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.

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.

The marine birds comprising the order Procellariiformes are an ancient and diverse assemblage. A large proportion are both nocturnal and burrow-nesting at their breeding colonies, where in sharp contrast to their behaviour at sea, they are highly vociferous. Virtually nothing is known regarding the adaptive features of this process. Various aspects of vocal behaviour have therefore been investigated from 1981 to 1983 for seven species at breeding stations in both the boreal and sub-tropical North Atlantic Ocean. In addition, the problem of how these birds return to their correct burrows at night has been considered. A detailed study was conducted on the Manx Shearwater Puffinus puffinus. Various approaches showed that immatures contribute most to the calling heard. Males establish and defend burrows, but both sexes partake in aerial calling. Calling at ground level serves both sexual and territorial functions, whereas aerial calling is probably mainly concerned with sexual advertisement. Some males are more silent in flight than others. These probably represent birds as yet without burrows, perhaps the youngest age classes. Flighting activity probably expedites the acquisition of burrows and mates in these birds which are awkward on land, and aerial calling probably improves signalling efficiency in attracting mates. Six other species (Bulweria bulwerii, Calonectris diomedea, Puffinus assimilis, Hydrobates pelagicus, Oceanodroma castro, Pelagodroma marina) were studied. As with Puffinus puffinus, sexual differences in voice exist for all except Bulweria and Pelagodroma, which also lack aerial calls. Thus a functional link exists between flight calls and their sexual divergence. Selection probably favours such divergence in species where males leave burrows to display in flight; the sexual identity of those species whose males do not is unambiguous as they remain in burrows and call. The calls of Puffinus puffinus and Hydrobates pelagicus were compared at local and regional levels. Divergence exists between but not within islands. Vocal drift in Puffinus puffinus is also apparent after several years. The calls of the nocturnal Procellariiformes are reviewed and discussed in relation to their systematics. The potential use of calls in petrel systematics is also evaluated and shown to be useful. Observations on Puffinus puffinus showed that olfactory and auditory cues are not used for burrow homing. Experiments also confirmed this, and point to sufficient visual development in this species, although other senses may be emphasised in different ecological situations.

No description available.

Vocal learning is one of the most distinctive characteristics of the modern human species. Through the intricate interaction between vocal motor and auditory systems during early sensitive periods, humans spontaneously master the ability to speak and decode speech. Because vocal learning is so rare in vertebrates, songbirds (Oscines) are the primary model organisms used in studies of acoustic communication and vocal learning. The acquisition of songs in birds and speech in humans (learning of complex sounds with syntactic structures) exhibit similar developmental trajectories. Research on song learning has focused primarily on vocal production with limited emphasis on the role of auditory perception. While auditory tuning and sensorimotor feedback are indispensable for successful vocal learning and communication, how auditory tuning emerges at different levels of the neural processing hierarchy and how sensorimotor integration occurs in the brain during vocal learning is not fully understood. The neurobiology research described here thus focuses on auditory tuning and sensorimotor integration in vocal learning songbirds using multiple experimental approaches. In the first chapter, I describe peripheral auditory tuning in several songbird species. Using operant conditioning, I trained individual birds to report audible tones and assessed hearing thresholds over the 0.5 to 10 kHz frequency range. I also examined the relationship between song spectral energy and hearing by analyzing song frequency-power spectra and audiograms across species. I found that across songbird species, regardless of age, rearing condition, and sex, hearing range was similar: 0.5 to 8 kHz. Notably, the vocal energy in courtship song matches each species auditory sensitivity, indicating the coevolution of sensory and vocal motor systems. In the second chapter, I describe neuronal tuning in the auditory cortex (AC) of female songbirds. While male songbirds exhibit experience-dependent neuronal tuning in AC, the nature of AC tuning in females that do not sing has not been studied. I used in vivo acute electrophysiological recordings to examine neural responses to tones, ripple stimuli and songs. I compared neuronal firing patterns in female AC between different species groups and rearing conditions. My results suggest that higher-order auditory processing in female songbirds is conserved across species and that early song experience affects some aspects of tuning in the AC of females, suggesting that females exhibit experience-dependent changes in auditory tuning across development. In the final chapter, I examine a potential sensorimotor integration site, the caudal striatum (CSt), and its role in vocal learning. Auditory neurons in CSt suggest that the region may integrate auditory inputs and vocal motor commands to modulate sensorimotor learning. To study the effects of CSt lesions on song learning, I produced excitotoxic lesions in CSt across developmental stages. To label brain regions that project to or receive input from CSt, I injected anterograde or retrograde tracers into CSt. I also characterized the auditory tuning properties of CSt through electrophysiological recording. I found that CSt receives both dopaminergic and auditory projections but is not necessary for successful song learning. Electrophysiological data also show that auditory tuning properties of neurons in CSt are highly similar to neurons in other AC subregions, suggesting that CSt may be a sub-region of AC.

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

Made available in DSpace on 2015-08-20T17:10:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-03. Added 1 bitstream(s) on 2015-08-20T17:26:02Z : No. of bitstreams: 1 000840982.pdf: 1252667 bytes, checksum: 7069bb98ea402999ba81d7d978408194 (MD5) / 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 ...

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.