Book

Nature's music: The science of birdsong

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Abstract

The voices of birds have always been a source of fascination. Nature's Music brings together some of the world's experts on birdsong, to review the advances that have taken place in our understanding of how and why birds sing, what their songs and calls mean, and how they have evolved. All contributors have strived to speak, not only to fellow experts, but also to the general reader. The result is a book of readable science, richly illustrated with recordings and pictures of the sounds of birds. Bird song is much more than just one behaviour of a single, particular group of organisms. It is a model for the study of a wide variety of animal behaviour systems, ecological, evolutionary and neurobiological. Bird song sits at the intersection of breeding, social and cognitive behaviour and ecology. As such interest in this book will extend far beyond the purely ornithological - to behavioural ecologists psychologists and neurobiologists of all kinds.
... The first mechanism is used by open-ended learners of songbirds with extremely large song repertoires [4]; the second mechanism involves encoding information by simple changes in frequency and amplitude within syllables or notes [7,8], which is a ubiquitous strategy used by vertebrates and many groups of invertebrates; and the third mechanism of encoding information is by changing the temporal distribution of vocalizations, such as temporal characteristics and delivery rate [9][10][11], to express behavioral motivations [6,12]. Therefore, not only acoustic communication consisting of diverse types of syllables and elements expressing various meanings [13][14][15][16], the simple vocalizations, such as referential alarm calls can indicate categories of predators, or even predators' behaviors [17][18][19]. For instance, noisy miner (Manorina melanocephala) emits 'aerial' alarm calls (high-frequency) to airborne raptor and produces 'chur' alarm calls (low-frequency and broad bandwidth) to terrestrial or perched raptor [20]. ...
... Additionally, we evaluated different hypotheses for the relationship between the structure and presumed function of vocalizations among acoustic environments. By studying how a "simple repertoire" functions during breeding, we aimed to broaden our understanding of how diverse behavioral motivations are encoded in relatively simple systems [13]. ...
... common coots emitted call d when they were foraging for food on the water surface or in the nest; d had a significantly higher frequency compared with the other 3 calls. Because the location of vocalization producers can be easily detected by signal receivers through high-frequency calls [13,19], d may be used to determine the location of mates and be used as a general contact call. Call b is the only call that we recorded for parentoffspring communication, which had the lowest fundamental frequency (F 0 ) among all call types. ...
Article
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Background Although acoustic communication plays an essential role in the social interactions of Rallidae, our knowledge of how Rallidae encode diverse types of information using simple vocalizations is limited. We recorded and examined the vocalizations of a common coot (Fulica atra) population during the breeding season to test the hypotheses that 1) different call types can be emitted under different behavioral contexts, and 2) variation in the vocal structure of a single call type may be influenced both by behavioral motivations and individual signature. We measured a total of 61 recordings of 30 adults while noting the behavioral activities in which individuals were engaged. We compared several acoustic parameters of the same call type emitted under different behavioral activities to determine how frequency and temporal parameters changed depending on behavioral motivations and individual differences. Results We found that adult common coots had a small vocal repertoire, including 4 types of call, composed of a single syllable that was used during 9 types of behaviors. The 4 calls significantly differed in both frequency and temporal parameters and can be clearly distinguished by discriminant function analysis. Minimum frequency of fundamental frequency (F0min) and duration of syllable (T) contributed the most to acoustic divergence between calls. Call a was the most commonly used (in 8 of the 9 behaviors detected), and maximum frequency of fundamental frequency (F0max) and interval of syllables (TI) contributed the most to variation in call a. Duration of syllable (T) in a single call a can vary with different behavioral motivations after individual vocal signature being controlled. Conclusions These results demonstrate that several call types of a small repertoire, and a single call with function-related changes in the temporal parameter in common coots could potentially indicate various behavioral motivations and individual signature. This study advances our knowledge of how Rallidae use “simple” vocal systems to express diverse motivations and provides new models for future studies on the role of vocalization in avian communication and behavior.
... Birdsong is one such example, as it is thought to communicate only behavioural states (e.g. territoriality) in which the 'meaning' does not change regardless of the number or type of syllables used (Marler & Slabbekoorn, 2004;Catchpole & Slater, 2008). Particular attributes of song, however, may still convey discrete information -for example, long syllables might be correlated with large body sizes, or high trill rates with high-quality territories (Marler & Slabbekoorn, 2004;Catchpole & Slater, 2008). ...
... territoriality) in which the 'meaning' does not change regardless of the number or type of syllables used (Marler & Slabbekoorn, 2004;Catchpole & Slater, 2008). Particular attributes of song, however, may still convey discrete information -for example, long syllables might be correlated with large body sizes, or high trill rates with high-quality territories (Marler & Slabbekoorn, 2004;Catchpole & Slater, 2008). ...
... Song is used by a wide variety of taxa across the animal kingdom for purposes such as mate attraction and territorial defence (Marler & Slabbekoorn, 2004;Catchpole & Slater, 2008). ...
Thesis
Full-text available
Short-tailed bats; Mystacina tuberculata; singing behaviour in bats; social organisation
... For instance, in red deer (Cervus elaphus), females are preferentially attracted by high roaring rate and low-pitched roars, emitted by large males, which have a better reproductive success than small males . In several songbird species, females are more attracted by males singing with a high song rate, which have a better territory quality, body condition, or feeding rate, and thus a higher reproductive success (reviewed in Marler & Slabbekoorn, 2004 is crucial in these species due to their particular breeding ecology (reviewed in Schreiber & Burger, 2001). Seabirds have distinct feeding and nesting areas: they feed at sea, while they breed on land. ...
... Low frequencies (under 2 kHz) generally propagate further than high frequencies, most absorbed by the atmosphere (Naguib & Wiley, 2001;Marler & Slabbekoorn, 2004). Low frequencies emitted close to the ground are filtered and degraded too (e.g., "ground effect": Morton, 1975;Marten et al., 1977). ...
... For instance, in red deer (Cervus elaphus), females are preferentially attracted by high roaring rate and lowpitched roars, emitted by large males, which have a better reproductive success than small males ). In several songbird species, females are more attracted by males singing with a high song rate, which have a better territory quality, body condition, or feeding rate, and thus a higher reproductive success (reviewed in Marler and Slabbekoorn 2004). ...
Thesis
Comme Bradbury et Verhencamp (1998) l’ont joliment dit, la communication est « la colle maintenant les sociétés animales » car elle est le fondement de nombreux comportements sociaux chez la majorité des espèces. Les pétrels fouisseurs offrent une excellente opportunité d’étudier la communication vocale dans un environnement qui, de prime abord, semble désavantageux. En effet, ces oiseaux marins se regroupent au cours de la saison de reproduction en denses colonies. En dépit des turbulences climatiques (ex. vents violents), des interférences vocales liées à la présence d’autres oiseaux et de la présence de prédateurs qui chassent à l’ouïe, les vocalisations sont à la base des interactions sociales. Durant ma thèse, je me suis intéressée à deux espèces de pétrels fouisseurs phylogénétiquement proches : le pétrel bleu Halobaena caerulea et le prion de la Désolation Pachyptila desolata, tous deux connus pour leurs capacités olfactives développées. En dépit des contraintes environnementales, de la pression de prédation et la possibilité de communiquer via des signaux olfactifs, la communication vocale devrait procurer des bénéfices jusqu’alors méconnus. A l’aide d’expériences de repasse et d’attractivité menées sur un site de reproduction des oiseaux, à Kerguelen, mon objectif a été d’étudier les déterminismes et implications des cris des mâles dans le choix de partenaire des femelles. Les résultats de la présente thèse soulignent : (i) la stratégie de codage de l’information statique (morphologie et identité individuelle) et dynamique (motivation) au niveau des caractéristiques spectrales et temporelles des cris de mâles ; (ii) en quoi la détectabilité du cri et surtout l’information contenue influencent le choix du partenaire par les femelles : et (iii) le rôle joué par le terrier dans la propagation du cri et le choix du partenaire par les femelles. Les deux espèces étudiées ici montrent des similarités dans leurs stratégies vocales et de codage de l’information, ce qui suggère que les mêmes contraintes environnementales sur la communication longue distance ont modifié les signaux de manière similaire. Ces résultats enrichissent nos connaissances sur la manière dont les oiseaux nichant en terriers, très peu étudiés, communiquent dans un environnement contraignant.
... For a receiver, decoding information from the vocalization of an emitter outside its field of view can be critical, to the extent of determining its survival (Hollen & Radford, 2009;Magrath et al., 2010;Marler & Slabbekoorn, 2004;Seddon et al., 2002). This is an especially challenging task in crowded social environments where multiple individuals vocalize simultaneously and levels of background noise are high (Marler & Slabbekoorn, 2004), a common scenario in most social and group-living animals (Aubin, 2004;Charrier et al., 2001;Mathevon, 1997). ...
... For a receiver, decoding information from the vocalization of an emitter outside its field of view can be critical, to the extent of determining its survival (Hollen & Radford, 2009;Magrath et al., 2010;Marler & Slabbekoorn, 2004;Seddon et al., 2002). This is an especially challenging task in crowded social environments where multiple individuals vocalize simultaneously and levels of background noise are high (Marler & Slabbekoorn, 2004), a common scenario in most social and group-living animals (Aubin, 2004;Charrier et al., 2001;Mathevon, 1997). In this context, vocal signals can encode information about the sex, age or size of the emitter, which can indirectly provide information regarding the emitter's rank or experience and allow for effective group coordination or antipredator responses (Fischer et al., 2004;Ghazanfar et al., 2007;Woods et al., 2018). ...
... Brindley, 1991;Godard & Wiley, 1995). However, the most ancient vocalizations that are common and widespread among most, if not all, bird species are innate calls (Kondo & Watanabe, 2009;Marler & Slabbekoorn, 2004). Often, individuals produce multiple calls that differ in function (Adreani et al., 2020;Clay et al., 2012;D'Amelio, Klumb et al., 2017;Marler, 2004;Marler & Slabbekoorn, 2004;Seddon et al., 2002). ...
Article
Full-text available
Vocal communication in group-living animals represents a major challenge when multiple individuals call simultaneously and generate a complex soundscape. Decoding relevant information from a vocal signal and its emitter can determine the survival of the receiver. In hierarchical social groups, information on sex, size and age can provide relevant context for vocal signals. Ultimately, individual vocal recognition is a keystone in vocal communication systems, especially in the context of sociality. Greylag geese (Aves: Anseriformes) are a basal, gregarious and highly social species, and adults produce a distance call when approaching or leaving the flock. In this study we (1) quantified the acoustic properties of distance calls to test whether they can provide information on the sex, size and age of the emitter, (2) evaluated whether distance calls have individual properties, from the sender's perspective, (3) tested whether receivers discriminate distance calls depending on the emitter's identity and (4) explored whether an individual's response strength towards its partner's distance call is associated with fitness-related traits (i.e. pair bond duration and average number of offspring per year). We recorded distance calls of individually marked geese, quantified the variation in call acoustic properties and carried out a playback experiment in the wild. Distance calls encoded information about the sex of the goose, but not its age or size. From the emitter's perspective, we found some support for individuality in distance calls. From the receiver's perspective, geese were capable of recognizing distance calls from different individuals. Finally, the response strength towards playback of the partner's call was positively correlated with pair bond duration. Vocal recognition has been proposed to be tightly related to social structure, the evolution of sociality and vocal learning. Here, we uncovered vocal recognition of individual affiliative calls in a social bird from the most basal avian group studied so far.
... With the ongoing global crisis of biodiversity loss, passive acoustic monitoring has gained popularity in both aquatic and terrestrial environments (Magurran et al., 2010;Blumstein et al., 2011;Parks et al., 2014;Linke et al., 2018;Sugai et al., 2019b), employing sound to monitor wildlife. Animal sounds are diverse and varied, and play a critical role in advertising territories and attracting mates (Marler and Slabbekoorn, 2004;Bradbury and Vehrencamp, 2011), as well as echolocation in some species (Griffin, 1958). Acoustic signal parameters and signaling strategies are influenced by noise from biotic and abiotic sources, structural features of the environment (Morton, 1975;Marten and Marler, 1977;Wiley and Richards, 1978;Wiley, 1991;Aubin and Jouventin, 1998;Nemeth et al., 2002;Blumenrath and Dabelsteen, 2004;Brumm and Slabbekoorn, 2005;Bee and Micheyl, 2008;Brumm and Naguib, 2009;Ruppé et al., 2015;Templeton et al., 2016), and the morphological constraints imposed by emitter geometry (Podos, 2001;Riede et al., 2006;Kounitsky et al., 2015). ...
... In bats, where time-frequency parameters of echolocation pulses have a significant effect on perception and navigation, species occupying the same habitat may possess convergent signals (Parsons and Jones, 2000;Jones and Holderied, 2007). Other vocalizations may also converge owing to conserved function, including alarm calls that are critical for survival (Marler and Slabbekoorn, 2004;Braune et al., 2008). Acoustic adaptation remains debated in the field (Ey and Fischer, 2009), and more studies are necessary to elucidate how ecological processes drive acoustic signal evolution. ...
... Segregation in space or stratification of singing heights have been documented in diverse taxa [insects: Jain and Balakrishnan, 2012), birds: (Nemeth et al., 2002;Chitnis et al., 2020), bats: (Kalko and Handley, 2001;Kennedy et al., 2014)]. This pattern is putatively linked to maximizing sound transmission at a particular location (Miller and Degn, 1981;Dabelsteen et al., 1993;Nemeth et al., 2002;Marler and Slabbekoorn, 2004;Mathevon et al., 2005;Barker and Mennill, 2009;Kirschel et al., 2009a;Sprau et al., 2012;Núñez et al., 2019), or to indirect partitioning as a result of other ecological processes (Jain and Balakrishnan, 2012;Kennedy et al., 2014;Chitnis et al., 2020). For example, competition for resources may also drive signal partitioning as a by-product (Aldridge and Rautenbach, 1987;Norberg and Rayner, 1987;Kingston et al., 2000;Kingston and Rossiter, 2004;Siemers and Schnitzler, 2004;Kirschel et al., 2009b;Mancina et al., 2012;Krishnan and Tamma, 2016;Roemer et al., 2019). ...
Article
Full-text available
The diversity of animal acoustic signals has evolved due to multiple ecological processes, both biotic and abiotic. At the level of communities of signaling animals, these processes may lead to diverse outcomes, including partitioning of acoustic signals along multiple axes (divergent signal parameters, signaling locations, and timing). Acoustic data provides information on the organization, diversity and dynamics of an acoustic community, and thus enables study of ecological change and turnover in a non-intrusive way. In this review, we lay out how community bioacoustics (the study of acoustic community structure and dynamics), has value in ecological monitoring and conservation of diverse landscapes and taxa. First, we review the concepts of signal space, signal partitioning and their effects on the structure of acoustic communities. Next, we highlight how spatiotemporal ecological change is reflected in acoustic community structure, and the potential this presents in monitoring and conservation. As passive acoustic monitoring gains popularity worldwide, we propose that the analytical framework of community bioacoustics has promise in studying the response of entire suites of species (from insects to large whales) to rapid anthropogenic change.
... Acoustic signals play a key role in animal communication, such as in mate selection, resource defense, and individual or species recognition (Marler and Slabbekoorn, 2004;Wilkins et al., 2013). Acoustic signals are widely used for communication in birds (Mckown, 2008), and in the other animals, such as insects, frogs, bats, cetaceans, and primates (Ovaska and Caldbeck, 1997;Fedurek and Slocombe, 2011;Lin et al., 2016;Natasha et al., 2017;Schevill and Mcbride, 1956). ...
... Common kestrels emitted alarm calls when they encountered intruders or predators. Such calls in passerines and other birds signal the approach or presence of both airborne and terrestrial potential predators (Brown and Veltman, 1987;Klump and Curio, 1983;Marler and Slabbekoorn, 2004;Morton and Shalter, 1977). For example, alarm calls are used as a form of response to predators or intrusion by humans in the white-tailed hawk (Buteo albicaudatus) and northern goshawk (Accipiter gentilis) (Farquhar, 1993;Kennedy and Stahlecker, 1993). ...
Article
Full-text available
Acoustic signals play a key role in animal communication. Animals usually use alarm signals to warn mates or offspring of the presence of threats or to intimidate or distract predators. Birds commonly use acoustic signals as a means of communication. Alarm calls in passerines at different breeding stages can reflect their nest defense intensity. However, little is known about the characteristics, plasticity, and impact factors of alarm calls during the reproductive period in raptors. Here, from March to July in 2019, the alarm calls of eight pairs of common kestrels ( Falco tinnunculus ) during the breeding period were recorded using a portable recorder with a strongly directed microphone in the Zuojia Nature Reserve, Jilin province, China. The differences in acoustic parameters of parental alarm calls in different breeding stages were analyzed. The results showed that the alarm calls of common kestrels were composed of multi-harmonic arched frequency modulation with the maximum energy distribution in the second harmonic. The duration and rate of the alarm calls increased significantly as the breeding season progressed, showing that parents spent increasing amounts of time on nest defense. Additionally, the acoustic parameters of alarm calls in common kestrels were significantly different depending on offspring numbers, suggesting that offspring numbers influenced parental nest defense. These results showed that differences in alarm calls during different breeding stages may reflect a trade-off between defense costs and reproductive benefits.
... Bioacoustics-the study of animal sound-offers a fascinating window into animal behaviour, and also a valuable evidence source for monitoring biodiversity (Marler & Slabbekoorn, 2004;Laiolo, 2010;Marques et al., 2012;Brown & Riede, 2017). Bioacoustics has long benefited from computational analysis methods including signal processing, data mining and machine learning (Towsey et al., 2012;Ganchev, 2017). ...
... Many of the above taxa are important for biodiversity and conservation monitoring (including birds, bats, insects), or for comparative linguistics and behaviour studies (songbirds, cetaceans, primates, rodents). For some taxa, acoustic communication is a rich and complex part of their behaviour, and their vocalisations have a high complexity which is amenable to signal analysis (Marler & Slabbekoorn, 2004). On the other hand, progress is undeniably driven in part by practical considerations, such as the relative ease of recording terrestrial and diurnal species. ...
Article
Animal vocalisations and natural soundscapes are fascinating objects of study, and contain valuable evidence about animal behaviours, populations and ecosystems. They are studied in bioacoustics and ecoacoustics, with signal processing and analysis an important component. Computational bioacoustics has accelerated in recent decades due to the growth of affordable digital sound recording devices, and to huge progress in informatics such as big data, signal processing and machine learning. Methods are inherited from the wider field of deep learning, including speech and image processing. However, the tasks, demands and data characteristics are often different from those addressed in speech or music analysis. There remain unsolved problems, and tasks for which evidence is surely present in many acoustic signals, but not yet realised. In this paper I perform a review of the state of the art in deep learning for computational bioacoustics, aiming to clarify key concepts and identify and analyse knowledge gaps. Based on this, I offer a subjective but principled roadmap for computational bioacoustics with deep learning: topics that the community should aim to address, in order to make the most of future developments in AI and informatics, and to use audio data in answering zoological and ecological questions.
... The audio clips are then resampled to 22050 Hz with Librosa 0.6 audio processing package [16]. It has been reported that most birds vocalize in the frequency range of 0.5 kHz to 10 kHz [17]. The resampling is followed by peak normalisation. ...
... Inserting Eq. (16) and Eq. (17) in Eq. (4) holds ...
Preprint
The automatic classification of bird sounds is an ongoing research topic and several results have been reported for the classification of selected bird species. In this contribution we use an artificial neural network fed with pre-computed sound features to study the robustness of bird sound classification. We investigate in detail if and how classification results are dependent on the number of species and the selection of species in the subsets presented to the classifier. In more detail, a bag-of-birds approach is employed to randomly create balanced subsets of sounds from different species for repeated classification runs. The number of species present in each subset is varied between 10 and 300, randomly drawing sounds of species from a dataset of 659 bird species taken from Xeno-Canto database. We observe that the shallow artificial neural network trained on pre-computed sound features is able to classify the bird sounds relatively well. The classification performance is evaluated using several common measures such as precision, recall, accuracy, mean average precision and area under the receiver operator characteristics curve. All of these measures indicate a decrease in classification success as the number of species present in the subsets is increased. We analyze this dependence in detail and compare the computed results to an analytic explanation assuming dependencies for an idealized perfect classifier. Moreover, we observe that the classification performance depends on the individual composition of the subset and varies across 20 randomly drawn subsets.
... Sexual dichromatism is a form of sexual dimorphism that is widespread in birds; it refers to a difference in coloration between females and males (Badyaev & Hill, 2003). Males of many species show more brightly coloured plumage and sing more than females (Lovette & Fitzpatrick, 2016;Marler & Slabbekoorn, 2004). However, females of many other avian taxa also exhibit ornamented plumage and sing conspicuously (Langmore, 1998;Odom et al., 2014;Riebel et al., 2019). ...
... Differences in energy allocation to territorial response may translate into differences in energy allocation to egg incubation and rearing of offspring (Angelier and Chastel, 2009;Dittami et al., 1991). In T. ruficapillus and T. torquatus, sex roles may be more similar to oscine passerines of temperate zones, in which singing and territorial competition are predominantly male behaviours (Catchpole & Slater, 2008;Marler & Slabbekoorn, 2004). However, females of the Thamnophilus species still responded to the simulated intruders by singing, which is likely an ancestral condition in birds (Odom et al., 2014) and is typical in many Tyranni (suboscine) passerine species (Tobias et al., 2012a). ...
Article
Social selection, via intra- and intersexual competition for sexual (e.g. mates) and/or nonsexual (e.g. territories) resources, is thought to drive the evolution of ornaments in both sexes. However, the relative importance of intra- and intersexual competition in promoting the evolution of female and male ornamentation and, hence, sexual dichromatism remains poorly understood. We addressed this issue in antbirds (Thamnophilidae), a radiation of sexually dichromatic passerines wherein eumelanic plumage patches have evolved multiple times in both sexes. In antbirds, the degree of sexual dichromatism differs between closely related species primarily due to eumelanic dark patches in either sex. If eumelanic patches evolved by social selection, individuals of species bearing more conspicuous eumelanic patches should display stronger territorial responses regardless of their sex. Using playback experiments, we simulated three conspecific territorial intrusion types – a social pair, a female and a male – and measured responses by social pairs of two sister species pairs exhibiting greater interspecific differences in female coloration and one sister species pair exhibiting greater interspecific differences in male coloration. We found that females of species bearing more conspicuous eumelanic patches responded more strongly than females of species bearing less conspicuous eumelanic patches, but only towards simulated female and/or male intruders. However, males responded similarly to all intrusions regardless of interspecific coloration differences. Our results suggest that eumelanic patches in antbirds may function as ornaments and that greater female ornamentation may function in intra- and intersexual contexts and reflect stronger social competition in ornamented females for territories and, possibly, mates. In contrast, in species pairs with greater interspecific differences in male ornamentation, territorial competition may occur predominantly among males and female mate choice may drive the evolution of male ornamentation. Our study highlights that social selection pressures acting on both sexes may drive the evolution of contrasting sexual dichromatism patterns.
... This may include information about the individual's sex and identity, its reproductive status, the demarcation of its territory, and mainly, the species to which it belongs (Emlen 1972). Information in these realms can be encoded as differences in various acoustic features including syntactical structure, duration, rhythm, frequencies, and numbers of notes (Marler and Slabbekoorn 2004). With the exception of mimetic species, such as euphonias (Morton 1976) and mockingbirds (Gammon and Altizer 2011) that have repertoires including vocalizations from other species, most bird species have their own distinct vocal repertoires (Marler and Slabbekoorn 2004). ...
... Information in these realms can be encoded as differences in various acoustic features including syntactical structure, duration, rhythm, frequencies, and numbers of notes (Marler and Slabbekoorn 2004). With the exception of mimetic species, such as euphonias (Morton 1976) and mockingbirds (Gammon and Altizer 2011) that have repertoires including vocalizations from other species, most bird species have their own distinct vocal repertoires (Marler and Slabbekoorn 2004). This includes birds belonging to Parulidae (New World warblers), all of which have diagnostic vocalizations and in which species restricted to the Neotropics are not known to imitate other species. ...
Article
Most birds, including songbirds, produce distinct, species-specific songs and calls. Here, I report on an individual bird of the Neotropical warbler genus Myiothlypis that produced vocalizations typical of two congeneric species. The “bilingual” bird, observed in the Serra dos Cocais region of São Paulo state, Brazil, appeared visually to be a White-browed Warbler (Myiothlypis leucoblephara) but was documented emitting songs and calls of that species and of Flavescent Warbler (Myiothlypis flaveola). Two possible explanations, not mutually exclusive, are raised and discussed, i.e., (i) hybridization between the two species, previously undocumented, and (ii) vocal imitation of both species assimilated into its vocal repertoire.
... Note that the first two coefficients d 1 and d 2 of a tp , a f p and a f n have either the same values (up to the first eight digits, which are not shown here), or just differ in sign but not in value. These coefficients are shown in detail here since we will, in the following, demonstrate a connection between Equations (16)- (18) and the functions describing the dependence of the overall performance measures. Being able to describe a tp (n), a f p (n) and a f n (n), one can now attempt to understand the dependencies of the performance measures. ...
... This relation was numerically confirmed by comparing the coefficients for the polynomials describing A and a tp . The values of coefficients d 2 , d 1 , and c 0 are given after Equation (18). ...
Article
Full-text available
The automatic classification of bird sounds is an ongoing research topic, and several results have been reported for the classification of selected bird species. In this contribution, we use an artificial neural network fed with pre-computed sound features to study the robustness of bird sound classification. We investigate, in detail, if and how the classification results are dependent on the number of species and the selection of species in the subsets presented to the classifier. In more detail, a bag-of-birds approach is employed to randomly create balanced subsets of sounds from different species for repeated classification runs. The number of species present in each subset is varied between 10 and 300 by randomly drawing sounds of species from a dataset of 659 bird species taken from the Xeno-Canto database. We observed that the shallow artificial neural network trained on pre-computed sound features was able to classify the bird sounds. The quality of classifications were at least comparable to some previously reported results when the number of species allowed for a direct comparison. The classification performance is evaluated using several common measures, such as the precision, recall, accuracy, mean average precision, and area under the receiver operator characteristics curve. All of these measures indicate a decrease in classification success as the number of species present in the subsets is increased. We analyze this dependence in detail and compare the computed results to an analytic explanation assuming dependencies for an idealized perfect classifier. Moreover, we observe that the classification performance depended on the individual composition of the subset and varied across 20 randomly drawn subsets.
... Bioacoustics-the study of animal sound-offers a fascinating window into animal behaviour, and also a valuable evidence source for monitoring biodiversity (Marler and Slabbekoorn, 2004;Laiolo, 2010;Marques et al., 2012;Brown and Riede, 2017). Bioacoustics has long benefited from computational analysis methods including signal processing, data mining and machine learning (Towsey et al., 2012;Ganchev, 2017). ...
... Many of the above taxa are important for biodiversity and conservation monitoring (including birds, bats, insects), or for comparative linguistics and behaviour studies (songbirds, cetaceans, primates, rodents). For some taxa, acoustic communication is a rich and complex part of their behaviour, and their vocalisations have a high complexity which is amenable to signal analysis (Marler and Slabbekoorn, 2004). On the other hand, progress is undeniably driven in part by practical considerations, such as the relative ease of recording terrestrial and diurnal species. ...
Preprint
Full-text available
Animal vocalisations and natural soundscapes are fascinating objects of study, and contain valuable evidence about animal behaviours, populations and ecosystems. They are studied in bioacoustics and ecoacoustics, with signal processing and analysis an important component. Computational bioacoustics has accelerated in recent decades due to the growth of affordable digital sound recording devices, and to huge progress in informatics such as big data, signal processing and machine learning. Methods are inherited from the wider field of deep learning, including speech and image processing. However, the tasks, demands and data characteristics are often different from those addressed in speech or music analysis. There remain unsolved problems, and tasks for which evidence is surely present in many acoustic signals, but not yet realised. In this paper I perform a review of the state of the art in deep learning for computational bioacoustics, aiming to clarify key concepts and identify and analyse knowledge gaps. Based on this, I offer a subjective but principled roadmap for computational bioacoustics with deep learning: topics that the community should aim to address, in order to make the most of future developments in AI and informatics, and to use audio data in answering zoological and ecological questions.
... Birdsong plays an important role in the acquisition of breeding resources, to mediate social conflicts and to attract mates (Catchpole and Slater 2008;Marler and Slabbekoorn 2004) but also for pair coordination and in alarm situations (Cresswell 1994;Halkin 1997). ...
Preprint
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The blue tit ( Cyanistes caeruleus ) is an important avian model in evolutionary ecology (> 20,000 published scientific studies). Song, like in other songbird species, is generally described as a male trait and plays an important role in mate attraction and territory defence. Over the decades, there have been recurring reports of anecdotal female song but these have not led to any quantitative study of female song in blue tits. Our systematic sampling over three years revealed prolific female singing in a northern population of colour ringed blue tits. Daytime singing of females occurred throughout the breeding season during agonistic interactions, solo songs and alarm situations, and these contexts are similar to male song. Notably, female song was absent during the dawn chorus; the period around sunrise when males sing intensively just before mating. Female and male song overlapped substantially in acoustic structure (i.e. same song types, peak frequency or trill rates) but there were also significant differences in that females had smaller repertoires, shorter trills and lower vocal consistency. Differential selections pressures related with contextual (functional) differences in the role of male and female song could explain the observed differences in acoustic structure. The new finding of prolific female singing in such a well-studied species suggests we ought to revise our understanding of male and female vocal communication in this (and probably other) species. Identifying the selection pressures associated to the convergence versus divergence of male and female song may provide important insight in understanding birdsong evolution. Lay summary Female song has been anecdotally reported in blue tits but there are no quantitative studies of singing behaviour, song structure or context. Here, we report frequent female singing in blue tits, associated mostly with agonistic interactions and alarm situations. Importantly, female song was not observed during dawn chorus, the period around sunrise when males sing intensively just before mating. Female and male song overlapped substantially in acoustic structure (i.e. same song types) but there were also significant differences (i.e. females sang with lower vocal consistency). We speculate that differences in context (function) of male and female song could explain the observed differences in acoustic structure. The new finding of prolific female singing in such a well-studied species suggests we ought to revise our understanding of male and female vocal communication.
... However, such methods based on separated counts remain limited. Even relatively simple systems such as bird songs can be highly combinatorial: groups of notes form syllables which are themselves assembled into phrases that are then grouped into songs, and these different subunits can appear in various combinations at multiple levels [48]. Instead of separately quantifying connectedness, modularity and nestedness, we may royalsocietypublishing.org/journal/rsos R. Soc. ...
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While there is no consensus about the definition of complexity, it is widely accepted that the ability to produce uncertainty is the most prominent characteristic of complex systems. We introduce new metrics that purport to quantify the complexity of living organisms and social organizations based on their levels of uncertainty. We consider three major dimensions regarding complexity: diversity based on the number of system elements and the number of categories of these elements; flexibility which bears upon variations in the elements; and combinability which refers to the patterns of connection between elements. These three dimensions are quantified using Shannon's uncertainty formula, and they can be integrated to provide a tripartite complexity index. We provide a calculation example that illustrates the use of these indices for comparing the complexity of different social systems. These indices distinguish themselves by a theoretical basis grounded on the amount of uncertainty, and the requirement that several aspects of the systems be accounted for to compare their degree of complexity. We expect that these new complexity indices will encourage research programmes aiming to compare the complexity levels of systems belonging to different realms.
... The diversity and variability in these vocalizations serve several functional roles in foraging (Boogert, Giraldeau, & Lefebvre, 2008), attracting a mate (Byers & Kroodsma, 2009), and warning against predators (Demartsev et al., 2014). Each type of vocalization is unique and usually consists of a sequential order of notes, which vary in structure (frequency, duration, energy, pace, and intensity) and the number of repetitions (Marler & Slabbekoorn, 2004). Variation in notes gives rise to complexity, which is common in the songs of Passeriform birds and is of interest to ecologists and evolutionary biologists. ...
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Birdsong is an important signal in mate attraction and territorial defense. Quantifying the complexity of these songs can shed light on individual fitness, sexual selection, and behavior. Several techniques have been used to quantify song complexity and be broadly categorized into diversity indices, measures of stationary probabilities, and measures of sequential variations. However, these methods are unable to account for important acoustic features like the frequency bandwidth and the variety in the shape of syllables which are an integral part of these vocal signals. This study proposes a new complexity measure that considers intra-song note variability and calculates a weighted index for birdsongs using spectral cross-correlation. We compared the previously described methods to understand the advantages and limitations based on the factors that would be affecting the complexity of songs. We developed a new method- Note Variability Index (NVI), which incorporates the spectral features of notes while quantifying complexity. This measure alleviates the need for manual annotations of notes that can be error-prone. We used Spectrogram Cross-Correlation (SPCC) to compare notes within a song and used the output values to quantify song complexity. To check for the efficacy of the new method, we generated synthetic songs to caricature extremes in song complexity and compared selected conventional complexity measures along with the NVI. We provide case-specific limitations of these methods. Additionally, to examine the efficacy of this new method in real-world scenarios, we used natural birdsongs from multiple species across the globe with varying song structures to compare conventional methods with NVI. To our knowledge, NVI is the only song complexity method that captures the variation of spectral features of notes in songs where the conventional methods fail to distinguish between similar song structures with different note types. As NVI does not need a manual classification of notes, it can be easily implemented for any type of birdsong with existing sound analysis softwares; it is very quick, avoids the possible biases in note classification, and can possibly be automated for large datasets in the future.
... In intrasexual competition, animals may respond to simulated intruders by calling in antiphony or by pausing the calling activity, sometimes reorienting their head and body toward the source of the sound or performing positive phonotaxis (Wingfield and Lewis 1993;Narins et al. 2003;Hayes et al. 2004;Giasson and Haddad 2006;Morais et al. 2015). Moreover, as a part of territorial defense, many individuals also address aggressive or altered advertisement calls toward rivals (Cheney and Seyfarth 1996;Marler and Slabbekoorn 2004;Wells 2007;Moseley et al. 2013;Toledo et al. 2015). Such acoustic modifications are generally elicited by close-range interactions among anurans, as a response from residents to intruders (Toledo et al. 2015). ...
Article
Spectral properties of animal acoustic signals may help individuals to assess the characteristics of rivals and to adjust their competitive strategies in territorial disputes. Thus, we hypothesized that the distribution of energy across frequency bands in anuran calls determines behavioral responses in male-male competition. Using playback experiments, we investigated the relevance of the harmonic calls in the acoustic communication of the treefrog Dendropsophus minutus. We exposed territorial males to three synthetic acoustic stimuli composed of aggressive notes: 1) standard call (all harmonics and peak frequency corresponding to the second band); 2) inverted-energy call (all harmonics and peak frequency corresponding to the first band); and 3) concentrated-energy call (all energy contained in the second harmonic). Males responded aggressively to all stimuli, mainly by increasing the rate and duration of their aggressive notes. However, when exposed to stimuli with different harmonic configurations, males changed the harmonic structure of their own calls, emitting more A-and B-notes with peak power in the fundamental frequency, particularly when exposed to the concentrated-energy call. Our results suggest that male frogs may use the harmonic structure of calls to assess opponents and modulate territorial and aggressive behavior, triggering complex acoustic adjustments. This study contributes to our knowledge about the functions of acoustic traits in amphibian social interactions, and particularly of the presence of harmonics that has received less attention compared to other acoustic properties in the study of animal acoustic communication.
... At the most basic level, comparing acoustic structure across taxa requires identifying and defining the type of acoustic signals to be compared. This requires some familiarity with the organisms being studied, because most animals produce multiple sounds that are structurally and functionally distinct (Gerhardt & Huber 2002;Marler & Slabbekoorn, 2004;Catchpole & Slater, 2008;Cardoso, 2012;Cholewiak et al., 2013;Russo & Voigt, 2016;Smotherman et al., 2016). The broadest acoustic unit that will be compared is usually dictated by the research question (e.g. ...
Article
Animals produce a wide array of sounds with highly variable acoustic structures. It is possible to understand the causes and consequences of this variation across taxa with phylogenetic comparative analyses. Acoustic and evolutionary analyses are rapidly increasing in sophistication such that choosing appropriate acoustic and evolutionary approaches is increasingly difficult. However, the correct choice of analysis can have profound effects on output and evolutionary inferences. Here, we identify and address some of the challenges for this growing field by providing a roadmap for quantifying and comparing sound in a phylogenetic context for researchers with a broad range of scientific backgrounds. Sound, as a continuous, multidimensional trait can be particularly challenging to measure because it can be hard to identify variables that can be compared across taxa and it is also no small feat to process and analyse the resulting high-dimensional acoustic data using approaches that are appropriate for subsequent evolutionary analysis. Additionally, terminological inconsistencies and the role of learning in the development of acoustic traits need to be considered. Phylogenetic comparative analyses also have their own sets of caveats to consider. We provide a set of recommendations for delimiting acoustic signals into discrete, comparable acoustic units. We also present a three-stage workflow for extracting relevant acoustic data, including options for multivariate analyses and dimensionality reduction that is compatible with phylogenetic comparative analysis. We then summarize available phylogenetic comparative approaches and how they have been used in comparative bioacoustics, and address the limitations of comparative analyses with behavioural data. Lastly, we recommend how to apply these methods to acoustic data across a range of study systems. In this way, we provide an integrated framework to aid in quantitative analysis of cross-taxa variation in animal sounds for comparative phylogenetic analysis. In addition, we advocate the standardization of acoustic terminology across disciplines and taxa, adoption of automated methods for acoustic feature extraction, and establishment of strong data archival practices for acoustic recordings and data analyses. Combining such practices with our proposed workflow will greatly advance the reproducibility, biological interpretation, and longevity of comparative bioacoustic studies.
... For instance, in red deer (Cervus elaphus), females are preferentially attracted by high roaring rate and lowpitched roars, emitted by large males, which have a better reproductive success than small males (Reby et al. 2010). In several songbird species, females are more attracted by males singing with a high song rate, which have a better territory quality, body condition, or feeding rate, and thus a higher reproductive success (reviewed in Marler and Slabbekoorn 2004). ...
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In blue petrels (Halobaena caerulea), females are supposed to be particularly choosy and mate choice can take a couple of years. In these lifelong monogamous seabirds, choosing a good mate is crucial and has a strong influence on their fitness. Due to their nocturnal habits, the absence of sexual dimorphism, and the physical barrier between males calling from their burrow and females flying above the colony, vocal signals seem to be one of the main channels for males to communicate with potential mates. In a previous study, we investigated whether acoustic parameters of male calls carry information about morphological characteristics that might be indicators of males’ qualities. Here, we experimentally test whether these acoustic parameters linked to male characteristics are actually attractive to females. To do so, we played back modified calls of males to females in a colony of blue petrels of the Kerguelen archipelago. We found that flying females were more attracted by high-pitched calls, and by calls broadcasted at a high call rate. Previous studies showed a relationship between pitch and bill depth and length. In filter-feeding birds, such as blue petrels, bill morphology influences feeding efficiency. A high call rate is an indicator of sexual motivation and makes the caller easier to locate by potential mates and predators in the hubbub of the colony. We thus hypothesized that producing frequent high-pitched calls appeared to be preferable for a conspicuous sexual signaling although it may increase predation risks. Significance statement Mate selection process is largely unknown in burrowing petrels due to their cryptic life at the colony. Here, we examined the implication of vocal signals in mate choice in the blue petrel Halobaena caerulea. We used an experimental setting based on a two-choice test to show that male calls are sexual signals attracting females. As expected, broadcasting male calls attracted females. Despite the apparent stereotypy of male calls, their acoustic parameters transmit pieces of information that may influence females’ preference. We found that females are more attracted by high call rate and high-pitched calls. This is the first evidence of the implication and influence of vocal signals in mate choice in burrowing petrels.
... The "songs" of songbirds, for example, are complex patterns of vocalized sounds with roles in territorial marking and mate attraction. As a biocultural system making up a cultural kind, these songs comprise an intergenerational, social pedagogy, a sonic medium, distinctive combinatorial structures in their design, and a dedicated biological substrate in the birds' bodies and brains that enables their learning, production, and cognitive processing (Beecher and Burt 2004, Marler and Slabberkoorn 2004, Nottebohm 2005, Fiete and Seung 2009). These join together to make birdsong coherent and autonomous from other bird behaviors, and this systemic assemblage enables the songs to fulfill the functions that have evolved in their selective histories. ...
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Two welcome extensions of evolutionary thinking have come to prominence over the last thirty years: the so-called "extended evolutionary synthesis" (EES) and debate about biological kinds and individuals. These two agendas have, however, remained orthogonal to one another. The EES has mostly restricted itself to widening the explanations of adaptation offered by the preceding "modern evolutionary synthesis" by including additional mechanisms of inheritance and variation; while discussion of biological kinds has turned toward philosophical questions of essential vs. contingent properties of life forms and realist vs. epistemological approaches to categorization and classification. Here we attempt to broaden the explanatory scope of evolutionary theory by linking these two agendas. We expand on the mechanistic orientation of the EES, using new understandings of networked systems of components in order to engage the distinct intellectual challenge of the origination of historical kinds. With this phrase we designate a subset of natural kinds that acquires, through evolutionary processes, a quasi-independent lineage-history. Such kinds emerge in both biology and culture, and we enlarge the limited number of historical kinds that have thus far been recognized in evolutionary biology in a series of paradigmatic exemplars, from genes and cell types to rituals and music. For each exemplar we discern specific mechanisms by which it arose and persists; comparing these, we suggest a general unity in the ways in which diverse historical kinds originate.
... Words vary in acoustic parameters but information is still conveyed. Variations in time-frequency domains in the acoustic communication signals by humans and other species can also convey additional important information associated to -for example -individual identity, group membership, sex, age, emotional state, and physiological state (e.g., Marler and Slabbekoorn, 2004;Dellwo et al., 2007;Pell et al., 2009;Khanna and Sasikumar, 2011;Briefer, 2012). In light of not possessing a Rosetta Stone or a cryptographer's crib to aid us in deciphering how information is encoded in dolphin whistled communication, we propose that a deeper exploration of how information can be encoded in whistle form as evidenced in human whistle languages may provide important insights to inform the analysis of dolphin whistles. ...
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Humans use whistled communications, the most elaborate of which are commonly called “whistled languages” or “whistled speech” because they consist of a natural type of speech. The principle of whistled speech is straightforward: people articulate words while whistling and thereby transform spoken utterances by simplifying them, syllable by syllable, into whistled melodies. One of the most striking aspects of this whistled transformation of words is that it remains intelligible to trained speakers, despite a reduced acoustic channel to convey meaning. It constitutes a natural traditional means of telecommunication that permits spoken communication at long distances in a large diversity of languages of the world. Historically, birdsong has been used as a model for vocal learning and language. But conversely, human whistled languages can serve as a model for elucidating how information may be encoded in dolphin whistle communication. In this paper, we elucidate the reasons why human whistled speech and dolphin whistles are interesting to compare. Both are characterized by similar acoustic parameters and serve a common purpose of long distance communication in natural surroundings in two large brained social species. Moreover, their differences – e.g., how they are produced, the dynamics of the whistles, and the types of information they convey – are not barriers to such a comparison. On the contrary, by exploring the structure and attributes found across human whistle languages, we highlight that they can provide an important model as to how complex information is and can be encoded in what appears at first sight to be simple whistled modulated signals. Observing details, such as processes of segmentation and coarticulation, in whistled speech can serve to advance and inform the development of new approaches for the analysis of whistle repertoires of dolphins, and eventually other species. Human whistled languages and dolphin whistles could serve as complementary test benches for the development of new methodologies and algorithms for decoding whistled communication signals by providing new perspectives on how information may be encoded structurally and organizationally.
... However, such methods based on separated counts remain limited. Even relatively simple systems such as bird songs can be highly combinatorial: groups of notes form syllables which are themselves assembled into phrases that are then grouped into songs, and these different subunits can appear in various combinations at multiple levels (Marler and Slabbekoorn, 2004). Instead of separately quantifying connectedness, modularity and nestedness, we may consider complex systems as sets of subunits which can vary in their degree of dissociation and differentiation, as well as in the interactions that link the units composing them. ...
Thesis
The social complexity hypothesis posits that living in a complex social system requires complex communication skills. Complexity and uncertainty being linked, I have tested this hypothesis by comparing several primate species that differ by the degree of uncertainty of their social interactions. First, I elaborated tools to measure three components of system complexity (diversity, flexibility, combinability). I developed a procedure to objectively assess diversity and flexibility using clustering algorithms.Then, I used this method to study the vocalisations emitted by adult females in four species of macaques: two tolerant species (Tonkean & crested macaques) and two intolerant species (Japanese & rhesus macaques). I found marked contrasts between these two pairs of species in terms of diversity and flexibility of vocal signals, with different degrees of freedom in the association between acoustic structure and context depending on the species. These results support the social complexity hypothesis by showing that animals that experience more uncertain social interactions also show a greater richness of communication signals.
... Given that mixed-species signaling aggregations are common across taxa (e.g. dawn choruses of birds and mixed-species choruses of frogs or insects, including hybrid zones; Sueur 2002;Stensland et al. 2003;Marler & Slabbekoorn 2004;Phelps et al. 2007;Sridhar et al. 2009;Wells 2010;Römer 2013;Trillo et al. 2017), interactions with heterospecifics are likely important mechanisms modulating eavesdropper pressure, and thereby influencing signal evolution, signaling behavior, and the distribution of species within and between signaling aggregations. ...
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Males often broadcast conspicuous signals from within mixed-species aggregations to attract mates. In addition to attracting females, however, these displays expose signalers to eavesdropping predators and parasites. For individuals in mixed-species aggregations, the balance between attracting mates and avoiding eavesdroppers is influenced both by the attractiveness of their calls and by the calling activity of conspecific and heterospecific neighbors. Through a process termed “collateral damage”, frogs signaling near heterospecific neighbors that are highly attractive to eavesdroppers can experience drastically increased parasitism compared to those signaling next to conspecifics. Here, we investigate whether the intensity of this collateral damage is influenced by the density of, or the call types produced by, heterospecific neighbors. In phonotaxis trials using hourglass treefrogs as the focal species and túngara frogs as the attractive heterospecific neighbor, we found no differences in the number of parasites attracted to hourglass treefrog calls played adjacent to simple versus complex túngara calls. By contrast, a higher density of neighboring túngara frogs decreased the collateral damage suffered by hourglass treefrogs by approximately 40%. Our results demonstrate that the density of nearby heterospecifics can modulate parasitism risk due to collateral damage in mixed-species aggregations. Thus, our conception of the dilution of eavesdropper risks with increasing group size may need to be augmented to include the effects of multiple prey or host types. HIGHLIGHTS ● Heterospecific call type does not change collateral damage on hourglass treefrogs ● However, parasitism decreases when calling next to high densities of heterospecifics
... In analyzing vocalizations of birds, two-dimensional Fourier power spectra (sonograms) have been widely used (e.g. Marler and Slabbekoorn 2004). STFT is usually used to construct two-dimensional spectra. ...
Preprint
In Kato and Uemura (2012), we introduced the Least Absolute Shrinkage and Selection Operator (Lasso) method, a kind of sparse modeling, to study frequency structures of variable stars. A very high frequency resolution was achieved compared to traditional Fourier-type frequency analysis. This method has been extended to two-dimensional frequency analysis to obtain dynamic spectra. This two-dimensional Lasso frequency analysis yielded a wide range of results including separation of the orbital, superhump and negative superhump signals in Kepler data of SU UMa stars. In this paper, I briefly reviewed the progress and applications of this method. I present a full R code with examples of its usage. This code has been confirmed to detect the appearance of the orbital signal and the variation of the spin period after the eruption of the nova V1674 Her. This code also can be used in multidisciplinary purposes and I provide applications to analysis of avian vocalizations. I found fine structures in the call of the Eurasian wren ($\textit{Troglodytes troglodytes}$), which is likely to be used species identification. This code would be a new tool in studying avian vocalizations with high temporal and frequency resolutions. Interpretations of the power spectra of avian vocalizations will also be helpful in interpreting the power spectra of variable stars.
... Finally, the original function of mimetic elements for the model species was scored as (1) 'song', (2) 'alarm call' or (3) 'other'. We defined 'songs' broadly as conspicuous 'advertisement' vocalizations that mediate inter-and intrasexual interactions, and 'alarm calls', including 'flee' and 'mobbing' alarm calls, as sounds that function in predator defence (Marler, 2004). Our three categories could be applied across model species. ...
Article
Mimicry has long been a focus of research, but little is known about how and why many species of bird incorporate imitations of heterospecific sounds into their vocal displays. Crucial to understanding mimetic song is determining what sounds are mimicked and in what contexts such mimicry is produced. The superb lyrebird, Menura novaehollandiae, is a large oscine passerine with a lek-like mating system. Both sexes are accurate and versatile vocal mimics of the vocalizations of other species, but little is known about how males deploy their repertoire of mimicked sounds across contexts. Using extended focal watches, we recorded adult males displaying during the breeding season. We found that males mimicked heterospecific songs and nonalarm calls during ‘recital’ displays usually performed while they were perched and visually inconspicuous. In contrast, during visually conspicuous ‘dance’ displays, commonly performed on display mounds, males only mimicked heterospecific alarm calls. While much rarer than recital displays, dance displays were associated with the final stages of mate choice preceding copulation. These results provide the first evidence of any species varying its repertoire of mimicked sounds with different sexual contexts. Previous work suggests that mimicry in dance displays functions deceptively to manipulate the antipredator responses of females during the final stages of courtship. However, the structure and context of recital mimicry closely resembles the sexual advertisement song performed by nonmimicking songbirds. Given the importance of mimicry in the acoustic ecology of lyrebirds, our results suggest that with recital song males advertise the quality of their mimicry as it likely benefits both male and female offspring. Our finding that male superb lyrebirds mimic functionally distinct heterospecific vocalizations during different modes of courtship suggests that the evolution and maintenance of avian vocal displays are more complex than previously thought.
... Based on our observations, males sing more in the morning hours (6:00 to 10:00 a.m.) than the rest of the day. According to a review of the literature, several bird species sing their songs loudest around dawn, according to the acoustic transmission hypothesis, because this is the time of day when songs are least degraded by environmental noises and hence travel the greatest distances (Henwood and Fabrick, 1979;Dabelsteen and Mathevan, 2002;Marler and Slabbekoorn, 2004). Males were found foraging together, sharing social relationships with other flocks while communal roosting and foraging in winter. ...
Article
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Present study was aimed to document the breeding behaviour of the Eurasian Magpie Pica pica bactriana from Ladakh. Information is scanty on the nesting and reproductive biology of this species in Ladakh. Field work was carried out from March 2019 to May 2021 at two study locations in the Kargil area of Ladakh. Breeding season of Eurasian Magpie is started from early March to May. Pairing in adult individuals occur during winter flocking, which begins with heavy snowfall and lasts till the end of February. The average pre-nesting period was around four weeks (mean: 24.87±0.83 days). The courtship displays and mate acquisition rituals of the Eurasian Magpie are comprised of both vocalizations and physical displays. Analysis of the data revealed that shrub fragments, leaves, grasses, clay and occasionally electric wire trash were used to construct the nest. In a clutch, the female lays 4-5 eggs (mean: 3.89±0.85 eggs). The eggs were incubated by the female individual, and the nest was guarded by the male. Average incubation period was 20.50±0.73 days. Both sexes took part in parental chores. The fledgling period was around four weeks (mean: 26.8±0.74 days).
... The visual responsiveness of the visual cortex neurons in kittens develops during different sensitive phases: binocular stereopsis develops during 3 to 15 weeks after birth, whereas orientation selectivity develops during 6 to 12 weeks 57-60 . Songbirds learn to sing conspecific songs during several phases of proficiency during development 61 . For example, zebra finches can produce sound elements of a model song by 65 days of age and can sing the precise order of these elements by 90 days of age 62 . ...
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Behavioral laterality—typically represented by human handedness—is widely observed among animals. However, how laterality is acquired during development remains largely unknown. Here, we examined the effect of behavioral experience on the acquisition of lateralized predation at different developmental stages of the scale-eating cichlid fish Perissodus microlepis. Naïve juvenile fish without previous scale-eating experience showed motivated attacks on prey goldfish and an innate attack side preference. Following short-term predation experience, naïve juveniles learned a pronounced lateralized attack using their slightly skewed mouth morphology, and improved the velocity and amplitude of body flexion to succeed in foraging scales during dominant-side attack. Naïve young fish, however, did not improve the dynamics of flexion movement, but progressively developed attack side preference and speed to approach the prey through predation experience. Thus, the cichlid learns different aspects of predation behavior at different developmental stages. In contrast, naïve adults lost the inherent laterality, and they neither developed the lateralized motions nor increased their success rate of predation, indicating that they missed appropriate learning opportunities for scale-eating skills. Therefore, we conclude that behavioral laterality of the cichlid fish requires the integration of genetic basis and behavioral experiences during early developmental stages, immediately after they start scale-eating.
... Finally, changes in the quality of a broadcast vocalization can have significant impact on the birds' response. Several species respond more aggressively to playbacks of clear vs. degraded vocalizations broadcast at the same amplitude (Richards 1981, McGregor et al. 1983, McGregor & Krebs 1984, Slabbekoorn 2004. ...
Article
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Acoustic playback is commonly used to study wild birds, with applications as diverse as investigating behaviours, ascertaining the presence of rare and elusive species, and attracting individuals to a location. The number of studies employing playback is growing larger every year because it is easy to apply, increasingly affordable and very effective. However, the way that it is used and reported varies significantly across researchers and species. This lack of a protocol for reporting acoustic playbacks inevitably slows the progress of the field, as studies cannot be easily compared. In 1991, some of the most knowledgeable researchers in the field of animal communication met at a North Atlantic Treaty Organization (NATO) Advanced Research Workshop (ARW) at Thornbridge Hall in the UK to consider the design of playback experiments. The proceedings of the meeting were published in 1992 and contain crucial guidelines regarding this use of playback. In this paper we review the literature for papers published since that milestone that use acoustic playback in ornithological fieldwork contexts. We use the RepOrting standards for Systematic Evidence Syntheses (ROSES) to evaluate the description of the methods used. The main goal of this review paper is to identify a shared set of rules for employing and reporting the playback technique in such contexts to promote reproducibility and comparability. We found 625 peer-reviewed articles in three on-line databases, of which 419 reported field (rather than captive) studies employing avian playback. The biggest hindrance to reproducibility is the availability of the acoustic tracks used by authors; 4% (15 articles) of our sample made their tracks publicly available. We found that only one article provided enough details for their playback application to be fully reproducible. Further, only five articles (0.92%) provided enough information for reproducibility, even if we assume information about track preparation and recording details to be unnecessary when tracks are available. Based on our synthesis of the literature, we provide a set of recommendations for the reporting of playback uses to promote reproducibility, including sample paragraphs of description as supplementary material. We strongly recommend that tracks used for such experiments are deposited in dedicated on-line repositories for the use of other researchers. While our focus is avian fieldwork applications of the playback technique, we believe that our findings can be easily transferred to other animal systems subject to acoustic playback.
... Almost two centuries after Barrington's original findings, groundbreaking work from the likes of William Thorpe, Peter Marler, Mark Konishi, and others laid the foundation for our current understanding of how song is learned, its potential capacity limits, and what mediates singing in passerine songbirds (Marler and Slabbekoorn, 2004). However, studies of song learning and development have primarily been focused on male songbirds as there were assumed male biased sex-based differences (i.e. ...
Article
In many species, male and female animals differ in the types and frequency of particular behaviors (e.g. reproductive behavior, parental behavior, etc.). These differences in behavior are quite often related to the neural and hormonal control of said behaviors. In the temperate zone it is commonly stated that male songbirds sing much more frequently and with much greater quality compared to their female counterparts. However, recent evidence has called these claims into question (Odom et al., 2014; Price et al., 2008; Webb et al., 2016). That said, neuroendocrine studies of song behavior have primarily focused on male birds and relatively little work has been done exclusively or comparatively with female songbirds. What we do know, however, is that there is wide variability in the vocal ability and capacity of female songbirds and that there is a developmental link between the hormonal milieu and neuro-social development that facilitate these behavioral phenotypes. Both testosterone and estradiol have been demonstrated to play pivotal roles in behavioral and neural differentiation of male and female song behavior profiles. Here we review a brief history of empirical investigation into steroid regulation of song in female birds, including the pattern of song activation, constraints on the ability of testosterone to induce singing, and the role of the anterior forebrain in supporting song learning. We conclude with a brief analysis of a major gap in the field's knowledge regarding naturally occurring female song and the neuroendocrine underpinnings of a socially salient learned behavior ripe for systematic investigation.
... Vocal communication of animals has two main components: signallers emit acoustic signals, and receivers perceive them and process the information content of the signals (Maynard Smith and Harper 2003;Bradbury and Vehrencamp 2011). Many avian lineages evolved fine-tuned acoustic communication systems and have a great variety of auditory signals for several functions, including songs (Catchpole and Slater 2008) and/or calls (Marler 2004). Oscine birds (Passeriformes), parrots (Psittaciformes), and hummingbirds (Trochilliformes) are able to learn acoustic elements from parents and neighbours, or even imitate different species (Kroodsma and Miller 1982). ...
Article
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The obligate brood parasitic common cuckoo (Cuculus canorus) is best known for its two-note “cu-coo” call, which is uttered repeatedly by adult males during the breeding season. This call advertises the male’s claim for his territory. A rare, aberrant version (“cu-kee”) was discovered in a population of cuckoos in central Hungary. In a playback experiment, we simulated conspecific territorial intrusions using either aberrant call sequences or normal calls (as control). Cuckoos responded to both calls similarly by approaching the speaker, flying around it several times, and perching on nearby trees. To identify the role of each note of these cuckoo calls, we also played sequences of the first (“cu”) or second (“coo” or “kee”) notes of the calls. Territorial males responded to first notes at similarly high frequencies as to each of the full calls, whereas responses toward either second note type were nearly absent. Thus, the first notes of both typical and aberrant cuckoo calls contain sufficient information to recognize conspecific males and the novel calls did not reduce the efficiency of male-male communication in cuckoos because the aberration occurred in the less functional second note. Significance statement Birds use songs and calls to communicate with each other, including advertising their territories to keep competitors away. However, when the acoustic signal is atypical and distorted, the receiver individual may not process it correctly. Common cuckoos recognize a territorial intruder by their well-known “cu-coo” calls. We studied a rare, aberrant version of the common cuckoo call (“cu-kee”), which differed from the normal call in the second note of the two-partite call. However, cuckoos responded similarly to both of the normal and aberrant calls in a playback experiment. When the first or second parts of the different calls were played separately, only the first part of the cuckoo calls was effective in eliciting territorial defence. Consequently, the aberrant second note did not reduce cuckoos’ communication efficiency.
... The diversity and variability in these vocalizations serve several functional roles in foraging (Boogert et al., 2008), attracting a mate and defending territories (Catchpole, 1987;Kroodsma & Byers, 1991), and warning against predators (Demartsev et al., 2014). Each type of vocalization is unique and usually consists of a sequential order of notes, which vary in spectral properties (frequency, duration, energy, pace and intensity) and the number of repetitions (Marler & Slabbekoorn, 2004). This order of the notes (sequence) and the spectral variation in notes (diversity) gives rise to the song complexity. ...
Article
Birdsong is an important signal in mate attraction and territorial defense. Quantifying the complexity of these songs can shed light on individual fitness, sexual selection, and behavior. Several techniques have been used to quantify song complexity and be broadly categorized into measures of sequential variations and measures of diversity. However, these methods are unable to account for important acoustic features like the frequency bandwidth and the variety in the spectro‐temporal shape of notes which are an integral part of these vocal signals. This study proposes a new complexity method that considers intra‐song note variability and calculates a weighted index for birdsongs using spectral cross‐correlation. We first compared previously described methods to understand their advantages and limitations based on the factors that would affect the complexity of songs. We then developed a new method‐ Note Variability Index (NVI), which incorporates the spectral features of notes to quantify complexity. This method alleviates the need for manual classification of notes that can be error‐prone. We used Spectrogram Cross‐Correlation (SPCC) to compare notes within a song and used the output values to quantify song complexity. To evaluate the efficacy of the new method, we generated synthetic songs to caricature extremes in song complexity and compared selected conventional complexity methods along with the NVI. We provide case‐specific limitations of these methods. Additionally, to examine the efficacy of this new method in real‐world scenarios, we used natural birdsongs from multiple species across the globe with varying song structures to compare conventional methods with NVI. To our knowledge, NVI is the only song complexity method that captures the variation of spectral‐temporal shapes of the notes in songs where the conventional methods fail to distinguish between similar song structures with different note types. Furthermore, as NVI does not need a manual classification of notes, it can be easily implemented for any type of birdsong with existing sound analysis software; it is quick, avoids the possible subjectivity in note classification, and can be automated for large datasets.
... Calls linked with specific behaviours had distinctive acoustic features. In birds, structured, stereotypic calls are commonly used for standard behavioural responses, whereas graded signals, with more varying shape, are used in more subtle social contexts (Marler 2004). In Great Cormorants, there was a large proportion of stereotypic vocalizations associated with a particular behaviour. ...
... Coordination of group activity and information on the location and identity of group members can be mediated by signaling. Many species of birds and mammals maintain contact by acoustic signaling, emitting separation or contact calls (Marler 2004;Kondo and Watanabe 2009;Fichtel and Manser 2010). Reunions in fission-fusion social systems also commonly involve greeting displays in some mammals and birds that facilitate recognition, expression of intention and mutual affiliation, reassurance, or assessment (Bradbury and Vehrencamp 2011). ...
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Communication between group members is mediated by a diverse range of signals. Contact calls are produced by many species of birds and mammals to maintain group cohesion and associations among individuals. Contact calls in bats are typically relatively low-frequency social calls, produced only for communication. However, echolocation calls (higher in frequency and used primarily for orientation and prey detection) can also facilitate interaction among individuals and location of conspecifics in the roost. We studied calling behaviour of brown long-eared bats ( Plecotus auritus ) during return to maternity roosts in response to playbacks of social and echolocation calls. We hypothesised that calling by conspecifics would elicit responses in colony members. Bat responses (inspection flights and social calls production) were significantly highest during social call and echolocation call playbacks than during noise (control) playbacks. We suggest that social calling in maternity roosts of brown long-eared bat evolved to maintain associations among roostmates, rather than to find roosts or roostmates, because this species is strongly faithful to roosts and the social groups and roosts are stable over time and space. Living in a stable social group requires recognition of group members and affiliation of social bonds with group members, features that may be mediated by vocal signals.
... However, the detailed neural molecular mechanisms underlying species-specific learned behaviors have not been fully clarified. To tackle this issue, oscine songbirds have been used as a salient model system owing to their unique song-learning ability, which is species-specifically regulated through conserved neural circuits, called song circuits, for song learning and production [1,[6][7][8][9]. ...
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Songbirds are one of the few animal taxa that possess vocal learning abilities. Different species of songbirds exhibit species-specific learning programs during song acquisition. Songbirds with open-ended vocal learning capacity, such as the canary, modify their songs during adulthood. Nevertheless, the neural molecular mechanisms underlying open-ended vocal learning are not fully understood. We investigated the singing-driven expression of neural activity-dependent genes ( Arc , Egr1 , c-fos , Nr4a1 , Sik1 , Dusp6 , and Gadd45β ) in the canary to examine a potential relationship between the gene expression level and the degree of seasonal vocal plasticity at different ages. The expression of these genes was differently regulated throughout the critical period of vocal learning in the zebra finch, a closed-ended song learner. In the canary, the neural activity-dependent genes were induced by singing in the song nuclei throughout the year. However, in the vocal motor nucleus, the robust nucleus of the arcopallium (RA), all genes were regulated with a higher induction rate by singing in the fall than in the spring. The singing-driven expression of these genes showed a similar induction rate in the fall between the first year juvenile and the second year adult canaries, suggesting a seasonal, not age-dependent, regulation of the neural activity-dependent genes. By measuring seasonal vocal plasticity and singing-driven gene expression, we found that in RA, the induction intensity of the neural activity-dependent genes was correlated with the state of vocal plasticity. These results demonstrate a correlation between vocal plasticity and the singing-driven expression of neural activity-dependent genes in RA through song development, regardless of whether a songbird species possesses an open- or closed-ended vocal learning capacity.
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A major challenge for studies assessing drivers of phenotypic divergence is the statistical comparison of taxa with unique, often unknown, evolutionary histories, and for which there are no clear expected trait values. Because many traits are fundamentally constrained by energy availability, we suggest that trait values predicted by scaling theories such as the metabolic theory of ecology (MTE) can provide baseline expectations. Here, we introduce a metabolic scaling‐based approach to test theory involving the direction and magnitude of ecological and sexual selection, using vocal frequency as an example target of selection. First, we demonstrate that MTE predicts the relationship between the natural log of body size and natural log of vocal frequency across 795 bird species, controlling for phylogeny. Family‐wide deviations in slope and intercepts from MTE estimates reveal taxa with potentially important differences in physiology or natural history. Further, species‐level frequency deviations from MTE expectations are predicted by factors related to ecological and sexual selection and, in some cases, provide evidence that differs from current understanding of the direction of selection and identity of ecological selective agents. For example, our approach lends additional support to the findings from many cross‐habitat studies that suggest that dense vegetation selects for lower frequency signals. However, our analysis also suggests that birds in non‐forested environments vocalize at frequencies higher than expected based on MTE, prompting intriguing questions about the selective forces in non‐forest environments that may act on vocal frequency. Additionally, vocal frequency deviates more strongly from MTE expectations among species with smaller repertoires and those with low levels of sexual dichromatism, complicating the use of these common sexual selection surrogates. Broad application of our metabolic scaling approach might provide an important complementary approach to understanding how selection shapes phenotypic evolution by offering a common baseline across studies and taxa and providing the basis to explore evolutionary trade‐offs within and among multicomponent and multimodal traits.
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Context Anthropogenic noise is relatively new to natural soundscapes and may have adverse effects on acoustically active species. In birds, adverse effects include changes in vocalization patterns. Helicopters and songbirds are ubiquitous in protected natural areas but the effect of helicopter noise on songbirds has never been assessed. Objectives Our objective was to determine if helicopter noise affects temporal characteristics of songbird vocalizations within protected natural areas. Methods We collected soundscape recordings in three protected areas with varying levels of helicopter tour activity, including one with the second highest air tour activity in the United States. We examined songbird response to helicopter noise at the species level by measuring changes in vocalization time, and at the community level by employing the Bioacoustic Index, an acoustic measure of biological sound. Results We found a strong association between increasing helicopter noise and songbird vocalizations, indicating that some bird species use temporal shifts in vocalizations to mitigate masking effects from helicopter noise. The strength and direction of the response was species-specific, suggesting differences in resilience to helicopter noise between species. Furthermore, our results suggest that bird response to helicopter noise is strongest in areas with very loud and frequent helicopter traffic. Conclusions Our study is the first to examine and demonstrate impacts of helicopter noise on songbird vocalizations. Our results may serve as the foundation of an air tour management plan that considers reducing the number of helicopter overflights over protected natural areas and enforcing higher flight altitudes to decrease noise power levels.
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In tropical birds, survival is dependent on the ability to effectively communicate with others against a background of high ambient noise. The Acoustic Niche Hypothesis proposes that the deterrent selective force of signal masking has caused animals sharing a habitat to partition their calling behavior among the acoustic bandwidths available, so as to minimize interference between one another. Whether and why species share the so-called “acoustic space” remains a gap in our understanding of animal ecosystems. The aim of this study was to investigate differences between the acoustic structure of avian communities in two distinct habitats in the montane tropical forests of the Caparaó National Park in south-eastern Brazil, and to test whether the distribution of birdsong at each conformed to the ANH. Birdsong from nine hours of passive acoustic recordings at each study site was analyzed using principal component analyses. The results contradicted the ANH, revealing strikingly similar patterns of synchronized vocal behavior (WAleixo = 0.63, p < 0.0001, RA = 0.48; WSanta Marta = 0.66, p < 0.0001, RSM = 0.41). No correlation was evident between the acoustic and temporal partitioning behavior of songbirds (pA » 0.05, dfA = 55; pSM » 0.05; dfSM = 27). This study provides a novel comparative analysis of the acoustic dynamics in two separate and diverse avian communities and support for theories of synchronized vocal behavior in such groups.
Article
Numerical competence—the ability to estimate and process the number of objects and events—is important during antipredator strategies because it influences individual's survival chances. Animals can benefit from numerical competence during mobbing—when a prey moves toward and vocalizes at or harasses a predator. Mobbing responses of some species are related to the number of conspecific callers, and responses are stronger during playbacks simulating multiple callers. Here, we tested heterospecific individual vocal recognition (IVR) in combination with numerical competence in great tits (Parus major). Since previous work showed that great tits respond to mobbing calls of chaffinches (Fringilla coelebs), we predict that great tits showed a stronger response when two or four different individual chaffinches were played back versus only one individual by keeping the duty cycle (number of total calls/min) identical. Individuals were exposed to playbacks simulating calling by one, two or four heterospecific callers, or singing by one caller (control song). Great tits approached the speaker closer and produced more calls during the mobbing calls treatments than during the control treatment (song). However, in contrast to our prediction, great tits responded similarly to mobbing calls from several heterospecific callers as they did toward mobbing calls from one heterospecific caller. Maybe the great tits still are capable of determining the identity of the callers, but what might matter most for them in this very specific situation might be the mobbing intensity. We assume that the duty cycle itself has the stronger impact on the response.
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Nicotinic acetylcholine receptors (nAChRs) are ligand‐gated ion channels that mediate fast synaptic transmission and cell signaling, which contribute to learning, memory, and the execution of motor skills. Birdsong is a complex learned motor skill in songbirds. Although the existence of 15 nAChR subunits has been predicted in the avian genome, their expression patterns and potential contributions to song learning and production have not been comprehensively investigated. Here, we cloned all the 15 nAChR subunits (ChrnA1–10, B2–4, D, and G) from the zebra finch brain and investigated the mRNA expression patterns in the neural pathways responsible for the learning and production of birdsong during a critical period of song learning. Although there were no detectable hybridization signals for ChrnA1, A6, A9, and A10, the other 11 nAChR subunits were uniquely expressed in one or more major subdivisions in the song nuclei of the songbird brain. Of these 11 subunits, ChrnA3–5, A7, and B2 were differentially regulated in the song nuclei compared with the surrounding anatomically related regions. ChrnA5 was upregulated during the critical period of song learning in the lateral magnocellular nucleus of the anterior nidopallium. Furthermore, single‐cell RNA sequencing revealed ChrnA7 and B2 to be the major subunits expressed in neurons of the vocal motor nuclei HVC and robust nucleus of the arcopallium, indicating the potential existence of ChrnA7‐homomeric and ChrnB2‐heteromeric nAChRs in limited cell populations. These results suggest that relatively limited types of nAChR subunits provide functional contributions to song learning and production in songbirds. The expression of nicotinic acetylcholine receptors (ChrnA1–10, B2–4, D, and G) in the zebra finch brain showing unique differential expressions in subdivisions of the forebrain and the song nuclei. The white color represents mRNA signal.
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Zusammenfassung Musik hat eng mit Erotik und Sexualität zu tun, von Liebesspielen in der Oper über die Sexualsymbolik im Kunst- und Volkslied bis hin zur sexuell stimulierenden Musik im privaten und gewerblichen Bereich. Auf der anderen Seite steht Sexualverhalten eng mit dem endokrinen System im Zusammenhang. Eine Verbindung zwischen Musik und Hormonen liegt daher nahe, was allerdings in der Forschung bislang weitgehend ignoriert wurde. Der vorliegende Beitrag versucht durch seinen Fokus auf den Zusammenhang von Musik mit Hormonen, die im Sexualbereich eine Rolle spielen, eine (mögliche) Brücke zu schlagen. Dabei kommen konkret Testosteron, Östrogen, Oxytocin, Endorphine und Prolaktin zur Sprache. Sollte sich tatsächlich ein engerer neuroendokrinologischer Zusammenhang zwischen Musik und Sexualverhalten – was noch Forschungsdesiderat ist – herausstellen, so liegen Auswirkungen auf die Sexualsoziologie und Sexualtherapie nahe. Im Kontext mit dem vorliegenden Beitrag bezieht sich das wesentlich auch auf interkulturelle Aspekte und die Altchinesischen Sexualtherapie. Schlüsselwörter Musik, sexuelle Erregung, Endokrinologie, Oxytocin, Sexualtherapie Abstract Music, erotic feelings, and sexuality go hand in hand, as witnessed by love scenes in operas, sex symbols in songs, and sexually arousing music in private an commercial areas. On the other hand, sexual behaviour is closely interconnected with the endocrine system. Hence there are good reasons to consider hormones the missing link between both domains. Given that until today this aspect has been widely ignored by science, this article tries to explore the relation between music and selected hormones that modulate sexual behaviour and/or play a crucial role for sex-associated processes: testosterone, oestrogen, oxytocin, endorphins, and prolactin. If it turns out that neuro-endocrine processes modulate the still heuristic connection between music and sexual behaviour, findings will probably have a strong impact on the sociology of sexuality and sex therapy. Research referring to these topics, however, is still lacking. In this context, the present article also highlights cross-cultural issues and takes Ancient Chinese Sex Therapy into consideration. Keywords Music, sexual arousal, endocrinology, oxytocin, sexual therapy
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The discourse of posthumanism is made up of a group of approaches to cultural theory and philosophy that attempt to supersede perceived limitations of the humanisms of the twentieth-century. In the essay that follows, I will try to outline these approaches as they have taken shape over the last thirty years or so. I will suggest that their move beyond humanism points toward something implausible or even impossible: a thought that appears at a horizon beyond the human but is nevertheless our thought. Such a thought, posited as a goal of posthumanist projects, will only be approached asymptotically, converged on but never touched. Music offers us a means to track this convergence-music conceived widely enough to assert its own special position, which defines an aspect of human exceptionalism at the same time as it links human and nonhuman experience. Posthumanist lineages Like the "postmodernism" that anticipated it by several decades, "posthumanism" is a label that insists on qualification and apology. In what sense is "post-" meant, since it is not intended to signal merely a temporal succession beyond Enlightenment humanism and its twentieth-century outgrowths? Alternative terms have been suggested. Richard Grusin (2015) offers "nonhuman," a choice that can evade teleologies raised by post-. But its nominative form, nonhumanism, signals a cancelation of humanism or an antihumanism, which is not Grusin's intent; so a more specific denomination is required to name the recent gathering of momentum among theories of materiality, objects, technics, and so forth: the "nonhuman turn." Others address antihumanism head-on, embracing a term that has its own longer history connected to anti-Enlightenment and atheist thought. For Rosi Braidotti (2013:23), however, this move remains bound to Foucault's "death of Man" in The Order of Things (a move that, half a century later, can seem a weak gesture in that otherwise extraordinary book); the effort to dismantle the post-Enlightenment European subject now appears to be parochial and partial, indicating only one of several varieties of posthumanism. I have suggested "parahumanism," an alternative that avoids questions of temporality in favor of an extension beside and around the human (Tomlinson 2013,
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Данное пособие содержит изложение современных методов и возможностей по измерению и анализу акустических параметров звуков млекопитающих и птиц, а также принципов их записи в природных и лабораторных условиях. Пособие составлено в виде сборника задач, все задачи снабжены подробными руководствами и комментариями, что помогает студентам разобраться в актуальных проблемах биоакустических исследований на конкретных примерах и в ходе самостоятельной работы. Последовательность приведенных задач отражает практическую часть современной программы курса «Биоакустика позвоночных», проводимого коллективом авторов на кафедре зоологии позвоночных, биологического факультета МГУ имени М.В. Ломоносова.
Article
It is known that bird vocalizations and music share acoustic similarities. Unsurprisingly, bird sounds inspired a number of music composers. In music, complexity plays an important role in auditory attractiveness. Would sound complexity also be important to explain the attractiveness of bird vocalizations to humans? In our study, we experimentally assessed the preference for vocalizations according to their level of complexity, indicated by objective measurements. Further, given that men and women enjoy music similarly, we verified whether the taste for the sound of birds differs between the sexes. The study was conducted on 114 adults living in a rural district in the northeast of Brazil. The results showed a significant and linear preference for sounds, with the most complex ones being preferred. Moreover, both men and women were attracted to the songs of these animals. For the first time, the importance of complexity in humans’ appreciation for bird vocalizations has been objectively demonstrated. Our results stress the relationship between bird vocalizations and music for people. In addition to its theoretical nature, this study might be useful to predict, based on the sound complexity, which birds would be subject to a higher risk of capture, information that would help in reducing the loss of biodiversity. Moreover, giving the apparently universal aspect of bird song attraction to humans, it would be advisable in terms of conservation efforts to elect singing birds as flagship species. We hope that our research will serve as a motivation for further efforts in this area, as it clearly brings important insights into ethnozoology and other interdisciplinary fields.
Article
How vocal communication signals are represented in the cortex is a major challenge for behavioral neuroscience. Beyond a descriptive code, it is relevant to unveil the dynamical mechanism responsible for the neural representation of auditory stimuli. In this work, we report evidence of synchronous neural activity in nucleus HVC, a telencephalic area of canaries (Serinus canaria), in response to auditory playback of the bird’s own song. The rhythmic features of canary song allowed us to show that this large-scale synchronization was locked to defined features of the behavior. We recorded neural activity in a brain region where sensorimotor integration occurs, showing the presence of well-defined oscillations in the local field potentials, which are locked to song rhythm. We also show a correspondence between local field potentials, multi-unit activity and single unit activity within the same brain region. Overall, our results show that the rhythmic features of the vocal behavior are represented in a telencephalic region of canaries.
Article
Birdsong has been the subject of broad research from a variety of sub-disciplines and has taught us much about the evolution, function, and mechanisms driving animal communication and cognition. Typically, birdsong refers to the specialized vocalizations produced by oscines. Historically, much of the research on birdsong was conducted in north temperate regions (specifically in Europe and North America) leading to multiple biases. Due to these historic biases these vocalizations are generally considered to be highly sexually dimorphic, heavily shaped by sexual selection and essential for courtship and territoriality. Song is also typically defined as a learned trait shaped by cultural evolution. Together, this framework focuses research specifically on males, particularly during the north temperate breeding season - reflecting and thereby reinforcing this framework. The physiological underpinnings of song often emphasize the role of the hypothalamic-pituitary-gonadal axis (associated with breeding changes) and the song control system (underlying vocal learning). Over the years there has been great debate over which features of song are essential to the definition of birdsong, which features apply broadly to contexts outside males in the north temperate region, and over the importance of having a definition at all. Importantly, the definitions we use can both guide and limit the progress of research. Here, we describe the history of these definitions, and how these definitions have directed and restricted research to focus on male song in sexually selected contexts. Additionally, we highlight the gaps in our scientific knowledge, especially with respect to the function and physiological mechanisms underlying song in females and in winter, as well as in non-seasonally breeding species. Furthermore, we highlight the problems with using complexity and learning as dichotomous variables to categorize songs and calls. Across species, no one characteristic of song - sexual dimorphism, seasonality, complexity, sexual selection, learning - consistently delineates song from other songbird vocal communication. We provide recommendations for next steps to build an inclusive information framework that will allow researchers to explore nuances in animal communication and promote comparative research. Specifically, we recommend that researchers should operationalize the axis of variation most relevant to their study/species by identifying their specific question and the variable(s) of focus (e.g. seasonality). Researchers should also identify the axis (axes) of variation (e.g. degree of control by testosterone) most relevant to their study and use language consistent with the question and axis (axes) of variation (e.g. control by testosterone in the seasonal vocal production of birds).
Chapter
The introductory part of the chapter will display its whole purpose and topic. First of all, this section of the book aims to clarify the situation of both humanities and behavioural sciences after the discovery of animal thought and cultures. In other words, after the fundamental theoretical assumptions of these two scientific traditions were empirically refuted: the idea of man as the only thinking and cultural animal and other animals as mechanically explainable entities. From this the need for a critical and self-critical re-foundation of both humanities and behavioural sciences arises. A process which is in fact already underway but is still not reflecting enough on the level of theoretical elaboration and on the practical level of a reform of scientific training and research. This need for a new organization of university and post-university education, transversal to the bipartition between human and life sciences, and of meta-disciplinary forms of organization of the basic and applied research, on which the chapter aims to focus, is in various respects close to the goal of a radical self-reform of humanities proposed in Martinelli’s Manifesto of Numanities (Martinelli 2016). In this specific case, the pivot or pillar of this “revolution” of humanities is identifiable in the attempt to reorganize the humanistic field as Interspecific Cultural Studies. That is, as a meta-disciplinary area able to assume a post-anthropocentric approach towards its topics and collaborate, each sector starting from its own specificity, on an enterprise that we are attempting in our age for the first time: to insert the study of past and present human cultures into the broader context of a comparative study of all animal cultures, existing and existed. This enterprise would imply, as its indissoluble condition, the commitment to protect the survival of these animal cultures and of the natural environments in which they have evolved. The following section presents, in extreme synthesis, the state of the art of cultural ethology. The third section introduces, in an equally concise way, the emerging etho-centric approach to the explanation of evolutionary processes in contrast to the geno-centric one, recognizing not genes, but explorative and cognitive behaviours, experiences and cultural traditions as the main driving forces of animal evolution. The fourth section illustrates the basic characteristics of the meta-disciplinary area indicated in the chapter as Interspecific Cultural Studies (ICS) and their close affinities with the program of Numanities. The fifth section focuses, within the ICS framework, on a particular project and object of research: the study of the cases of Interspecific Cultural Convergences (ICC). These are cases in which a technique, an invention, a discovery, an expressive form or use have been independently developed not only by different populations of the same species, but also by societies and traditions of different animal species. The last part illustrates one of the best-known ICC cases: singing. A widespread expressive form in all human cultures and in primates genetically and phylogenetically quite distant from us such as Hylobatidae, Tarsius, Indri and Callicebus yet not among our sister species (chimpanzee, bonobo, gorilla). An expressive form developed by animal species as diverse and from a genetic, phylogenetic, morphological and ecological point of view as different as birds, mice and whales. The diffusion of singing in so different clades and environments obviously cannot be explained as a case of homology (similar characteristic inherited by common ancestor), because the ancestors common to birds and mammals did not sing, just as as those common to insects and birds did not have wings. It is instead the result of mutually independent, but in some aspects similar, evolutionary processes and social or ecological selective pressures. It can be adequately understood only by identifying and comparing the biological and social functions that this kind of expression plays, and the forms it has assumed, in all these animal communities, just as is commonly done by comparing human singing traditions and performances. In the ICS perspective, this approach can be extended to the study of all aspects of animal cultures and of all cases of ICC found.
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The extent of artificial night light and anthropogenic noise (i.e., “light” and “noise”) impacts is global and has the capacity to threaten species across diverse ecosystems. Existing research involving impacts of light or noise has primarily focused on noise or light alone and single species; however, these stimuli often co-occur and little is known about how co-exposure influences wildlife and if and why species may vary in their responses. Here, we had three aims: (1) to investigate species-specific responses to light, noise, and the interaction between the two using a spatially explicit approach to model changes in abundance of 140 prevalent bird species across North America, (2) to investigate responses to the interaction between light exposure and night length, and (3) to identify functional traits and habitat affiliations that explain variation in species-specific responses to these sensory stimuli with phylogenetically informed models. We found species that responded to noise exposure generally decreased in abundance, and the additional presence of light interacted synergistically with noise to exacerbate its negative effects. Moreover, the interaction revealed negative emergent responses for several species that only reacted when light and noise co-occurred. Additionally, an interaction between light and night length revealed 47 species increased in abundance with light exposure during longer nights. In addition to modifying behavior with optimal temperature and potential foraging opportunities, birds might be attracted to light, yet suffer inadvertent physiological consequences. The trait that most strongly related to avian response to light and noise was habitat affiliation. Specifically, species that occupy closed habitat were less tolerant of both sensory stressors compared to those that occupy open habitat. Further quantifying the contexts and intrinsic traits that explain how species respond to noise and light will be fundamental to understanding the ecological consequences of a world that is ever louder and brighter.
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Predictability is a relational, historically and culturally shaped concept. A phenomenon can be defined as predictable in relation to the available knowl- edge, instruments and methods, as well as the epistemic horizons in which its explanation is located (E. Fox Keller 2002). From this point of view, the last hundred years in the field of comparative study of animal behaviours and minds have led to radical changes in our epistemic horizon by extending our understanding of what we have to consider predictable or unpredictable in animal behaviours. Indeed, this historical phase has seen the discovery of entire classes of phenomena related to the expression of animal thought, languages, societies and cultures, which in the preceding decades would have been considered impossible within relevant scientific areas as anthropology, comparative psychology, theoretical and moral philosophy, linguistic and cul- tural studies. For instance, new sound analysis technologies developed over the last decades have allowed a decoding of bird songs that, pushing the limits of our sensory and cognitive channels, allowed us to appreciate its syntactic complexity and the richness of its intraspecific differentiations (cultural tra- ditions), radically modifying our views. In the last ten years, the analysis of the cerebral structures of birds has also demonstrated the presence of areas for processing and decoding acoustic communication similar to those found in our central nervous system. The brain of parrots, corvides and sparrows has been shown to have a higher neuronal density than that of mammals, including primates. Higher is also the percentage of neurons that are part of the brain areas destined to the so-called “superior functions” as the bark in mammals and the Pallium in birds. A research directed by Clifton W. Rags- dale, of the University of Chicago, has recently confirmed a close affinity between the mammal neocortex and the birds’ DVR, or ventricular backbone (J. Dugas-Ford, J.J. Rowell, C.W. Ragsdale 2012). In the last fifty years, the use of microphones suitable for recording in the deep sea, and the com- puterized analysis of sounds, made us begin to understand the complexity of whale songs, or the amazing analogies of the dolphins’ whistling with human names. In the same span of time, progress in the techniques of brain analysis has shown that the cetacean’s paralimbic system makes possible a very rapid integration of perceptions and a richness of information which is considered superior to the human one, and that cetacean such as humpback whales and dolphins have brains with even more cortical convolutions than humans (R. D. Fields 2008). These developments open up new perspectives, making it necessary to overcome, both in scientific training and in research, classical dichotomies such as nature/culture, Natural Sciences/Humanities. They integrate the horizon of the foreseeable, including the expectation of a gradual extension of the class of organisms that we should recognize as “cultural animals”, as well as of the phenomena to which this chapter is devoted: the cases of Cul- tural Convergent Evolution between different species.
Article
Research on avian vocalisations has traditionally focused on male song produced by oscine passerines. However, accumulating evidence indicates that complex vocalisations can readily evolve outside the traditional contexts of mate attraction and territory defence by male birds, and yet the previous bias towards male song has shaped – and continues to shape – our understanding of avian communication as a whole. Accordingly, in this review we seek to address this imbalance by synthesising studies on female vocalisations from across signalling contexts throughout the Aves, and discuss the implications of recent empirical advances for our understanding of vocalisations in both sexes. This review reveals great structural and functional diversity among female vocalisations and highlights the important roles that vocalisations can play in mediating female‐specific behaviours. However, fundamental gaps remain. While there are now several case studies that identify the function of female vocalisations, few quantify the associated fitness benefits. Additionally, very little is known about the role of vocal learning in the development of female vocalisations. Thus, there remains a pressing need to examine the function and development of all forms of vocalisations in female birds. In the light of what we now know about the functions and mechanisms of female vocalisations, we suggest that conventional male‐biased definitions of songs and calls are inadequate for furthering our understanding of avian vocal communication more generally. Therefore, we propose two simple alternatives, both emancipated from the sex of the singer. The first distinguishes song from calls functionally as a sexually selected vocal signal, whilst the second distinguishes them mechanistically in terms of their underlying neurological processes. It is clear that more investigations are needed into the ultimate and proximate causes of female vocalisations; however, these are essential if we are to develop a holistic epistemology of avian vocal communication in both sexes, across ecological contexts and taxonomic divides.
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