Dissertations / Theses on the topic 'Bird vocalizations'

An undue focus on Temperate Zone oscines (songbirds or passerines) has led to a geographical bias in interpretation of song frmnction and evolution. This bias led initially to relatively simplistic theories of the ftmnction of bird song with vocalizations divided into 'songs' and 'calls'. Songs were complex, learned vocalizations, given by males in the breeding season, thnctioning in territory defence and mate attraction and stimulation. Calls, on the other hand, were simple innate vocalizations serving more immediate needs such as begging for food and raising an alarm. Female song, where it occurred, was considered an aberration. Further studies suggested that complex songs were associated with mate attraction functions while simpler songs were associated with territory defence. However it became apparent that the distinction between songs and calls was not nearly so clear-cut and the supposed connection between complexity and function in song was questioned. Moreover it was realised that female song could not be dismissed as a mere aberration. Another problem was the ftmnction of the dawn chorus, where research had failed to find a consistent, all-encompassing explanation. Since most studies had been done on Northern Hemisphere songbirds, it was becoming clear that the geographical focus needed to be broadened. The life histories of Northern Hemisphere TemperateZone songbirds are very different from those in many other regions. In contrast to the situation in this zone, maintenance of year-round territory, territory defence by both male and female, life-long social monogamy and extensive female vocalization are widespread in tropical, subtropical and Southern Hemisphere regions. Recently it has been suggested that more intensive studies of vocalizations in these regions might help clariQi some of these issues and consequently an endemic Australian passerine was chosen for the current study. The study focused on the vocalizationsof the grey butcherbird Cracticus torquatus Artamidae, which displays the life history features described above. The main study population was located in the Brisbane suburbs of Rainworth and Bardon. Additional data were gathered from other Brisbane suburbs and bushland sites within the city and at Lake Broadwater near Dalby, Queensland. Vocalizations were initially recorded electronically and analysed using Canary sound editing program. Vocalization data were supplemented using an aural recording method, which was independently checked for reliability. Behavioural data including posture during vocalizations and interactions with other birds were also gathered. Initial investigationsrevealed the existence of two main categories of vocalizations - those given by the family group during the day, all year round and those given at dawn by males during the breeding season. For the focal study populations, group vocalizations were studied throughout the year over several years, however the song given at dawn by males during the breeding season proved to be quite complex and three birds from three territories in the main study area were chosen as case studies. Recordings were made of the vocalizations of the three case study birds over three breeding seasons. Starting and fmishing times (with respect to civil twilight) were recorded in order to determine both changes in song bout duration and starting time throughout the breeding season. Additional birds from the same area, from the other Brisbane suburbs and from the bushland sites were studied to check the validity of conclusions drawn from the case studies. The results of the investigations revealed a vocalization structure that contrasted strongly with the simple picture of bird song drawn from study ofNorthernHemisphere Temperate Zone passerines. The vocalizations given during the day, often referred to as the 'song' of this species, were very different from the early dawn song given by the male during the breeding season. This latter appeared to be song sensu stricto according to the paradigms developed for Northern Hemisphere birds. The thytime vocalizations, however, fitted neither the classic definition of 'song' nor the classic definition of 'call'. This relatively long-term study revealed different starting time patterns and periodicity for thy vocalizations and male breeding season song. Day vocalizations commenced at a fairly constant time with respect to civil twilight throughoutthe year but breeding season song started progressively earlier from the beginning through to the middle of the season then progressively later till the end of the season. Relative finishing time of breeding song however remained constant so that the duration of breeding season song gradually increased then decreased paralleling the change in starting times. A consequence of the two distinct classes of vocalizations was that there were essentially two distinct 'dawn choruses'. One, consisting of group vocals, was sung all year round; the other was given by males singing 'breeding season' song. Since there was no reason the expect that a single function would necessarily be ascribed to both choruses, this raised the possibility that some of the confusion surrounding the ftinction and nature of the 'dawn chorus' originated from a failure to recognize the existence of two such choruses. Variation in time and space showed ifirther differences between the two vocalization classes. The breeding song of each male was distinctly different from that of his neighbours and there was a marked change in the repertoire of any individual from one year to the next. In marked contrast, daytime vocalization repertoires of neighbouring groups were virtually indistinguishable and changed little from year to year. These findings, together with information from recent literature, suggested that the two song classes had a different ontogeny, function and possibly evolution. It was proposed that territory declaration was the function of dawn singing by grey butcherbird family groups but that the function most consistent with adult male dawn song was attraction of females for extra-pair copulations. It was suggested that chorusing itself was to some extent an accidental by-product of the advantage to the individual or group of singing at dawn although a recently proposed function, the social dynamics function, could not be ruled out. Further differences from the Northern Hemisphere situation were detected in subsong. First, subsong was given by birds in their first year and also by adult males. The finding of subsong in adult males was not without precedent as it has been documented previously for a small number of passerines, especially those that change repertoire from year to year. Subsong in young (first year) birds, however, was unusual in that birds practised in small groups rather than in the complete isolation usually associated with subsong. Moreover they did not practise adult male song but instead practised group daytime vocalizations. It was suggested that it was important for birds to learn to sing in company for the important task of group territory defence. Further investigation of the literature and observations during the present study revealed similar vocalization classes and behaviours in other members of the Artamidae and other endemic Australasian taxa. These literature investigations also revealed that the possession two song vocalization classes was quite widespread although they tended to be restricted (but not exclusive) to males rather than found in males and females. These findings led to furtherresearch into the significanceofAustraliain the evolution of songbirds, the role of co-operative breeding in Australianpasserines, and finally to an hypothesis for a possible origin of male bird song. It is suggested that male song arose in a social environment where the male and female were in frequent vocal communication. If the tendency to seek extra-pair copulations (EPCs) and female choice had already been incorporated into the suite of passerine behaviours, it would be necessary to avoid the mate during such activities and the male would need to advertise with a signal distinct from group vocalizations. Early dawn, with poor light conditions, could be a favourable time for these activities. Thus it is proposed that the ancestral condition was with all group members singing most vocalisations, the intermediate situation was similar to that in the grey butcherbird and the 'advanced' condition was where female and other group member vocalizations (other than calls) have dropped out and only male song remains.

Le Quetzal Resplendissant Pharomachrus mocinno est une espèce d’oiseau tropical considérée fortement menacée par la perte de son habitat due aux activités humaines. Le Quetzal Resplendissant joue un rôle important de disperseur de graines et constitue le centre de la culture maya passée et présente. Les recherches sur cette espèce couvrent plusieurs aspects de son histoire naturelle et de sa biologie. Néanmoins, à ce jour, il n’y a aucune description détaillée du comportement et de l’écologie acoustiques de cette espèce, condition préalable à une conservation efficace de l'espèce. L’objectif de cette thèse a été d’étudier tout particulièrement le comportement et l’écologie acoustique de P. mocino dans la forêt nuageuse du Guatemala. Une analyse détaillée des vocalisations de P. mocinno, incluant des expériences de propagation de ses vocalisations dans son habitat, a permis d’identifier deux types de vocalisations destinés à la communication à longue distance et deux autres types de vocalisations destinés à la communication à courte distance. La quantification des différences dans les vocalisations territoriales des deux sous-espèces de Quetzals Resplendissants, P. m. mocinno (partie nord de l’Amérique centrale et sud du Mexique) et P. m. costaricensis (sud de l'Amérique centrale) a révélé de nettes différences entre les sous-espèces, ce qui conforterait l'hypothèse d’espèces distinctes. L'observation de l'espèce dans la canopée dense est difficile et la manipulation des individus est controversée en raison de sa grande importance culturelle. De fait, un système acoustique automatique a été mis au point pour suivre l’espèce de manière non invasive. Le système s'est avéré efficace et a produit des résultats révélant des profils de suivis acoustiques en partie dépendants de variables environnementales. Enfin, la communauté acoustique des oiseaux à laquelle P. mocinno appartient a été analysée afin d’évaluer les interactions interspécifiques de compétition. Les recherches développées ici devraient aider aux décisions de conservation futures concernant le Quetzal Resplendissant et son habitat, la forêt nuageuse. Cette recherche montre également que l'écoacoustique peut constituer une stratégie utile pour aborder les problèmes d'écologie et de conservation dans les zones tropicales
The Resplendent Quetzal Pharomachrus mocinno is a tropical bird considered in a high risk of danger. Degradation of its habitat caused by human activities is the principal menace. The Resplendent Quetzal is important as seed disperser and is the centre of the past and present Mayan culture. The available studies about the species have covered aspects of the natural history and biology. Nevertheless, the description of the acoustic behaviour and ecology, a prerequisite for the conservation of the species, was not available. The general aim of this PhD thesis was to investigate the acoustic behaviour and ecology of P. mocinno in the cloud forest of Guatemala. A detailed analysis of P. mocinno vocalizations, including propagation experiments of these vocalizations in its habitat, led to identify two vocalizations intended for long range, and two for short range communication. Quantification of acoustic parameters in territorial vocalizations of the two subspecies of the Resplendent Quetzal, P. m. mocinno (north part of Central America and Chiapas) and P. m. costaricensis (south part of Central America), revealed clear differences between the subspecies, that could support a species separation hypothesis. . The observation of the species in the dense canopy is difficult and manipulation of individuals is controversial due to its high cultural importance. Then, an automatic acoustic system was developed as a method to study the species in a non-invasive way. The system proved to be efficient and returned results that revealed acoustic patterns linked to environmental variables. Finally, the acoustic community of other bird species P. mocinno belongs to was analysed so that interspecific competition interactions could be assessed. The research here developed should help in future conservation decisions about the Resplendent Quetzal and its habitat, the cloud forest. This research also illustrates that ecoacoustics can be a valuable strategy to tackle ecology and conservation questions in tropical areas

The taxonomy of the taxa in the Prinia atrogularis-khasiana-superciliaris complex has changed several times in recent history. To this day, different world bird lists classify this complex as 1–3 species. These classifications are based mainly on morphological comparisons of museum specimens. No study has analysed the songs and genetics of this complex. This thesis focuses on the integrative taxonomy of this complex by analysing and comparing their song and mitochondrial cytochrome b (cytb) gene. Seventeen different variables from in total 172 individual songs were measured and analysed. A linear discriminant analysis showed a clear separation in song between atrogularis, khasiana and the superciliaris group (latter including the taxa superciliaris, erythropleura, klossi, dysancrita and waterstradti). The mitochondrial cytb phylogenetic tree produced using Bayesian inference suggested that atrogularis and khasiana split from superciliaris around 4.9 million years ago (mya), with atrogularis and khasiana splitting from each other around 3.4 mya. Based on the combined results of the song and cytb analysis I propose to recognise three species: Black-throated Prinia Prinia atrogularis, Rufous-crowned Prinia P. khasiana and Hill Prinia P. superciliaris. The study also showed some support for classifying klossi as a separate species, but acquisition of additional information is needed to verify this.

Vocalization behavior of captive loggerhead shrikes was studied at the Avian Science and Conservation Centre of McGill University. In the first stage, calls of two pairs kept in indoor cages were individually recorded not only to catalogue these calls spectrographically and quantitatively but also to use them in identifying the birds sexually. Males vocalized 21 call figures for 16.50% of the observation time and females, 8 call figures for 2.64% of the observation time. Males contiguously delivered 1 to 11 bouts with a mean of 7.25 min for a rate of 6.06 bouts/h; females delivered 1 to 9 bouts with a mean of 4.07 min for a rate of 1.27 bouts/h. Males not only vocalized at a higher rate and longer than females, but also demonstrated trill calls which the females did not do. In the second stage, five pairs were paired in large outdoor breeding pens. Their calls were recorded and current visual displays observed in an effort to understand calls related to breeding behaviors. Two new calls figures vocalized by males as well as 2 call figures by young shrikes were recorded. Each male demonstrated distinctive calls that differed from those of other males during nest-site selection, nest building and copulation, but similar calls during food offering, aggressive and alarm behavior. Despite the call differences, all males performed similar visual displays during the above activities. Conversely, breeding females gave no calls, other than harsh calls during food offering, food begging, aggressive and alarm behaviors.

Mestrado em Ecologia Aplicada
Ecological changes in the habitats, induced by climate change or the new paradigms of land use, have had enormous effects in the distribution of species, from the fragmentation of the populations to changes on the genome and/or their behavior. In the case of birds, these constraints may cause changes in vocal repertoires among isolated populations. It was recently confirmed that the two last populations of Red-billed Chough (Pyrrhocorax pyrrhocorax) resident in Portugal (populations of the Serra d'Aire e Candeeiros and Sagres) have an apparent gene-flow restriction, suggesting an isolation that is not explained only by the geographical distance that separates them. In fact, the species has a high dispersion capacity which can not itself justify this restriction of genes between these two populations. Being the species a corvid with a high cognitive capacity and gregarious species, the communication between individuals becomes a vital point to its survival. This work intends to investigate if the gene-flow restriction is due to a social segregation that can be reflected in the variations of the vocal repertoire between the two populations. The aim of this study was to describe and try to understand the main differences between the two populations, as well as possible variations among individuals of the same population (in this case, only in Serra d'Aire e Candeeiros). The results showed that the two studied populations have different repertoires, were described five call types from the population in the Serra d'Aire e Candeeiros and only four in the population of Sagres, thus not existing an evident common vocal repertoire between both populations. It was verified that among the populations the greatest differences are in the duration, maximum frequency and final frequency, where the population from Sagres has smaller durations and maximum frequencies and a higher final frequency than the population from Serra d'Aire e Candeeiros. In the case of the differences between individuals analysed at the intra-population level, these showed individual variations, namely peak frequency and ascending time. Overall, the results seem to corroborate the thesis that the genetic isolation of these populations can be attributed to communication and social barriers.
As mudanças no estado ecológico dos habitats, induzidas por alterações climáticas e/ou por novos paradigmas dos usos do solo, têm tido inúmeras consequências na distribuição das espécies, desde a fragmentação das populações, passando por mudanças no genoma e no seu comportamento. No caso das aves, estes constrangimentos poderão traduzir-se em mudanças nos repertórios vocais entre populações isoladas. Recentemente, confirmou-se que as duas últimas populações de Gralha de Bico Vermelho (Pyrrhocorax pyrrhocorax) residentes em Portugal (populações da Serra d’Aire e Candeeiros e de Sagres) apresentam uma aparente restrição de fluxo genético entre si, sugerindo um isolamento que não se explica apenas pela distância geográfica que as separa. De facto, a espécie apresenta uma elevada capacidade de dispersão o que não pode, só por si, justificar esta restrição de genes. Sendo a espécie um corvídeo com uma elevada capacidade cognitiva e gregária a comunicação entre indivíduos torna-se vital à sua sobrevivência. Este trabalho pretende investigar se a restrição do fluxo genético se deve a uma segregação social que pode refletir-se nas variações do repertório vocal entre as duas populações. Com este intuito, o presente estudo teve como objetivo descrever e tentar compreender quais as principais diferenças entre as duas populações, bem como possíveis variações entre indivíduos de uma mesma população (neste último caso apenas na Serra d’Aire e Candeeiros). Os resultados demonstraram que as duas populações estudadas exibiram repertórios diferentes, com a existência de cinco tipos de vocalizações para a população da Serra na Serra d’Aire e Candeeiros e apenas quatro na população de Sagres, não havendo uma partilha evidente de entre tipos de vocalização comuns a ambas as populações. Verificou-se que entre as populações as maiores diferenças estão na duração, frequência máxima e frequência final, sendo que na população de Sagres as vocalizações têm durações e frequências máximas menores e a frequência final maior que as da população de Serra d’Aire e Candeeiros. No caso das diferenças entre indivíduos analisados ao nível intra-populacional, estes mostraram variações individuais nomeadamente na frequência de pico e do tempo de ascensão. Globalmente, os resultados parecem corroborar a tese de que o isolamento genético destas populações pode ser imputável também a barreiras comunicacionais e sociais.

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Este trabalho teve como objetivo analisar e comparar as vocalizações entre indivíduos e subespécies de Thamnophilus doliatus de diferentes localizações da América Latina. Foram analisados 280 cantos de 140 indivíduos diferentes, e as variáveis levadas em consideração foram: número de notas, duração do trecho em sequência, taxa de notas por segundo, frequência de pico total do trecho, duração da nota terminal e frequência de pico da mesma. Os cantos também foram divididos em porções para se calcular a variação de velocidade e de tonalidade (frequência) ao longo dos trechos. As características do canto foram correlacionadas com dados geográficos como latitude, longitude e altitude a fim de se conferir se existe alguma padronização com a localização, e a amostra também foi agrupada em subespécies de acordo com suas localizações para comparações. As variáveis analisadas foram fortemente correlacionadas com a latitude, indicando que indivíduos de localização equatorial emitem cantos com mais notas, mais longos, mais rápidos e com uma nota terminal mais grave do que aqueles localizados ao sul da distribuição. As variáveis também foram correlacionadas com a longitude, incluindo também a frequência de pico. Foram identificadas sete subespécies de acordo com as localidades em que foram gravadas, porém apenas cinco foram utilizadas para comparações. Resultados mostraram uma separação das subespécies intermedius e radiatus pelas significativas diferenças no número de notas, duração do trecho, taxa de notas por segundo e frequência de pico. Também foram feitas comparações com a recém-separada espécie Thamnophilus capistratus, e só foram encontradas diferenças significativas na nota terminal e na variação de frequência ao longo do trecho. Devido às características do canto se mostrarem mais próximas entre diferentes espécies (T. doliatus e T. capistratus), que entre as subespécies de...
The aim of this study was to analyze and to compare vocalizations of individuals of the species Thamnophilus doliatus from different locations of Latin America. 280 loudsongs from 140 individuals were analyzed and the variables taken into account were the following: number of notes, duration of the sequenced patch, note rate (notes per second), overall peak frequency, duration of the terminal note, and peak frequency of the terminal note. The loudsongs were also divided into portions in order to measure the variation of note rate (speed) and pitch (frequency) along the patch. The loudsong characteristics were correlated with geographic factors such as latitude, longitude and altitude to check if there is any acoustic pattern with the location. Also, the sample was clustered into subspecies for comparisons. The analyzed variables were strongly correlated with latitude, where individuals from equatorial locations had loudsongs with more notes, longer in duration, faster in note rate and a terminal note lower in peak frequency. The variables also appeared to be significantly correlated with longitude, including as well the overall peak frequency. Seven subspecies were identified according to their locations, however, only five of them were used for comparisons. Results showed a separation of the intermedius and radiatus subspecies due to their significant divergence in number of notes, patch duration, note rate and peak frequency. Comparisons with the recently separated species Thamnophilus capistratus were also made and no significant variation were found in the number of notes and total duration, but there were differences in note rate, overall peak frequency, peak frequency and duration of the terminal note. Because song characteristics between the different species (T. doliatus and T. capistratus) presented to be more similar than among the subspecies of T. doliatus, raises the question of the existence of more than one species within ...

Orientador: Reginaldo José Donatelli
Banca: Manoel Dias Filho
Banca: Carolina Demetrio Ferreira
Resumo: Este trabalho teve como objetivo analisar e comparar as vocalizações entre indivíduos e subespécies de Thamnophilus doliatus de diferentes localizações da América Latina. Foram analisados 280 cantos de 140 indivíduos diferentes, e as variáveis levadas em consideração foram: número de notas, duração do trecho em sequência, taxa de notas por segundo, frequência de pico total do trecho, duração da nota terminal e frequência de pico da mesma. Os cantos também foram divididos em porções para se calcular a variação de velocidade e de tonalidade (frequência) ao longo dos trechos. As características do canto foram correlacionadas com dados geográficos como latitude, longitude e altitude a fim de se conferir se existe alguma padronização com a localização, e a amostra também foi agrupada em subespécies de acordo com suas localizações para comparações. As variáveis analisadas foram fortemente correlacionadas com a latitude, indicando que indivíduos de localização equatorial emitem cantos com mais notas, mais longos, mais rápidos e com uma nota terminal mais grave do que aqueles localizados ao sul da distribuição. As variáveis também foram correlacionadas com a longitude, incluindo também a frequência de pico. Foram identificadas sete subespécies de acordo com as localidades em que foram gravadas, porém apenas cinco foram utilizadas para comparações. Resultados mostraram uma separação das subespécies intermedius e radiatus pelas significativas diferenças no número de notas, duração do trecho, taxa de notas por segundo e frequência de pico. Também foram feitas comparações com a recém-separada espécie Thamnophilus capistratus, e só foram encontradas diferenças significativas na nota terminal e na variação de frequência ao longo do trecho. Devido às características do canto se mostrarem mais próximas entre diferentes espécies (T. doliatus e T. capistratus), que entre as subespécies de...
Abstract: The aim of this study was to analyze and to compare vocalizations of individuals of the species Thamnophilus doliatus from different locations of Latin America. 280 loudsongs from 140 individuals were analyzed and the variables taken into account were the following: number of notes, duration of the sequenced patch, note rate (notes per second), overall peak frequency, duration of the terminal note, and peak frequency of the terminal note. The loudsongs were also divided into portions in order to measure the variation of note rate (speed) and pitch (frequency) along the patch. The loudsong characteristics were correlated with geographic factors such as latitude, longitude and altitude to check if there is any acoustic pattern with the location. Also, the sample was clustered into subspecies for comparisons. The analyzed variables were strongly correlated with latitude, where individuals from equatorial locations had loudsongs with more notes, longer in duration, faster in note rate and a terminal note lower in peak frequency. The variables also appeared to be significantly correlated with longitude, including as well the overall peak frequency. Seven subspecies were identified according to their locations, however, only five of them were used for comparisons. Results showed a separation of the intermedius and radiatus subspecies due to their significant divergence in number of notes, patch duration, note rate and peak frequency. Comparisons with the recently separated species Thamnophilus capistratus were also made and no significant variation were found in the number of notes and total duration, but there were differences in note rate, overall peak frequency, peak frequency and duration of the terminal note. Because song characteristics between the different species (T. doliatus and T. capistratus) presented to be more similar than among the subspecies of T. doliatus, raises the question of the existence of more than one species within ...
Mestre

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Given the strong relationship between the birds and the environments where they live, this study aimed to characterize the temporal dynamics of molts, breeding, abundance and vocalizations of Pseusoseisura cristata, as well as the influence of climatic periods under these aspects. Data collection was monthly between June 2011 and May 2012. The Caatinga area studied is located in the municipality of São José do Egito, Pernambuco - Brazil. Nine mist nets were used to capture and record brood patch and molts. The sampling effort was equal to 3564 hours/net. The abundance was estimated through three "strip transects" and the temporal structure of vocalizations were recorded through sound contacts with unlimited radius. It was verified that the climatic periods influence the molts and breeding. Both occur during the rainy season, since they require a large supply of resources to meet the energy demands of the processes. The seasonality also exerts a subtle influence on the temporal structure of vocalizations, forming different patterns for the dry and rainy seasons. However, these patterns must be further linked to breeding the rainfall itself. The abundance in turn, was not altered as a function of climate, revealed that this species is better adapted to climatic variations of the environment.
Diante da forte relação entre as aves e os ambientes onde vivem, esta pesquisa objetivou caracterizar bioecologicamente a dinâmica temporal de mudas, reprodução, vocalizações e abundância de Pseusoseisura cristata, bem como a influência dos períodos climáticos sob estes aspectos. A coleta de dados foi mensal entre junho de 2011 e maio de 2012. A área de Caatinga estudada localiza-se no município de São José do Egito, Pernambuco - Brasil. Nove redes de neblina foram utilizadas para captura e registro de mudas e placas de incubação, sendo o esforço amostral igual a 3564 horas/rede. A abundância foi estimada através de três “strip transects” e a estrutura temporal de vocalizações foi registrada através de contatos sonoros com raio ilimitado. Pôde-se verificar que há influência dos períodos climáticos sobre as mudas e sobre a reprodução. Ambos ocorrem durante o período chuvoso, pois necessitam de uma grande oferta de recursos para suprir a demanda energética dos processos. A sazonalidade também exerce uma sutil influência sobre a estrutura temporal das vocalizações, formando padrões diferentes para os períodos seco e chuvoso. No entanto, estes padrões devem estar mais ligados à reprodução do que à pluviosidade propriamente dita. A abundância por sua vez, não foi alterada em função do clima, revelando que a espécie apresenta adaptabilidade às variações climáticas do ambiente.

Tese de Doutoramento em Biologia, especialidade de Ecologia, apresentada à Faculdade de Ciências e Tecnologia, Universidade de Coimbra
Estudámos a dinâmica evolutiva e aspectos selectivos das duas características sexuais secundárias mais proeminentes em passeriformes – canto e coloração – por meio de experimentação no serino (Serinus serinus) e de análises comparativas no género Serinus. A velocidade e frequência aguda das canções de serino são extremas quando comparadas com as restantes espécies do género, o que sugere evolução por selecção sexual. Em experiências comportamentais, fêmeas de serino manifestaram preferência por canções agudas; canções rápidas, pelo contrário, inibiram as respostas das fêmeas. Os machos de serino não discriminaram quanto à frequência das canções, mas foram inibidos por canções rápidas. Estes resultados sugerem pressões selectivas distintas: a evolução da frequência de canto é compatível com um processo de selecção inter-sexual, e a velocidade das canções parece ser um sinal agonístico, passível portanto de selecção intra-sexual. Documentamos um padrão de diversificação evolutiva intensa do canto no género Serinus, que se sobrepõe a constrangimentos vocais importantes. A evolução do canto neste género foi apenas parcialmente acompanhada por adaptação vocal às características das canções nas diferentes espécies. Tal deve-se, pelo menos em parte, ao facto de várias espécies evoluírem características de complexidade silábica em relação às quais detectámos custos de produção vocal fortes. Diferentes sintaxes de canto correlacionam-se com aspectos distintos de desempenho vocal, o que sugere formas de selecção indirecta sobre a sintaxe. A coloração apresenta um padrão de evolução intensa em ambos os sexos de Serinus spp., como é típico de características sexualmente seleccionadas. Mostramos que a coloração conspícua em fêmeas evoluiu sobretudo por constrangimento sexual, pelo que advertimos contra a inferência de causalidade evolutiva a partir do valor adaptativo presente de ornamentos femininos. Os principais eixos de complexidade do canto e elaboração da coloração estão fortemente correlacionados entre as espécies de Serinus, e tendem a variar com aspectos do habitat que indicam maior intensidade de selecção sexual, sugerindo que selecção sexual é o processo selectivo mais determinante na sua evolução.

Thesis (Ph.D.)--York University, 2004. Graduate Programme in Biology.
Typescript. Includes bibliographical references (leaves 109-136). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ99143

Alarm or warning vocalizations are produced by many animals when they detect a potential predator. However little is known about the information contained in these vocalizations. This study investigated the warning vocalisations of three passerine species, viz. the Buff-streaked Chat Oenanthe bifasciata, the Stonechat Saxicola torquata and the Bronze Mannikin Spermestes cucullatus. The study investigated whether the alarm calls for terrestrial predators differ in their acoustic structure from alarm calls emitted for aerial predators. Birds were exposed to latex terrestrial snakes and mounted aerial raptors, while changes in six acoustic parameters of alarm calls were measured. Bronze Mannikins were investigated for differences in intra-specific alarm calls between familiar and unfamiliar group members by capturing wild groups of mannikins and randomly mixing these to form assorted groups. Bronze Mannikins emitting warning calls were able to discriminate differences in predator size, and increased their calling rate and decreased the end frequency of the alarm call in response to larger predators. This may be the caller’s response to increased threat or variation in frequency may obscure cues to the caller’s whereabouts. Assorted group members were less aggressive to predator models than original members and panicked more during confrontations. Hence the unfamiliarity of the caller may have disrupted group cohesion. The alarm call acoustics of the social Buff-streaked Chats and the solitary Stonechat were compared to examine the effect of group-living on alarm behaviour. Snakes elicited louder calls from both the chat species than raptors. Louder and collectively more vocal social groups might be more successful in discouraging attacks than an asocial species. Variation in amplitude and call frequencies by the Stonechat provided some evidence that they are equally adapted to identifying predator type. Although Buff-streaked Chats increased their call rate in response to nearby predator models, Stonechats produced shorter calls in response to terrestrial predation particularly when the predators were in close proximity. Knowledge gained through direct encounters with predators or the ease with which raptors and snakes can gain access to nests may have played a part in discrimination of predator threat. Overall this study indicated strong correlations between some alarm acoustic parameters and predator size as well as the degree of threat.
Thesis (M.Sc.)-University of KwaZulu-Natal, 2008.

Mimicry of other species' alarm calls is common among birds, but its function is often unknown. Although anti-predator functions for mimetic alarm calls have been suggested, these are yet to be tested. In this thesis I formally evaluated claims of vocal mimicry in the brown thornbill (Acanthiza pusilla) and tested if mimetic vocalisations function in preventing nest predation. Both male and female thornbills are capable of mimicking a range of different vocalisations, including heterospecific contact calls, songs, and alarm calls. Mimetic vocalizations also varied greatly in acoustic structure: both high and low frequency vocalisations were mimicked. Despite the diversity in the types of vocalisations thornbills can mimic, they predominantly mimicked heterospecific alarm calls when captured in mist-nets. Although these mimetic alarm calls were not identical to their corresponding model species' alarm calls, they did retain acoustic features of model alarm calls that are important for provoking immediate alarm responses by receivers. Brown thornbills mimicked heterospecific alarm calls more often in circumstances of danger, and especially when callers or their offspring were in extreme danger. These mimetic alarm calls communicated honest information about flying and stationary predators, but inaccurate information (presence of an aerial predator) when callers or their offspring were under attack. These findings suggest that the thornbill's mimetic alarm calls play different functions in different circumstances of danger. In nest defence, thornbills mimic heterospecific mobbing alarm calls (alarm calls given by heterospecifics towards terrestrial predators) if a predator is near their nest and mimic aerial alarm calls (alarm calls given by heterospecifics towards aerial predators) if the nest is under attack. Mimicking mobbing alarm calls towards predators near the nest potentially hides the caller's identity and may reduce risk of alarm calls revealing the nest's location to the predator. Mimicking aerial alarm calls when the nest is under attack potentially fools the predator that it is in danger, causing distraction and providing young with an opportunity to escape. A playback experiment on the thornbill's primary nest predator, the pied currawong (Strepera graculina), supported the hypothesis that mimetic aerial alarm calls cause distraction and provide nestlings with an opportunity to escape when attacked. Currawongs responded with typical alarm responses and delayed feeding following either the thornbill's non-mimetic aerial alarm alone or a combination of non-mimetic and mimetic alarms. Including mimetic alarms with non-mimetic alarms prolonged currawong distraction.

Sound is used as a medium for communication by taxa as varied as insects, fish, amphibians, birds and mammals. In some birds like the suboscines, song is genetically encoded, whereas in parrots, hummingbirds and oscines, it is learnt. The diversity and plasticity of birdsong continues to generate interest amongst ornithologists, and many questions remain unresolved. For instance, why do some species sing hundreds of different songs while others use simple, stereotyped ones for the same purposes? Why do some birds learn not only their own species’ song, but also the songs of heterospecifics? There are several anecdotal reports of such vocal mimicry in wild birds, where a species imitates the song or call of heterospecifics in its natural habitat, but much has yet to be learnt about this intriguing phenomenon. There has been a recent surge of interest and research into avian vocal mimicry. Despite having several species of birds that are known to produce mimicry, there is a dearth of research on this field in India. The Greater Racket-tailed drongo’s loud song and ability to mimic other species of birds with great accuracy has drawn the attention of many birdwatchers, but other than a few phonetic descriptions, no study has focussed on their song. Therefore, this thesis focuses on the structure, contexts and functions of vocal mimicry in this species. In order to understand the functions of vocal mimicry in any species, we require certain fundamental data, which are often overlooked in many studies of bird song. Since this is the first study focusing on the racket-tailed drongo in India, I began with collecting natural history data on the ecology and breeding biology of the species. Then, I attempted to arrive at an objective and quantitative definition and classification of the racket-tailed drongo’s vocal repertoire, especially its mimicry. It is also essential to have information on the contexts in which this mimicry is used. Using a combination of focal animal sampling and sound recordings, I documented the contexts in which the racket-tailed drongo imitates other species in the wild. I also examined the diversity of the species that were mimicked across these contexts. Building on the data from these observations, I used playback experiments to test hypotheses for the functions of mimicry in multiple contexts. Results from these show that greater racket-tailed drongos use mimicry in a flexible manner according to the intended audience. Drongos use two different sets of mimicked calls with distinct syntax directed at conspecifics and heterospecifics respectively, the former in territorial song and the latter to attract members of mixed-species flocks. These results also imply that mimicry may be driven by both sexual and natural selection within the same species, and have implications for the definition of avian vocal mimicry, which remains highly debated.

Mice produce many ultrasonic vocalizations (USVs) in the 30 - 100 kHz range including pup isolation calls and adult male songs. These USVs are often used as behavioral readouts of internal states, to measure effects of social and pharmacological manipulations, and for behavioral phenotyping of mouse models for neuropsychiatric and neurodegenerative disorders; however, little is known about the biophysical and neurophysiological mechanisms of USV production in rodents. This lack of knowledge restricts the interpretation of data from vocalization-related experiments on mouse models of communication disorders and vocal medical conditions. Meanwhile, there has been increased interest in the social communication aspect of neural disorders such as autism, in addition to the common disorders involving motor control of the larynx: stroke, Parkinson's disease, laryngeal tremor, and spasmodic dysphonia. Therefore, it is timely and critical to begin assessing the neural substrate of vocal production in order to better understand the neuro-laryngeal deficits underlying communication problems.

Additionally, mouse models may generate new insight into the molecular basis of vocal learning. Traditionally, songbirds have been used as a model for speech learning in humans; however, the model is strongly limited by a lack of techniques for manipulating avian genetics. Accordingly, there has long been strong interest in finding a mammalian model for vocal learning studies. The characteristic features of accepted vocal learning species include programming of phonation by forebrain motor areas, a direct cortical projection to brainstem vocal motoneurons, and dependence on auditory feedback to develop and maintain vocalizations. Unfortunately, these features have not been observed in non-human primates or in birds that do not learn songs. Thus, in addition to elucidating vocal brain pathways it is also critical to determine the extent of any vocal learning capabilities present in the mouse USV system.

It is generally assumed that mice lack a forebrain system for vocal modification and that their USVs are innate; however, these basic assumptions have not been experimentally tested. I investigated the mouse song system to determine if male mouse song behavior and the supporting brain circuits resemble those of known vocal learning species. By visualizing activity-dependent immediate early gene expression as a marker of global activity patterns, I discovered that the song system includes motor cortex and striatal regions active during singing. Retrograde and anterograde tracing with pseudorabies virus and biodextran amines, respectively, revealed that the motor cortical region projects directly to the brainstem phonatory motor nucleus ambiguus. Chemical lesions in this region showed that it is not critical for producing innate templates of song syllables, but is required for producing more stereotyped acoustic features of syllables. To test for the basic components of adaptive learning I recorded the songs of mechanically and genetically deaf mice and found that male mice depend on auditory feedback to develop and maintain normal ultrasonic songs. Moreover, male mice that display natural strain specific song features may use auditory experience to copy the pitch of another strain when housed together and stimulated to compete sexually. I conclude that male mice have neuroanatomical and behavioral features thought to be unique to humans and song learning birds, suggesting that mice are capable of adaptive modification of the spectral features of their songs.

Dissertation

Relationship between animal signalization and environmental conditions, where these species are living, is one of crucial topics of ecology. Using two complementary statistical approaches (fourth-corner and RLQ analyzes) I investigated geographical variation in parameters of bird vocalization in South Africa (RSA) and Lesotho. Altogether, I used nine quantitative and five qualitative acoustic traits for 472 bird species and nine environmental variables which could significantly influence parameters of their vocalization. My results supported findings of previous studies about the important effect of body size on species-specific vocal characteristics. In passerines, analyzes corrected for body size showed that the number of elements and element types were increasing with variability of natural conditions and were highest in very arid and climatically unpredictable areas. Element and element type rate were positively associated with altitude. Minimal song frequency in passerines and frequency range of vocalization in other birds were negatively correlated with average temperature of warmest and coldest month of the year, respectively. Similarly, environmental variables significantly influenced distribution of several qualitative song traits in passerines. Passerines, where female song and...