Thesis (M.A.) -- University of Tennessee, Knoxville, 2006. / Title from title page screen (viewed on Sept. 20, 2006). Thesis advisor: Todd M. Freeberg. Vita. Includes bibliographical references.

De nombreuses études portant sur les dialectes ont ouvert de nouvelles perspectives sur l’origine, le maintien et la fonction des dialectes chez les oscines. Trois hypothèses ont été formulées : le modèle historique (les dialectes résulteraient d’effets secondaires de l’apprentissage vocal), le modèle de spécialisation raciale (les dialectes résulteraient de populations génétiquement distinctes) et le modèle d’adaptation sociale (les dialectes résulteraient d’apprentissages à fonction sociale). Les caciques cul-jaune (Cacicus cela) ont été un modèle pionnier pour la mise en évidence de dialectes sociaux. Paradoxalement, chez l’espèce voisine des caciques cul-rouge (Cacicus haemorrhous), les dialectes sont indiqués comme étant absents. Le but de cette étude est de vérifier l’existence de dialectes chez les C. cela, de rechercher leur présence chez les C. haemorrrhous, d’étudier leur distribution spatiale et leur stabilité temporelle, et de tester expérimentalement (chez C. cela) leur perception par les membres de la colonie. L’intégralité de l’étude a été réalisée en Guyane Française sur des colonies de nidification. Les paramètres acoustiques temporels et de fréquence des chants courts produits par les mâles de chaque espèce ont été mesurés au cours de plusieurs années. Des expériences ont été menées, où des chants de différents dialectes ont été diffusés dans les colonies. Nous avons trouvé un chant court similaire à celui de C. cela chez C. haemorrhous. Nous avons confirmé la présence de dialectes de colonies proches chez C. cela et démontré leur présence pour la première fois chez C. haemorrhous. Les dialectes des deux espèces présentent une variation temporelle rapide, avec des dialectes différents chaque année au même endroit (différence plus marquée chez les C. cela). Les C. cela discriminent les dialectes de leur propre colonie des dialectes d'origine lointaine. Ils répondent notamment à ces derniers en produisant la première note de leur chant court. Ces résultats favorisent l’hypothèse d’adaptation sociale pour les dialectes chez ces deux espèces de Cacicus. / Numerous studies of dialects opened new perspectives on the origin, sustained presence and function of dialects in oscine birds. Three hypotheses have been proposed: the historical model (dialects would be by-products of vocal learning), the racial specialization model (dialects would be due to genetic differences between populations) and the social adaptation model (dialects would result from socially adaptive learning processes). Yellow-rumped caciques (Cacicus cela) have been a pioneer model for evidencing social dialects. Paradoxically, dialects have been indicated as absent in the closely related species red-rumped caciques (Cacicus haemorrhous). This study aims to verify the existence of dialects in C. cela, seek after the presence of dialects in C. haemorrrhous, study their spatial distribution and temporal stability, and test experimentally (in C. cela) their differential perception by colony members. The whole study was performed in French Guyana at nesting colonies. We measured timing and frequency acoustic parameters of short songs produced by males of both species during several years. We conducted experiments at colonies where we played back songs from different dialects. We found a colonial “short song” similar to that of C. cela in C. haemorrhous. We confirmed the presence of neighboring colony dialects in C. cela and we demonstrated their presence for the first time in C. haemorrhous. Dialects in both species show a fast temporal variation, with different dialects every year at the same place (difference more pronounced in C. cela). C. cela birds discriminate the dialects of their own colony from those of far distant origin. They notably answer the latter by voicing the first note of their short song. These results are in favor of the hypothesis of social adaptation for dialects in these two Cacicus species.

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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.

[Truncated abstract] The identification of individual animals based on acoustic parameters is a non-invasive method of identifying individuals with considerable advantages over physical marking procedures. One requirement for an effective and practical method of acoustic individual identification is that it is call-independent, i.e. determining identity does not require a comparison of the same call or song type. This means that an individuals identity over time can be determined regardless of any changes to its vocal repertoire, and different individuals can be compared regardless of whether they share calls. Although several methods of acoustic identification currently exist, for example discriminant function analysis or spectrographic cross-correlation, none are call-independent. Call-independent identification has been developed for human speaker recognition, and this thesis aimed to: 1) determine if call-independent identification was possible in birds, using similar methods to those used for human speaker recognition, 2) examine the impact of noise in a recording on the identification accuracy and determine methods of removing the noise and increasing accuracy, 3) provide a comparison of features and classifiers to determine the best method of call-independent identification in birds, and 4) determine the practical limitations of call-independent identification in birds, with respect to increasing population size, changing vocal characteristics over time, using different call categories, and using the method in an open population. ... For classification, Gaussian mixture models and probabilistic neural networks resulted in higher accuracy, and were simpler to use, than multilayer perceptrons. Using the best methods of feature extraction and classification resulted in 86-95.5% identification accuracy for two passerine species, with all individuals correctly identified. A study of the limitations of the technique, in terms of population size, the category of call used, accuracy over time, and the effects of having an open population, found that acoustic identification using perceptual linear prediction and probabilistic neural networks can be used to successfully identify individuals in a population of at least 40 individuals, can be used successfully on call categories other than song, and can be used in open populations in which a new recording may belong to a previously unknown individual. However, identity was only able to be determined with accuracy for less than three months, limiting the current technique to short-term field studies. This thesis demonstrates the application of speaker recognition technology to enable call-independent identification in birds. Call-independence is a pre-requisite for the successful application of acoustic individual identification in many species, especially passerines, but has so far received little attention in the scientific literature. This thesis demonstrates that call-independent identification is possible in birds, as well as testing and finding methods to overcome the practical limitations of the methods, enabling their future use in biological studies, particularly for the conservation of threatened species.

Hypothesized functions of complex song in birds include a role in mate attraction and territory defense and, through regional dialects, in genetic substructuring of populations and speciation. The necessary first step in testing such functions is a detailed characterization of song organization and variability. This is provided for the Northern House Wren (Troglodytes aedon), a species noted for complex song, but lacking detailed descriptions. The species was studied at two sites in Alberta with a sample of 15,000 songs from 15 males. Males sang in long bouts, each song composed of multiple syllable types and repeated many times before switching. The population repertoire of 27 syllables was almost entirely shared, but used to construct novel repertoires of up to 200 different song types for individual males without evidence of a ceiling. Additional flexibility and constraints in song construction are discussed in view of the above noted functions of song complexity. / x, 111 leaves : ill., maps ; 29 cm

The Cerulean Warbler (Dendroica cerulea), a once common summer inhabitant and breeder in southern Indiana, has declined at both local and continental population levels. Effects of specific silvicultural practices on the distribution and abundance of the Cerulean Warbler is unknown. During the summers of 2005 & 2006, Cerulean Warblers were surveyed within the Morgan-Monroe and Yellowwood state forests, as well as the Hoosier National Forest in southern Indiana. Three forest types were surveyed; unharvested reference sites were compared with single tree selection treatments and treatments where a combination of group and single tree selection was used. Mean bird abundance was estimated from bird surveys to determine if a correlation exists between silvicultural regimes and Cerulean Warbler abundance. Cerulean Warblers were located in all treatment types, with no significant differences in abundance between or among treatment types examined. These results suggest that uneven-age management practices, such as single tree and group selection harvesting, provide suitable breeding habitat for Cerulean Warblers.Knowledge of Cerulean Warbler (Dendroica cerulea) male pairing status based on song rates and frequencies, as well as familiarity with non-song vocalizations could be an effective management tool when studying this species. Cerulean Warblers were recorded throughout the breeding season, and 18 song variables were measured and compared between paired and unpaired males using Logistic Regression. Unpaired males had higher song rates and higher minimum frequencies than paired male counterparts. Female and fledgling call notes were also recorded and quantitatively analyzed. These analyses offer further understanding of intraspecific call functions of this species. / Department of Biology

This work provides an initial characterization of song sharing among males in the Northern House Wren (Troglodytes aedon parkmanii). A sample of 21 different males was studied at two different locations across two breeding seasons in southern Alberta, Canada. In total, 35,067 songs were analyzed to assess patterns of song sharing among males within and between study sites and in returning males between years. Virtually all syllable types (n=27) were shared among males. However, they were used to create very large repertoires of mostly unique song types. Absolute levels of song sharing among males was low but song sharing was higher among neighbouring males and decreased with increasing distance between males and across study sites. These patterns are discussed as they relate to important issues in the process of song learning, in the functions of large song repertoires in mate attraction and territory defense, and in the potential formation of dialects in this species. / xi, 102 leaves ; 29 cm