Song Dialects Research Articles

Song and genetic divergence within a subspecies of white-crowned sparrow (Zonotrichia leucophrys nuttalli).

Animal culture evolves alongside genomes, and the two modes of inheritance-culture and genes-interact in myriad ways. For example, stable geographic variation in culture can act as a reproductive barrier, thereby facilitating genetic divergence between "cultural populations." White-crowned sparrows (Zonotrichia leucophrys) are a well-established model species for bird song learning and cultural evolution, as they have distinct, geographically discrete, and culturally transmitted song types (i.e., song dialects). In this study, we tested the hypothesis that divergence between culturally transmitted songs drives genetic divergence within Nuttall's white-crowned sparrows (Z. l. nuttalli). In accordance with sexual selection theory, we hypothesized that cultural divergence between mating signals both preceded and generated genetic divergence. We characterized the population structure and song variation in the subspecies and found two genetically differentiated populations whose boundary coincides with a major song boundary at Monterey Bay, California. We then conducted a song playback experiment that demonstrated males discriminate between songs based on their degree of divergence from their local dialect. These results support the idea that discrimination against non-local songs is driving genetic divergence between the northern and southern populations. Altogether, this study provides evidence that culturally transmitted bird songs can act as the foundation for speciation by sexual selection.

Familiarity and homogeneity affect the discrimination of a song dialect

Familiarity and homogeneity affect the discrimination of a song dialect

Using culturally transmitted behavior to help delineate conservation units for species at risk

Culture (information or behavior acquired by social learning and shared by members of a community) is an inheritance system that that can contribute to the designation of conservation units for species at risk. The phenotypic diversity produced by culture is of intrinsic value and behaviorally-cohesive communities or sets of communities may be suitable candidate conservation units. This paper considers how cultural information can contribute to the designation of conservation units, in particular when assessing the discreteness and/or evolutionarily significance of potential units. Call and song dialects are particularly useful for documenting discreteness, while differences in seasonal migrations, if consistent, can be evolutionarily significant. Distinctions in foraging behavior or diet can suggest discreteness and/or evolutionary significance but it is important to show these are not environmentally driven. Social and play behavior can also be used to show discreteness. In some cases, it may not be clear whether behavioral differences are genetically or culturally determined but this may not matter for the delineation of conservation units if the behavioral distinctions are heritable. Genetic correlations can indicate the stability of culturally-determined behavior when transmission processes are parallel (e.g., mitochondrial DNA and behavior learned from the mother). The explicit use of cultural data in the delineation of conservation units is currently rare, but should increase as more detailed and extensive behavioral databases are compiled and analytical methods are developed.

Using song dialects to reveal migratory patterns of Ruby-crowned Kinglet populations

Using song dialects to reveal migratory patterns of Ruby-crowned Kinglet populations

Local and range-wide distribution of song types suggest Ovenbirds (Seiurus aurocapilla) have song neighborhoods but not macro-dialects

The song systems of oscine passerines (songbirds) are complex and diverse. Because songs are used for both mate attraction and territory defense and are therefore important signals for survival and reproduction, comprehensive knowledge of within and among species song structure and distribution is informative for understanding the evolution of song repertoires and vocal behaviour. In this study, we explored variation in the song structure of the Ovenbird (Seiurus aurocapilla), a widespread warbler (Family Parulidae) found in North American forests. We analyzed recordings from the 2021 breeding season to assess song type variation at a local (n ​= ​158 birds; Sault Ste. Marie, ON) and breeding range scale (n ​= ​512 birds; eBird). We characterized the local song types and tested whether Ovenbirds share song types with their neighbors more often than expected by chance. We then characterized song types of Ovenbirds across the breeding range to determine whether any geographic pattern of song clustering exists (i.e., macro-dialects). We found 10 distinct song types and some evidence for song type clustering at the local study site (i.e., song neighborhoods). We found 7 of those 10 song types throughout the breeding range and identified an additional 24 types that were not recorded in our local population. We found no evidence for song dialects across the Ovenbird breeding range. This study contributes to our understanding of Ovenbird song while simultaneously adding to our understanding of geographic structuring of warbler repertoires. Our work contributes to delineating a more comprehensive understanding of factors affecting dialect development for this diverse group of songbirds.

Species-specific song responses emerge as a by-product of tuning to the local dialect

Oscine birds preferentially respond to certain sounds over others from an early age, which focuses subsequent learning onto sexually relevant songs.1,2,3 Songs vary both across species and, due to cultural evolution, among populations of the same species. As a result, early song responses are expected to be shaped by selection both to avoid the fitness costs of cross-species learning4 and to promote learning of population-typical songs.5 These sources of selection are not mutually exclusive but can result in distinct geographic patterns of song responses in juvenile birds: if the risks of interspecific mating are the main driver of early song discrimination, then discrimination should be strongest where closely related species co-occur.4 In contrast, if early discrimination primarily facilitates learning local songs, then it should be tuned to songs typical of the local dialect.5,6,7 Here, we experimentally assess the drivers of song discrimination in nestling pied flycatchers (Ficedula hypoleuca). We first demonstrate that early discrimination against the songs of the closely related collared flycatcher (F.albicollis) is not strongly affected by co-occurrence. Second, across six European populations, we show that nestlings' early song responses are tuned to their local song dialect and that responses to the songs of collared flycatchers are similarly weak as to those of other conspecific dialects. Taken together, these findings provide clear experimental support for the hypothesis that cultural evolution, in conjunction with associated learning predispositions, drives the emergence of pre-mating reproductive barriers.

Microgeographical variation in birdsong: Savannah sparrows exhibit microdialects in an island population

Social communication often involves vocal learning, whereby young animals learn their vocalizations early in life by imitating the sounds of adults. In animals that learn their vocalizations, it is common to find patterns of geographical variation known as ‘vocal dialects’, acoustic features shared within a cluster of animals that differ from the vocalizations of animals in nearby clusters. Dialects may form when animals learn their vocalizations early in life and then disperse short distances, or when they modify their vocalizations to match local vocal patterns after dispersal. Dialects are typically studied at a regional or continental scale, but they may also persist at smaller scales in so-called ‘microgeographical song dialects’ or ‘microdialects’. Microdialects have received little research attention. In this study, we investigate microdialects and dispersal distance in song-learning Savannah sparrows, Passerculus sandwichensis, through a 4-year study of birds living on three islands in the Bay of Fundy, Canada. Our analyses yield evidence of microgeographical variation: birds showed higher acoustic similarity to their neighbours than to faraway individuals in the same population. When we classified songs on the basis of their highly variable middle sections, we found that particular song types formed spatial clusters of similar-sounding individuals. Therefore, acoustic variation in Savannah sparrow song appears to show dialects across small geographical distances. In an analysis of dispersal from natal sites to breeding sites, we found a median distance of 189 m, consistent with previous findings. Our results suggest that limited dispersal distances, combined with the social processes of vocal learning (overproduction and selective attrition), likely contribute to the presence of microdialects.

Song as a signal of male identity and quality in the Green-winged Saltator (Saltator similis)

Birdsong is commonly associated with sexual selection. It can influence mate choice through honestly signaling the emitter's quality. Such quality may be reflected, among other factors, in body condition and bite force. The Green-winged Saltator (Saltator similis) is a good model species to assess such relationships because males defend their territories throughout the year and sing a stereotyped song, which is known to be associated with sexual selection. The objective of this work is to assess the relationships among song structure, vocal individuality, and possible fitness indicators (body condition, morphology, and bite force) in captive male Green-winged Saltators. We conducted a linear discriminant analysis (LDA) to assess vocal individuality and to highlight the principal acoustic variables associated with it. We conducted Y-Aware PCAs to evaluate the relationship between the body condition index, bite force, and morphometric and bioacoustic variables. The morphometric variables, particularly head width and length, explained 23% of the bite force variation. The acoustic variation explained 36.17% of body condition index variation, but a small nonsignificant amount of bite force (12%). From the acoustic variables, peak frequency and high frequency of the last syllable, slope of the first syllable, and emission rate showed significant negative relationships with body condition. The LDA model based on acoustic variables had a 97.47% accuracy, although this result might also reflect regional song dialects. The acoustic variables most relevant to individual classification (first syllable duration, last syllable duration, whole-song slope, and whole-song duration) are not the same variables that had a stronger relationship to body condition. Besides that, there can be a weaker mixed signaling, as variables related to frequency modulations were important in both contexts. Our results suggest that the song may act as an honest signal of an individual's body condition in this species.

Machine learning reveals cryptic dialects that explain mate choice in a songbird

Culturally transmitted communication signals – such as human language or bird song – can change over time through cultural drift, and the resulting dialects may consequently enhance the separation of populations. However, the emergence of song dialects has been considered unlikely when songs are highly individual-specific, as in the zebra finch (Taeniopygia guttata). Here we show that machine learning can nevertheless distinguish the songs from multiple captive zebra finch populations with remarkable precision, and that ‘cryptic song dialects’ predict strong assortative mating in this species. We examine mating patterns across three consecutive generations using captive populations that have evolved in isolation for about 100 generations. We cross-fostered eggs within and between these populations and used an automated barcode tracking system to quantify social interactions. We find that females preferentially pair with males whose song resembles that of the females’ adolescent peers. Our study shows evidence that in zebra finches, a model species for song learning, individuals are sensitive to differences in song that have hitherto remained unnoticed by researchers.

Regional song dialects of the Ruby-crowned Kinglet

Regional song dialects of the Ruby-crowned Kinglet

Fitness costs of female choosiness are low in a socially monogamous songbird.

Female mate choice is thought to be responsible for the evolution of many extravagant male ornaments and displays, but the costs of being too selective may hinder the evolution of choosiness. Selection against choosiness may be particularly strong in socially monogamous mating systems, because females may end up without a partner and forego reproduction, especially when many females prefer the same few partners (frequency-dependent selection). Here, we quantify the fitness costs of having mating preferences that are difficult to satisfy, by manipulating the availability of preferred males. We capitalize on the recent discovery that female zebra finches (Taeniopygia guttata) prefer males of familiar song dialect. We measured female fitness in captive breeding colonies in which one-third of females were given ample opportunity to choose a mate of their preferred dialect (two-thirds of all males; "relaxed competition"), while two-thirds of the females had to compete over a limited pool of mates they preferred (one-third of all males; "high competition"). As expected, social pairings were strongly assortative with regard to song dialect. In the high-competition group, 26% of the females remained unpaired, yet they still obtained relatively high fitness by using brood parasitism as an alternative reproductive tactic. Another 31% of high-competition females paired disassortatively for song dialect. These females showed increased levels of extra-pair paternity, mostly with same-dialect males as sires, suggesting that preferences were not abolished after social pairing. However, females that paired disassortatively for song dialect did not have lower reproductive success. Overall, females in the high-competition group reached equal fitness to those that experienced relaxed competition. Our study suggests that alternative reproductive tactics such as egg dumping can help overcome the frequency-dependent costs of being selective in a monogamous mating system, thereby facilitating the evolution of female choosiness.

Using Song Dialects to Assess the Migration Strategy of the Golden-crowned Sparrow

Most techniques used to study migration of wild birds require capture for banding or for attachment and/or recovery of tags or transmitters. We took advantage of the fact that the Golden-crowned Sparrow (Zonotrichia atricapilla) sings in winter, combined with published data on the distribution of its distinct song dialects in the breeding range, to assess its migration strategy and migratory connectivity by means of these dialects. Using recordings of the Golden-crowned Sparrow’s song across much of its winter range, we categorized these birds by song type to identify their likely origin in some subset of the breeding range. This method allows examination of migration without the need to capture birds. Our results fit best with a pattern of chain migration, with the northernmost breeders wintering in the northernmost part of the winter range, and the southerly breeders wintering farther south. The results suggest strong migratory connectivity between segments of the breeding and winter ranges, though our small sample size makes it difficult to draw firm conclusions on connectivity.

Female preference for artificial song dialects in the zebra finch (Taeniopygia guttata)

AbstractBirdsong is culturally transmitted, and geographical variations of song have been found in several songbird species. There is evidence that such dialects contribute to reproductive isolation through variation in female preference. In the wild, there is no report of consistent dialects in populations of zebra finches. However, under laboratory conditions, we were able to artificially create different colony‐wide song dialects. In this species, song plays a crucial role in mate choice and the importance of both subadult and adult song experience in shaping song preferences has been well documented. Therefore, we expected females to prefer songs corresponding to their colony's dialect. We measured this preference using an operant test: females could either trigger a song corresponding to their Colony Song Type (CST) sang by an unfamiliar individual, or another conspecific song, corresponding to a Non‐Colony Song Type (N‐CST). Most females preferred the CST over the N‐CST, supporting the idea that zebra finch females exhibit a preference for songs similar to their colony's song. It also reveals that song dialects matter to female zebra finches. It has been proposed that song could be used as an affiliative signal in highly social species. Therefore, preferring the colony dialect could be the consequence of a sexual preference, but also of a social preference. We discuss the potential role of song dialects in the context of social learning.

Complex vocal learning and three-dimensional mating environments

Complex vocal learning, the capacity to imitate new sounds, underpins the evolution of animal vocal cultures and song dialects and is a key prerequisite for human speech and song. Due to its relevance for the understanding of cultural evolution and the biology and evolution of language and music, the trait has gained much scholarly attention. However, while we have seen tremendous progress with respect to our understanding of its morphological, neurological and genetic aspects, its peculiar phylogenetic distribution has remained elusive. Intriguingly, animals as distinct as hummingbirds and humpback whales share well-developed vocal learning capacity in common with humans, while this ability is quite limited in nonhuman primates. Yet, solving this ‘vocal learning conundrum’ may shed light on the constraints ancestral humans overcame to unleash their vocal capacities. To this end I consider major constraints and functions that have been proposed. I highlight an especially promising ecological constraint, namely the spatial dimensionality of the environment. Based on an informal comparative review, I suggest that complex vocal learning is associated with three-dimensional habitats such as air and water. I argue that this is consistent with recent theoretical advances—i.e., the coercion-avoidance and dimensionality hypotheses—and with the long-standing hypothesis that mate choice is a major driver of the evolution and origin of complex vocal learning. However, I stress that multiple functions may apply and that quantitative phylogenetic comparative methods should be employed to finally resolve the issue.

Archaic Dialect of Chaffinch, Fringilla coelebs (Passeriformes, Fringillidae), Song in the Lower-Dnipro Area (South Ukraine) and Its Territorial Relations

Archaic song dialect of Chaffinch (Fringilla coelebs Linnaeus, 1758) is located in the Lower-Dnipro Area. To describe it, we recorded 11673 songs of 2008 males from 43 localities in Southern Ukraine during 2004–2015. This dialect has compound spatial structure and connects with other dialects forming a well developed contact area with them. Its core was located in old forests of the lower stream of the Dnipro River. It has spread from them to the new forests in their outskirts. The complex is separated at dialect level in the cluster analysis. It includes considerable number of original song types. Their elements and structure demonstrate archaic features similar to those of other southern complexes but more modern than the old Carpathian and Danube dialects. It occupies the intermediate position between them and modern dialects of the Forest and Wood-and-Steppe Ukraine by the structure of song and is similar to the dialect of Crimean Chaffinch and the song complex of South-Eastern Ukraine.

Continent-wide Shifts in Song Dialects of White-Throated Sparrows

Hypotheses on regional song variation ("dialects") assume that dialects remain stable within regions, are distinct between regions, and persist within populations over extensive periods [1-3]. Theories to explain dialects focus on mechanisms that promote persistence of regional song variants despite gene flow between regions [4-6], such as juveniles settling in non-natal populations retaining only those songs from their repertoires that match neighbors [7, 8]. It would be considered atypical for a novel song variant to invade and replace the established regional variant. Yet some studies have reported song variants shifting rapidly over time within populations [9-11]. White-throated sparrows, Zonotrichia albicolis, for example, traditionally sing a whistled song terminating in a repeated triplet of notes [12], which was the ubiquitous variant in surveys across Canada in the 1960s [13]. However, doublet-ending songs emerged and replaced triplet-ending songs west of the Rocky Mountains sometime between 1960 and 2000 [11] and appeared just east of the Rockies in the 2000s [14]. From recordings collected over two decades across North America, we show that doublet-ending song has now spread at a continental scale. Using geolocator tracking, we confirm that birds from western Canada, where doublet-ending songs originated, overwinter with birds from central Canada, where the song initially spread. This suggests a potential mechanism for spread through song tutoring on wintering grounds. Where the new song variant has spread, it rose from a rare variant to the sole, regional song type, as predicted by the indirect biased transmission hypothesis [10]. VIDEO ABSTRACT.

Genomic divergence in allopatric Northern Cardinals of the North American warm deserts is linked to behavioral differentiation.

Biogeographic barriers are considered important in initiating speciation through geographic isolation, but they rarely indiscriminately and completely reduce gene flow across entire communities. Explicitly demonstrating which factors are associated with gene‐flow levels across barriers would help elucidate how speciation is initiated and isolation maintained. Here, we investigated the association of behavioral isolation on population differentiation in Northern Cardinals (Cardinalis cardinalis) distributed across the Cochise Filter Barrier, a region of transitional habitat which separates the Sonoran and Chihuahuan deserts of North America. Using genomewide markers, we modeled demographic history by fitting the data to isolation and isolation‐with‐migration models. The best‐fit model indicated that desert populations diverged in the Pleistocene with low, historic, and asymmetric gene flow across the barrier. We then tested behavioral isolation using reciprocal call‐broadcast experiments to compare song recognition between deserts, controlling for song dialect changes within deserts. We found that male Northern Cardinals in both deserts were most aggressive to local songs and failed to recognize across‐barrier songs. A correlation of genomic differentiation and strong song discrimination is consistent with a model where speciation is initiated across a barrier and maintained by behavioral isolation.

Detailed large‐scale mapping of geographical variation of Yellowhammer Emberiza citrinella song dialects in a citizen science project

Song dialects, as a special case of geographical variation in vocalization, are useful tools in the study of a number of topics ranging from cultural evolution to the emergence of reproductive barriers, and thus continue to be the focus of many bird‐song studies. The Yellowhammer Emberiza citrinella is a common Palaearctic bird with a long breeding season and song period, whose distinctive song exhibits clearly distinguishable dialects differing in the composition of the final phrase. The species is therefore particularly suitable for large‐scale studies of dialect distribution involving not only experts but also members of the public. Here we demonstrate that citizen science can indeed allow mapping of songbird dialect distribution on a national scale in unprecedented detail. During the project Dialects of Czech Yellowhammers, which collected almost 4000 recordings over 6 years (2011–2016), we obtained information on dialect distribution for almost 90% of the territory of Czechia. We detected most of the common dialect types known elsewhere in Europe, and these were distributed in a fragmented fashion, with several unusual and rare dialects also detected in small areas. However, the highly scattered distribution of birds using some final phrases traditionally assigned to distinct dialects suggests that classification of Yellowhammer dialects warrants a thorough re‐assessment based on quantitative data. Successful involvement of the public in this and other ongoing citizen science projects has contributed to the establishment of the Yellowhammer as a model species for dialect research. The dataset will serve as a foundation for future studies investigating processes responsible for the origin and maintenance of avian dialects, and may be particularly useful for evaluating their spatial and temporal stability.

Citizen science and wildlife biology: Synergies and challenges

AbstractCitizen science (CS) has evolved over the past decades as a working method involving interested citizens in scientific research, for example by reporting observations, taking measurements or analysing data. In the past, research on animal behaviour has been benefitting from contributions of citizen scientists mainly in the field of ornithology but the full potential ofCSin ecological and behavioural sciences is surely still untapped. Here, we present case studies that successfully appliedCSto research projects in wildlife biology and discuss potentials and challenges experienced. Our case studies cover a broad range of opportunities: large‐scaleCSprojects with interactive online tools on bird song dialects, engagement of stakeholders as citizen scientists to reduce human–wildlife conflicts, involvement of students of primary and secondary schools inCSprojects as well as collaboration with the media leading to successful recruitment of citizen scientists. Each case study provides a short overview of the scientific questions and how they were approached to showcase the potentials and challenges ofCSin wildlife biology. Based on the experience of the case studies, we highlight howCSmay support research in wildlife biology and emphasise the value of fostering communication inCSto improve recruitment of participants and to facilitate learning and mutual trust among different groups of interest (e.g., researchers, stakeholders, students). We further show how specific training for the participants may be needed to obtain reliable data. We considerCSas a suitable tool to enhance research in wildlife biology through the application of open science procedures (i.e., open access to articles and the data on publicly available repositories) to support transparency and sharing experiences.

High levels of gene flow among song dialect populations of the Puget Sound white‐crowned sparrow

AbstractPopulations within a species can show geographic variation in behavioral traits that affect mating decisions or limit dispersal. This may lead to restricted gene flow, resulting in a correlation between behavioral variation and genetic differentiation. Populations of a songbird that differ in a learned behavioral trait, their song dialects, may also differ genetically. If song dialects function as mating barriers, evolutionary processes such as genetic drift should lead to divergence in allele frequencies among dialect populations. The Puget Sound white‐crowned sparrow (Zonotrichia leucophrys pugetensis) is an excellent study system with a well‐defined series of song dialects along the Pacific Northwest coast. A previous study found low genetic differentiation based on four microsatellite loci; however, available loci and analyses techniques have since dramatically improved and allow us to reassess gene flow in this species. We also add extra samples to fill in gaps and add a new level of analysis of geographic variation. Based on acoustic similarities, we group six song dialects into two geographically larger “northern” and “southern” song themes. One southern dialect is acoustically more similar to dialects in the north, which makes the genetic profile of birds singing this dialect particularly interesting. Traditional F‐statistics, analysis of molecular variance as well as Bayesian techniques confirmed the earlier result that geographic variation in song does not correlate with the neutral genetic structure of the sampled dialect populations. The song themes also did not differ genetically, and the origin of the extralimital northern‐theme dialect cannot be determined. We compare this result to findings in several other species and discuss how the timing of learning and dispersal allow vocalizations to vary independently of patterns of genetic divergence.