTACT Timothy F. Wright [email protected] Supplemental data for this article can be accessed here. © 2017 BirdLife Australia 2 T.F.WRIGHTANDC.R.DAHLIN form and scale of spatial variation within species affect signal transmission, such as the amount of vegeta- (Baker and Cunningham 1985; Handley and Nelson tion, and that acoustic variants would transmit better in 2005; Podos and Warren 2007). Further questions their own habitat than in other habitats. revolve around the degree of the temporal stability of The fourth and final hypothesis suggests that geo- vocal variation, and whether distinctions in geographic graphic variants, in and of themselves, provide no selec- patterns made by humans (e.g. dialects, clinal variation tive advantage. The cultural drift hypothesis proposes or (apparently) invariant vocalisations) are perceived as that geographic variants are simply functionless epiphe- meaningful by the animals themselves. Finally, there nomena that are by-products of learning that occurs has been considerable interest in whether geographic from local models with some degree of copying errors variation in learned vocalisations is associated with, coupled with limited dispersal between populations and perhaps mutually reinforces, neutral genetic varia- (Payne 1981). These processes are predicted to lead to tion among populations (Nottebohm 1972; Baker et al. the accumulation of different variants in different 1982; Baker and Cunningham 1985; MacDougall- regions through a process that has been termed ‘cultural Shackleton and MacDougall-Shackleton 2001; Wright drift’, in analogy to genetic drift of genetically trans- and Wilkinson 2001; Soha et al. 2004; Wright et al. mitted traits. Importantly, cultural drift is not mutually 2005; Lipshutz et al. 2017). exclusive with hypotheses inferring selective advantages; A plethora of hypotheses have been proposed for how for example, dialects might originally form due to isola- dialects are formed and maintained, with overlapping tion and copying errors and then persist through bene- and sometimes confusing terminology (Nottebohm fits associated with sharing vocal variants with 1972;Payne1981; Baker and Cunningham 1985; neighbours within a certain range (Sewall et al. 2016). Handley and Nelson 2005; Podos and Warren 2007). It is also worth noting that discussion about these Here we have divided hypotheses for the formation and processes has been muddied by the fact that dialects maintenance of vocal dialects into four groups represent- themselves are not individual-level phenomena that are ing discrete underlying processes that lead to the sharing subject to evolution by natural selection, but instead are of geographic variants by neighbours; sexual selection, population- or species-level phenomena that arise out of signalling group membership and familiarity, environ- a propensity of individuals to share local variants with mental adaptation, and cultural drift. The first two pro- other individuals. Thus we should not be asking how or cesses are similar in that individuals who adhere to local why dialects evolve, but rather (i) why individuals evolve variants acquire some form of socially advantageous the propensity to share local variants of calls, and (ii) selective advantage. In the sexual selection hypothesis, what other factors interact with this trait to impact geographic variation in vocalisations is driven primarily dialect formation such as the propensity for copying by female preferences for locally specific variants, and errors, the strength of conformation to local types, the individuals with the correct variants are predicted to degree of dispersal, the timing of learning relative to acquire mates with greater success (Podos and Warren dispersal and the stability of the social group. 2007). Geographic variation could result from arbitrary Here we examine patterns of geographic variation in female preferences as females strive to have locally sexy the vocal repertoires of the parrots and cockatoos Downloaded by [24.186.124.167] at 19:40 12 October 2017 sons or could be driven by females’ desire to mate with (order Psittaciformes, hereafter ‘parrots’) with the males with locally adapted