Vocal Variation Research Articles

Interspecific territoriality despite vocal divergence in two sympatric Laterallus crakes

Territoriality is a widespread behavioral phenomenon that functions for partitioning space and defending resources. Birds tend to defend territories against homospecific individuals through long-distance acoustic signals, but some species also exhibit interspecific territoriality. Two main hypotheses could explain interspecific territoriality mediated by long-distance acoustic signals: (1) misidentification of heterospecifics as homospecifics (misdirected aggression), or (2) recognition of heterospecifics as threats (purposeful aggression). The sympatric Red-and-white crake (Laterallus leucopyrrhus) and the Rufous-sided crake (L. melanophaius) are reciprocally territorial, but the mechanism underlying this interspecific territoriality is not known. We assessed the similarity of territorial long-distance acoustic signals (duet trills) between these crakes in comparison to more closely related species: Red-and-white vs. Rufous-faced crake (L. xenopterus) and Rufous-sided vs. White-throated crake (L. albigularis). Duet trills are two-parted, beginning with soft initial notes audible at close range and followed by a loud-trilled portion audible at long range. We ran univariate comparisons (Kruskal–Wallis), assessed overlap in multivariate acoustic space (PCA), and calculated vocal similarities (cluster analysis; Euclidean distances). The loud-trilled portions of the interspecifically territorial Red-and-white and Rufous-sided crakes occupied completely non-overlapping acoustic spaces, and were not grouped together by vocal similarity. Their territorial signals were more similar to those of their closest relatives, than between them. Soft initial notes of duet trills were in general very different between species, and their general structure matched the phylogenetic relationships. We found no evidence for strong character convergence and partial phylogenetic conservatism in signal explained overall similarities in vocalizations among species. The highly divergent vocalizations of Red-and-white and Rufous-sided crakes in conjunction with their interspecific territorial responses suggest that recognition of heterospecifics as threats, and not misidentification of heterospecifics as homospecifics, mediates their vocal responses. Our study adds evidence showing that interspecific territoriality represents purposeful heterospecific aggression and is not the product of misdirected homospecific aggression.

Geographic variability in the alarm calls of the European ground squirrel.

Geographic variability in vocalizations has been documented in many mammalian species. We examined to what extent it applies to the alarm calls of the European ground squirrel Spermophilus citellus. We recorded the calls of 82 adult individuals from 5 natural colonies in the Czech Republic and 24 adult individuals from an artificial seminatural colony located in a Czech zoo. The founders of this colony originated from 4 different natural colonies in the Czech Republic. Our results showed that there are hardly any differences in the acoustic structure of the alarm calls between male and female European ground squirrels. Discriminant function analysis showed the highest degree of discriminability for the most isolated sites (54–74% of individuals classified correctly), whereas the lowest degree of discriminability was found for 2 interconnected colonies (38–40% individuals classified correctly). Individuals from the artificial seminatural colony were often classified correctly to this colony (58% classified correctly); however, the precision of the classification was comparatively relatively low, that is, many individuals from other colonies were incorrectly classified into this seminatural colony. This likely corresponds to the different origins of its founders. These findings indicate that there is a rather substantial geographic variability in the alarm calls of the European ground squirrel, and our study highlights its possible impact on conservation measures such as establishing artificial colonies or reintroductions.

Vocal divergence is concordant with genomic evidence for strong reproductive isolation in grasshopper mice (Onychomys).

Behavioral barriers to gene flow often evolve faster than intrinsic incompatibilities and can eliminate the opportunity for hybridization between interfertile species. While acoustic signal divergence is a common driver of premating isolation in birds and insects, its contribution to speciation in mammals is less studied. Here we characterize the incidence of, and potential barriers to, hybridization among three closely related species of grasshopper mice (genus Onychomys). All three species use long‐distance acoustic signals to attract and localize mates; Onychomys arenicola and Onychomys torridus are acoustically similar and morphologically cryptic whereas Onychomys leucogaster is larger and acoustically distinct. We used genotyping‐by‐sequencing (GBS) to test for evidence of introgression in 227 mice from allopatric and sympatric localities in the western United States and northern Mexico. We conducted laboratory mating trials for all species pairs to assess reproductive compatibility, and recorded vocalizations from O. arenicola and O. torridus in sympatry and allopatry to test for evidence of acoustic character displacement. Hybridization was rare in nature and, contrary to prior evidence for O. torridus/O. arenicola hybrids, only involved O. leucogaster and O. arenicola. In contrast, laboratory crosses between O. torridus and O. arenicola produced litters whereas O. leucogaster and O. arenicola crosses did not. Call fundamental frequency in O. torridus and O. arenicola was indistinguishable in allopatry but significantly differentiated in sympatry, a pattern consistent with reproductive character displacement. These results suggest that assortative mating based on a long‐distance signal is an important isolating mechanism between O. torridus and O. arenicola and highlight the importance of behavioral barriers in determining the permeability of species boundaries.

Validity of Vocal Communication and Vocal Complexity in Young Children with Autism Spectrum Disorder.

To identify valid measures of vocal development in young children with autism spectrum disorder in the early stages of language learning, we evaluated the convergent validity, divergent validity, and sensitivity to change (across 12months) of two measures of vocal communication and two measures of vocal complexity through conventional coding of communication samples. Participants included 87 children with autism spectrum disorder (M = 23.42months at entry). All four vocal variables demonstrated consistent evidence of convergent validity, divergent validity, and sensitivity to change with large effect sizes for convergent validity and sensitivity to change. The results highlight the value of measuring vocal communication and vocal complexity in future studies.

Analysis of duet vocalizations in Myiothlypis leucoblephara (Aves, Parulidae)

Bird vocalizations might be used for specific recognition, territorial defense, and reproduction. Bioacoustic studies aim to understand the production, propagation and reception of acoustic signals, and they are an important component of research on animal behavior and evolution. In this study we analyzed the sound structure of duet vocalizations in pairs of Myiothlypis leucoblephara and evaluated whether the vocal variables differ among pairs and if there are differences in temporal characteristics and frequency of duets between pairs in forest edges vs. forest interior. Vocalizations were recorded from 17 bird pairs in three remnants of Atlantic Forest in southern Brazil. Six of the bird pairs were situated at the edge of the forest remnant, and 11 were in the interior of the remnant. The duets of different pairs between forest areas showed descriptive differences in the frequency, number of notes per call, and time between issuance of calls, with the main distinguishing feature being a change in frequency of a few notes in the second part of the musical phrase. The minimum frequency of vocalization was reduced at the private area than in the other two remnants (p <0.05). The duets of birds in the forest edge and forest interior did not significantly differ in minimum or maximum frequency of phrases (p> 0.05), phrase duration (p> 0.05) or number of notes per phrase (p> 0.05). Myiothlypis leucoblephara did not show a specific pattern with respect to issue of phrases in duets, but instead showed five different patterns, which were variable among pairs. There was a sharp decline or alternation in frequency between notes in the second part of the musical phrase for recognition among pairs. Variation in vocalization among M. leucoblephara duets may play a role in pair recognition.

Management of Vocal Fold Paralysis and Dysphagia for Neurologic Malignancies in Children.

To evaluate our experience with a significant number of brain malignancy-related vocal fold paralysis patients and their response to vocal cord-related therapies. Vocal fold paralysis is a potentially devastating complication of various types of pediatric diseases and surgeries that can lead to significant vocal and swallowing difficulties. While there is significant data in the literature on outcomes of children treated for vocal fold paralysis following cardiac or thyroid surgery, there is a scarcity of such information on children following the treatment of neurologic malignancy. Records of 19 patients at a tertiary center who were treated for neurologic malignancies and developed either unilateral or bilateral vocal fold paralysis were reviewed for vocal fold pathology and vocal fold paralysis treatment-related variables, including initial diagnosis, management with observation or speech therapy, duration of therapy, pre- and postintervention swallow studies, and surgical intervention. Bilateral vocal fold paralysis was noted in 26% (5/19) patients. Eighty-four percent (16/19) of patients had stable or improved ability to vocalize and swallow following therapy. There was no statistically significant difference in speech or swallowing improvement after speech therapy alone or speech therapy in combination with injection laryngoplasty (P = .25). No complications were noted with surgical intervention. Patients with vocal fold paralysis secondary to neurologic malignancy can have an improvement in speech and swallowing after a variety of treatments, including speech therapy or early injection laryngoplasty. There was no statistically significant difference in improvement based on the type of intervention utilized. A larger sample size is needed to conclude whether surgical intervention combined with speech therapy leads to more rapid and significant functional improvement than speech therapy alone.

Is neurogenesis in two songbird species related to their song sequence variability?

Neurogenesis takes part in the adult songbird brain and new neurons are integrated into the forebrain including defined areas involved in the control of song learning and production. It has been suggested that the new neurons in the song system might enable vocal variability. Here, we examined the basal levels of neurogenesis in two songbird species, zebra finch ( Taeniopygia guttata) and Bengalese finch ( Lonchura striata var. domestica), which do not learn new song elements as adults but differ in the level of song sequence variability. We found that Bengalese finches had less linear and stereotyped song sequence and a higher number of newborn cells in the neurogenic subventricular zone (SVZ) as well as the number of newly born neurons incorporated into the vocal nucleus HVC (used as a proper name) in comparison to zebra finches. Importantly, this vocal sequence variability in Bengalese finches correlated with the number of new neurons in the vocal nucleus HVC and more plastic song was associated with higher neuronal incorporation. In summary, our data support the hypothesis that newly generated neurons facilitate behavioural variability.

Sex-specific effects of testosterone on vocal output in a tropical suboscine bird

Vocal signals are important in territoriality and mate attraction across animal taxa. Vocalizations are particularly elaborate in some groups, such as songbirds, which learn their songs, but much remains to be known about the physiological mechanisms that produce variation, especially in vocalizations of nonlearners. We address the extent that androgen treatment of female and juvenile golden-collared manakins, Manacus vitellinus, activate the male-like ‘chee-poo’ vocalization to determine (1) the extent that the vocal circuitry is developed and sensitive to androgens in females and (2) to identify the characteristics, including finer acoustic features, of vocal behaviour that are influenced by androgens in females and young males. We analysed recordings of nonbreeding females and juvenile males given implants containing testosterone (T) or blank implants during a period of 3 weeks in an outdoor aviary in Panama. T-treated females, but not control females, produced chee-poos, and their vocalizations showed consistent differences in acoustic features from those of males. This indicates that the neuromuscular systems are well developed or relatively rapidly developed in response to T administration in females. Both T-treated and control juvenile males produced chee-poos, although vocal production was higher in the treatment group. Surprisingly, T treatment of juvenile males resulted in chee-poos with increased acoustic similarity to those of females, such as increased duration and frequency bandwidth. These features may indicate an important role for chee-poos in aggressive interactions. Future work will address the contributions of central and peripheral components in vocal variation in golden-collared manakins.

Современные тенденции в сценических жанрах как предмет освоения в курсе истории эстрадной и джазовой музыки (на примере рок-оперы «Легенда Ксентарона»)

The work explores the interaction of the structure and content of the modern musical and scenic genre, rock opera. On the basis of the rock opera “The Legend of Xentaron” staged by “Epidemic”, a Russian power metal group, authors show characteristics of the rock opera of the 21st century, performing and instrumental structure, other components of the new musical and scenic action influencing the listener, the trend of influence of a genre of a fantasy on characteristic stylistic features of a genre of a rock opera is considered. The authors pay special attention to the analysis of dramaturgy in the rock opera “The Legend of Xentaron”, on the basis of which it is characterized as a mixed form, synthesizing the techniques of conflict and epic dramaturgy. At the same time, they revealed both typical and already traditional features for this musical stage genre, as well as modern trends in its evolution. This refers to such new features as: serial, formulas, stereotyping, replicability. The inclusion of the results in the study of “History of variety and jazz music” will help university students to get an idea about new trends in development of the phenomena of performing art, styles, genres, directions and the repertoire in the field of vocal and instrumental variety and jazz music.

Reevaluation of the taxonomic positions of members of the Epinecrophylla fjeldsaai (Aves: Passeriformes: Thamnophilidae) antwren complex including E. fjeldsaai based on vocalizations

The northwestern populations in the dead-leaf-foraging Epinecrophylla haematonota complex of thamnophilid antwrens includes E. pyrrhonota, E. fjeldsaai, and E. haematonota. Their taxonomic position has been the subject of recent debate. Divergence in homologous vocalizations provides a principal measure of reproductive isolation and species status for thamnophilid antbirds under the biological species concept, but until recently their evaluation as species has been hampered by the paucity of recordings of E. fjeldsaai. That insufficiency has been remedied, enabling an analytic comparison of vocalizations of the 3 taxa. The results of this analysis led to the recommendation that the 3 taxa be ranked as subspecies of Epinecrophylla haematonota.

Song of my people: dialect differences among sympatric social groups of short-finned pilot whales in Hawai’i

In many social species, acoustic dialects are used to differentiate among social groups within a local population. These acoustic dialects and their corresponding social groups are often related to distinct foraging behaviors or spatial movement patterns, and it is possible that vocal repertoire variability is one of the proximate mechanisms driving or maintaining genetic and ecological diversity at a subspecies level in social species. Short-finned pilot whales (Globicephala macrorynchus) inhabiting Hawaiian waters have a stable hierarchical social structure, with familial social units associating in larger social clusters within island-associated communities. In this study, we test the hypothesis that sympatric social groups of short-finned pilot whales have acoustically differentiated dialects, which may be used to maintain the social structure. We first examined call composition of social calls collected from photographically identified social clusters of short-finned pilot whales around the Main Hawaiian Islands, using a catalog of manually classified calls, and found that call composition differed among clusters. We then conducted ANOVA and support vector machine (SVM) learning analyses of the acoustic features of social calls. Social clusters were significantly differentiated in their acoustic features, and the SVM classification accuracy was 60%. These results indicate that vocal repertoire reflects social segregation in short-finned pilot whales and may be a driving mechanism of differentiation, potentially contributing to genetic diversity within populations. This suggests divergent acoustic population structure; however, the small sample size in this study decreases the ability to detect acoustic differences among groups. Additional sampling will improve our power to detect acoustic differences among social clusters of Hawaiian pilot whales and improve classification accuracy. The pattern described here highlights the importance of increasing the spatial and temporal resolution of conservation and management plans for this species, in order to conserve subpopulation genetic and social structure. In some species, vocal repertoires differ among social groups or populations of a species that use the same habitat. These differences, called dialects, are thought to be important to maintaining segregation among groups of animals with overlapping distributions, and in some cases may increase intra-specific ecological or genetic variability. This study is the first to provide evidence that sympatric social clusters of short-finned pilot whales have different vocal repertoires, and that vocal repertoire within groups may change with behavioral context. In terrestrial (e.g., elephants) and marine (e.g., killer whales, sperm whales) species with similarly stable social hierarchies, where acoustic dialects, genetic diversity, and/or ecological variability are linked with social structure, anthropogenic stressors have precipitated rapid declines in abundance with slow or nonexistent recovery. Given the myriad threats faced by short-finned pilot whales in the Hawaiian Islands, including fisheries bycatch, military and commercial anthropogenic noise, and vessel strikes, understanding intra-population social structure and its links with genetic structure and ecological variability is imperative to the proper conservation and management of this species.

Reduced song complexity in founder populations of a widely distributed songbird

Reduced vocal diversity in founder populations of songbirds is particularly well described in congeners and conspecifics introduced to remote islands but has rarely been examined in species that have been introduced to both island and mainland systems across an expansive geographical range. We examined male between‐ and within‐song complexity variations between founder and native populations of the widely distributed Common Myna Acridotheres tristis and predicted reduced complexity within individuals from founder populations. The percentage of unique songs within a repertoire and within‐song complexity were significantly lower in Mynas from founder populations. This reduced song complexity suggests that vocal founder effects may be exhibited in both island and mainland founder populations.

Vocal divergence between two disjunct populations of Giant Antshrike (Batara cinerea) is related to environmental conditions

AbstractVariation in the avian vocal signals emitted may have a significant impact on species evolution. Vocal divergence in suboscine species like Giant Antshrike (Batara cinerea) may be associated with selective adaptation, since learning has little influence on vocal development and variation in acoustic structure cannot be attributed to learning deviation. Consequently, tracheophone suboscine species are ideal subjects to explore vocal variation, since cultural evolution does not seem to influence vocal variation in this group. Environmental conditions may determine the selection of vocal features because acoustic transmission could be attenuated under certain conditions of temperature, humidity and vegetation cover. Here, we examined vocalizations of Giant Antshrike and assessed possible acoustic variations between two disjunct groups (Andean and Atlantic), correlating the differences to the environmental structure. Univariate and multivariate analysis show temporal and spectral differences between both groups. Andean individuals produce vocalizations with longer duration, faster trill rates, shorter syllable duration and higher frequencies. Environmental features are different between the two populations, and they are correlated to the acoustic structure of vocalizations. Temporal variations arise directly from climatic influence, while spectral divergence could be a secondary effect of morphological adaptation to habitat structure.

Aging of speech production, from articulatory accuracy to motor timing.

Despite the huge importance of spoken language production in everyday life, little is known about the manner and extent to which the motor aspects of speech production evolve with advancing age, as well as the nature of the underlying senescence mechanisms. In this cross-sectional group study, we examined the relationship between age and speech production performance using a nonlexical speech production task in which spoken syllable frequency and phonological complexity were systematically varied to test hypotheses about underlying mechanisms. A nonprobabilistic sample of 60 cognitively healthy adults (18-83 years) produced meaningless nonwords aloud as quickly and accurately as possible. Error rate, vocal reaction time (RT), vocal RT variability, vocal response duration, and vocal response duration variability were used as dependent variables to characterize speech production performance. The results showed an overall increase in error rate, which occurred mainly in the final syllable position (coda). There was also an increase in vocal response duration and in duration variability with age, which was moderated by phonological complexity and syllable frequency. Finally, we also found an age-related change in the relationship between vocal RT and vocal response duration. Together, these findings were interpreted as reflecting an age-related decline in the planning and execution of speech movements in cognitively healthy adults. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

EFL Teachers’ Verbal and Nonverbal Immediacy: A Study of its Impact on Students’ Emotional States, Cognitive Learning, and Burnout

Effective teacher–student interaction is an essential element of an ideal classroom which promotes the opportunity for expanded learning and stimulates the connections between students and teacher. The focus of the present study is on an instructional communication element that is teacher immediacy. It is defined as the mutual sensory and psychological stimulation between teacher and students. It can be verbal or nonverbal. Verbal immediacy is characterized as stylistic differences in expression from which like–dislike is inferred and includes using humor or personal examples, getting feedback, or even calling students by name. Nonverbal immediacy encompasses behaviors such as appropriate eye contact, the use of gestures, movement about the classroom, smiling, and vocal variety. In particular, the present study sought to explore the impact of English as a foreign language (EFL) teachers’ perceived verbal/nonverbal immediacy on students’ self-actualization, stress-control, and self-esteem. Moreover, it examined the role of EFL teachers’ immediacy behaviors in students’ cognitive learning and emotional exhaustion, which is a burnout subscale. To this end, 206 EFL students participated from selected universities of Mashhad, a city in northeast of Iran. The respondents were asked to complete five inventories about themselves and the previous EFL teacher they had had classes with. The results of structural equation modeling demonstrated that teacher immediacy behavior had a positive significant impact on all student-related variables: stress tolerance (β = .65, t = 7.59), self-actualization (β = .69, t = 8.02), self-esteem (β = .63, t = 7.71), burnout (β = .31, t = 4.05), and cognitive learning (β = .45, t = 6.08). The highest impact was exerted on self-actualization and self-esteem.

Components of variation in female common cuckoo calls

Investigations on bird vocalizations have largely focused on males. Female vocalizations are widespread in birds but few studies have investigated female vocal characteristics, particularly in non-Passeriformes. In this study, we use new field recordings from China, and calls available from an online sound library to examine temporal patterns, call consistency and geographical variation in vocalizations of female common cuckoos Cuculus canorous. The peak in vocal activity (both male and female) was in the morning, which contrasts to what would be predicted if the sole function of the female call was to distract the attention of hosts after parasitizing a host’s nest in the afternoon. Both male and female common cuckoos were more vocally active in sunny weather, than rainy weather. We also found larger intra-individual variation in female rather than in male calls, which may benefit female cuckoos by increasing stimulation to host species. Peak frequency of female calls decreased with increased latitude, while differences in female call features were not associated with geographic distance. In summary, our findings that female calls are used in the morning, rather than at peak egg laying, yet are highly variable and show little geographic patterns suggest that the function of these female calls may be more variable and intricate than previously thought. However, because research on female vocalizations is underrepresented, future studies are still needed.

The Avian Basal Ganglia Are a Source of Rapid Behavioral Variation That Enables Vocal Motor Exploration.

The basal ganglia (BG) participate in aspects of reinforcement learning that require evaluation and selection of motor programs associated with improved performance. However, whether the BG additionally contribute to behavioral variation ("motor exploration") that forms the substrate for such learning remains unclear. In songbirds, a tractable system for studying BG-dependent skill learning, a role for the BG in generating exploratory variability, has been challenged by the finding that lesions of Area X, the song-specific component of the BG, have no lasting effects on several forms of vocal variability that have been studied. Here we demonstrate that lesions of Area X in adult male zebra finches (Taeniopygia gutatta) permanently eliminate rapid within-syllable variation in fundamental frequency (FF), which can act as motor exploration to enable reinforcement-driven song learning. In addition, we found that this within-syllable variation is elevated in juveniles and in adults singing alone, conditions that have been linked to enhanced song plasticity and elevated neural variability in Area X. Consistent with a model that variability is relayed from Area X, via its cortical target, the lateral magnocellular nucleus of the anterior nidopallium (LMAN), to influence song motor circuitry, we found that lesions of LMAN also eliminate within-syllable variability. Moreover, we found that electrical perturbation of LMAN can drive fluctuations in FF that mimic naturally occurring within-syllable variability. Together, these results demonstrate that the BG are a central source of rapid behavioral variation that can serve as motor exploration for vocal learning.SIGNIFICANCE STATEMENT Many complex motor skills, such as speech, are not innately programmed but are learned gradually through trial and error. Learning involves generating exploratory variability in action ("motor exploration") and evaluating subsequent performance to acquire motor programs that lead to improved performance. Although it is well established that the basal ganglia (BG) process signals relating to action evaluation and selection, whether and how the BG promote exploratory motor variability remain unclear. We investigated this question in songbirds, which learn to produce complex vocalizations through trial and error. In contrast with previous studies that did not find effects of BG lesions on vocal motor variability, we demonstrate that the BG are an essential source of rapid behavioral variation linked to vocal learning.

Self-perception of quality of life in patients with functional voice disorders: the effects of psychological and vocal acoustic variables.

Functional voice disorders (FVD) are multifactorial and may have a significant impact on the patients' quality of life (QOL). The aim of this study was to explore and analyze the relationship between the VHI scores, psychological variables, and objective voice measurements, and to develop a psychological and/or vocal acoustic model for the overall self-perceived evaluation of quality of life for three different types of FVD. After ENT examination, 83 women were classified into three groups: psychogenic voice disorder (PVD = 39), primary muscle tension voice disorder (MTVD1 = 16), and secondary muscle tension voice disorder (MTVD2 = 28). All patients were evaluated according to a multidisciplinary assessment protocol, which included the self-evaluation of quality of life (Voice Handicap Index, VHI), psychological evaluation (Hamilton Rating Scales for Depression(HAM-D) and for Anxiety(HARS), and Temperament Evaluation of Memphis, Pisa, Paris and San Diego-Auto questionnaire(TEMPS-A)), and vocal acoustic analysis [mean fundamental frequency (F0, Hz), jitter (local, %), shimmer (local, %), andharmonic-to-noise ratio (HNR, dB)]. Our findings revealed a moderate impact on QOL, regardless of the type of FVD. There were significant correlations between VHI scores, psychological variables, and voice perturbation parameters, with the exception of the MTVD1 and MTVD2 groups. The stepwise multiple linear regression analysis suggested that QOL could be explained by: anxious temperament together with shimmer in PVD group, jitter in the MTVD1 group, and depressive temperament in the MTVD2 group. Affective temperaments and/or voice perturbation parameters were meaningful predictors of self-evaluation of quality of life in patients with different types of FVD.

Understanding sources of variance and correlation among features of Bornean gibbon (Hylobates muelleri) female calls

Acoustic signals serve important functions in mate choice, resource defense, and species recognition. Quantifying patterns and sources of variation in acoustic signals can advance understanding of the evolutionary processes that shape behavioral diversity more broadly. Animal vocalization datasets are inherently multivariate and hierarchical, wherein multiple features are estimated from calls of many individuals across different recording locations. Patterns of variation within different hierarchical levels-notwithstanding the challenges they present for modeling and inference-can provide insight into processes shaping vocal variation. The current work presents a multivariate, variance components model to investigate three levels of variance (within-female, between-female, and between-site) in Bornean gibbon calls. For six of the eight features estimated from call spectrograms, between-female variance was the most important contributor to total variance. For one feature, trill rate, there were site-level differences, which may be related to geographic isolation of certain gibbon populations. There was also a negative relationship between trill rate and duration of the introduction, suggesting trade-offs in the production of gibbon calls. Given substantial inter-individual variation in gibbon calls, it seems likely that there has been selection to confer information regarding caller identity, but mechanisms leading to site-level variation in trill rate remain to be determined.

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.