Thesis (M.Sc.). / Written for the Dept. of Natural Resource Sciences, Macdonald College. Title from title page of PDF (viewed 2008/07/24). Includes bibliographical references.

Cette thèse est une contribution expérimentale à l’étude des résonances aéroacoustiques des jets sous-détendus : le Screech. Diverses méthodes expérimentales sont utilisées à ces fins, telles que la mesure de pression acoustique, la strioscopie et Vélocimétrie par Image des Particules, et associées à des techniques classiques de post-traitement comme les décompositions en mode de Fourier et aux valeurs propres. Ces Techniques permettent d’évaluer les effets d’épaisseur de la lèvre de la buse sur l’écoulement, et fournissent des informations sur les différences de comportement d’un même jet montrant des modes oscillatoires différents. Enfin, on entreprend d’étudier la présence de divers mécanismes de fermeture de la boucle de résonance pour divers modes de screech. La présence d’ondes intrinsèques du jet, se propageant vers l’aval pour les modes axisymétrique (A2) et hélicoïdal (C) suggèrent que ces ondes puissent jouer un rôle dans la résonance. La signature de ces ondes n’est en revanche pas attestée pour les modes battants (B). Ces résultats semblent donc indiquer que plusieurs mécanismes de rétroaction différents puissent être à l’oeuvre dans la résonance du jet sous-détendus. / This work provides an experimental contribution to the study of the Screech phenomenon. Various experimental techniques such as microphones array, Schlieren and Particle Image Velocimetry (PIV) together with advanced post-processing techniques like azimuthal Fourier decomposition and Proper Orthogonal Decomposition (POD) are employed. These techniques enable the evaluation of the lip thickness effects on the jets generated by two different round nozzles. The differences on the flow aerodynamics and acoustics are discussed. Then, we carry out experiments to analyse the effects of the different dominant Screech modes (B and C) on the flow characteristics. No noticeable differences are found in the mean fields. However, the fluctuation fields shows the contrary: B mode has larger fluctuation. In the last part, we investigate the Screech closure mechanism. The signature of upstream jet waves is revealed in the axisymmetric (A2) and helical (C) mode. However, the mode B does not present evidence of this instability in the flow, indicating that its closure mechanism may be bonded to another kind of waves. The conclusion from the results is that the Screech phenomenon seems be driven by different closure mechanisms.

This study examined the exposure of the Eastern Screech-owl (Otus asio) to contaminants in apple orchards of southern Quebec. Using a worstcase scenario approach, secondary exposure to three organophosphorus insecticides, (phosmet, azinphosmethyl and phosalone), two anticoagulant rodenticides, (chlorophacinone and diphacinone), and residues of previously applied organochlorines, particularly DDT and metabolites, was assessed. Exposure to PCBs and trace metals was also considered. Small mammal species preyed upon by Screech-owls were captured in orchards for residue analysis on a continual basis for persistent compounds or after insecticide and rodenticide applications. Beginning in the winter of 2000, 98 nest boxes were constructed and installed in woods inhabited by Screech-owls, adjacent to orchards. These boxes were then repeatedly inspected for pellets and prey remains. Estimated exposure of Screech-owls 0-60 hr post-application was 0.641 mg/kg for phosmet and azinphosmethyl and 0.401 mg/kg for phosalone. Exposure to phosmet at this level may warrant concern. The acute poison zinc phosphide is now the primary means of small mammal control in the study area and the possibility of exposure to anticoagulant rodenticides is diminishing. Observed DDE residues were most elevated in the short-tailed shrew (Blarina brevicauda) and ranged from <1.00 to 26.29 ug/g (wet wt) in whole-body pools. A Screech-owl egg found in a nest box between two orchards may have been thinned by as much as 19.8%, of concern because thinning maintained at 15.0 - 20.0% has been linked to population decline. Only background levels of PCBs and trace metals were detected. Finally, over 950 Screech-owl case files were also obtained from one Canadian and seven United States wildlife rehabilitation facilities and analyzed for evidence that pesticide exposure was an underlying or contributing cause of admissions.

No description available.

L’effet du vol d’avancement sur le bruit de choc de jets supersoniques sous-détendus est étudié de manière expérimentale. La structure de tels jets est d’abord explorée, avec et sans vol simulé. L’analyse employée allie des visualisations strioscopiques à des mesures quantitatives de pression statique et de vitesse, par vélocimétrie laser Doppler et vélocimétrie par images de particules. L’accent est mis sur l’étude de l’écoulement moyen et des propriétés de la turbulence dans la couche de mélange. L’effet du vol sur la composante tonale du bruit de choc, le screech, est ensuite examiné. A l’aide d’une antenne azimutale de microphones placée dans le champ proche acoustique, une analyse fine des modes du screech est notamment proposée. Par ailleurs, plusieurs effets de cette composante de bruit sur la dynamique du jet sont mis en évidence, en particulier l’oscillation des chocs ; on montre que cette oscillation est intimement liée au mode du screech. De manière à étudier spécifiquement la composante large bande du bruit de choc, diverses techniques de suppression du screech sont ensuite explorées.L’utilisation d’une tuyère crénelée s’est révélée satisfaisante pour l’éliminer de manière non-intrusive et a permis de déduire son influence sur le bruit de choc large bande. Enfin, l’effet du vol sur cette dernière composante est déterminé par l’étude de l’évolution de sa fréquence centrale, de son amplitude et de sa forme spectrale en situation de vol simulé. Une explication des tendances observées est alors proposée à la lumière des résultats aérodynamiques obtenus. / The flight effects on the shock-associated noise components of underexpanded supersonic jets are experimentally studied. To begin with, the jet structure is investigated, with and without simulated flight. To that end, Schlieren visualizations are combined with quantitative measurements of static pressure and velocity, by laser Doppler velocimetry and particle image velocimetry. The investigation focuses on the mean flow and on the properties of the mixing layer turbulence. Then, the effects of flight on the tonal component of shock-associated noise, the so-called screech, are studied. By means of a near field, azimuthal microphone antenna, a detailed analysis of its modal behaviour is proposed. Furthermore, several effects of screech on the jet dynamics are highlighted, like the shock oscillations. It is shown that these oscillations are closely connected to the screech mode. In order to study specifically the broadband component of shock-associated noise, several screech suppression techniques are considered. It is found that a notched nozzle is successful in non-intrusively suppressing it. This device is then used to deduce the screech influence on the broadband shock-associated noise.Finally, some effects of flight on the latter component are pinpointed through the study of the evolutionof its amplitude, peak frequency and spectral shape under flight conditions. The observed tendencies are explained in light of the aerodynamic results obtained.

No description available.

O cerrado é a maior, mais rica e provavelmente a mais ameaçada savana tropical do mundo. No entanto, grande parte de sua área foi ocupada por empreendimentos de agropecuária, nos quais não foram respeitados princípios básicos de conservação, sendo que cada grupo ou táxon reage de forma diferente a mudanças ambientais desse tipo. As aves de rapina, como os Falconiformes e os Strigiformes, são especialmente prejudicadas, pois são considerados predadores de topo de muitas teias alimentares. Porém, para saber como essas aves são afetadas pelas mudanças ambientais causadas pela ação do homem é necessário entender quais fatores são relevantes na \"escolha\" do ambiente de determinada espécie e assim compreender a razão de uma possível seletividade de hábitat. Sendo assim, o presente estudo observou características ecológicas de duas espécies de corujas comuns e bem distribuídas no Brasil, Megascops choliba e Athene cunicularia. Dentre os objetivos estão analisar a metodologia de estudo dessas aves de rapina, com possíveis efeitos na detecção de contatos e verificar o uso de hábitat, em diferentes fisionomias de cerrado, por parte das duas espécies de corujas. O estudo foi realizado na região da Estação Ecológica de Itirapina, no interior do estado de São Paulo. Para contatar as corujas foram realizados experimentos de playback em pontos de amostragem distribuídos em quatro fisionomias (neste estudo consideradas habitats) de cerrado. A atividade vocal de M. choliba variou conforme a temperatura e a umidade relativa. Esta espécie respondeu mais ao playback em condições de temperatura e umidade relativa altas. Athene cunicularia mostrou variar sua atividade vocal conforme a fase da lua e a intensidade do vento. Indivíduos desta espécie respondem mais intensamente ao playback em noites de lua cheia e menos em noites com ventos mais fortes. As duas espécies de corujas se distribuem diferentemente entre as fisionomias de cerrado. Athene cunicularia distribui-se distintamente entre fisionomias fechadas e abertas (Hk-w = 9,976; p = 0,0188), utilizando mais frequentemente as os campos limpo e sujo. Megascops choliba também se distribui diferentemente entre as fisionomias de cerrado (Hk-w = 10,88; p = 2 0,0137), utilizando preferencialmente o campo cerrado e o cerrado s.s.. Segundo os modelos tidos como os melhores, pela seleção de modelos feita através do AIC (Aikaike\'s Information Criterion), a variável com maior poder explicativo é o número de arbóreas para as duas espécies. Megascops choliba e A. cunicularia se segregam ecologicamente, havendo partição divergente de recursos espaciais, devido a seus requisitos para nidificação e forrageamento. Ocorre sobreposição intermediária no uso do habitat entre ambas espécies (O = 0,466). Já quanto a amplitude de nicho espacial (uso de habitat) M. choliba foi generalista (Bst = 0,753) e A. cunicularia intermediária (Bst = 0,453). Sendo assim, estas espécies divergem na seleção de habitat, se distribuindo diferentemente entre as fisionomias de cerrado de acordo com o número de arbóreas. Este estudo sugere, ainda, a importância de se levar em consideração as variáveis climáticas em estudos com o uso de vocalizações de aves de rapina noturnas, servindo também de subsídio para pesquisas futuras sobre censo dessas aves. / The Cerrado biome is the largest, richest and perhaps the most threatened tropical savannah of the world. However, most part of its natural areas has been transformed on agrosystems and pastures where basic principles of conservation weren\'t respected. Each biological group or taxa are affected on different ways by this change. Birds of prey are particularly affected because of its position in trophic webs, as they are top predators. To understand how these birds are affected by change caused by human land use, it is necessary to understand which factors are important for habitat selection, and then understand the species-habitat relationship. Thus, we observed ecological aspects of two widespread and common owls on Brazil: Tropical Screech-Owls (Megascops choliba) and Burrowing Owl (Athene cunicularia). The main objectives of this study included an analysis of methodological aspects of studying these owls species through playback and observe their habitat use. The study was conducted in the Estação Ecológica de Itirapina, State of São Paulo, Brazil. For doing it, we used playback experiments to detect these owls on four different cerrado physiognomies Vocal activities of Tropical Screech-owls were more detected in conditions of higher temperature and humidity. On the other hand, the Athene cunicularia answered more to playback in lower wind speed conditions and/or at full moon nights. The Burrowing Owl explored more frequently open physiognomies of cerrado, as campo limpo and campo sujo (Hk-w = 9.976; p = 0.0188). Conversely, Megascops choliba is more often found on campo cerrado, avoiding campo limpo (Hk-w = 10.88; p = 0.0137). According to Aikaike\'s Information Criterion (AIC) selection model, the most important variable to explain the distribution of both species in cerrado is the number of trees. There was ecological segregation between Megascops choliba and A. cunicularia. The spatial niche was intermediarily segregated (Pianka´s niche overlap measure O = 0.466), according their different needs for nesting and foraging. Additionally, these owls displayed broader (M. choliba Bst = 0.753) or intermediate (A. cunicularia Bst = 0.453) spatial niche breadths. On this sense, these owls have different needs on habitat selection, and their different distributions in cerrado were related more intrinsically to the number of trees present on each physiognomy, which is related to their nesting and foraging requirements. Aditionally, this study suggests, the importance to consider the influence of weather conditions on broadcast survey techniques for nocturnal raptors, which may be considered in further studies on census of these birds.

No description available.

O cerrado é a maior, mais rica e provavelmente a mais ameaçada savana tropical do mundo. No entanto, grande parte de sua área foi ocupada por empreendimentos de agropecuária, nos quais não foram respeitados princípios básicos de conservação, sendo que cada grupo ou táxon reage de forma diferente a mudanças ambientais desse tipo. As aves de rapina, como os Falconiformes e os Strigiformes, são especialmente prejudicadas, pois são considerados predadores de topo de muitas teias alimentares. Porém, para saber como essas aves são afetadas pelas mudanças ambientais causadas pela ação do homem é necessário entender quais fatores são relevantes na \"escolha\" do ambiente de determinada espécie e assim compreender a razão de uma possível seletividade de hábitat. Sendo assim, o presente estudo observou características ecológicas de duas espécies de corujas comuns e bem distribuídas no Brasil, Megascops choliba e Athene cunicularia. Dentre os objetivos estão analisar a metodologia de estudo dessas aves de rapina, com possíveis efeitos na detecção de contatos e verificar o uso de hábitat, em diferentes fisionomias de cerrado, por parte das duas espécies de corujas. O estudo foi realizado na região da Estação Ecológica de Itirapina, no interior do estado de São Paulo. Para contatar as corujas foram realizados experimentos de playback em pontos de amostragem distribuídos em quatro fisionomias (neste estudo consideradas habitats) de cerrado. A atividade vocal de M. choliba variou conforme a temperatura e a umidade relativa. Esta espécie respondeu mais ao playback em condições de temperatura e umidade relativa altas. Athene cunicularia mostrou variar sua atividade vocal conforme a fase da lua e a intensidade do vento. Indivíduos desta espécie respondem mais intensamente ao playback em noites de lua cheia e menos em noites com ventos mais fortes. As duas espécies de corujas se distribuem diferentemente entre as fisionomias de cerrado. Athene cunicularia distribui-se distintamente entre fisionomias fechadas e abertas (Hk-w = 9,976; p = 0,0188), utilizando mais frequentemente as os campos limpo e sujo. Megascops choliba também se distribui diferentemente entre as fisionomias de cerrado (Hk-w = 10,88; p = 2 0,0137), utilizando preferencialmente o campo cerrado e o cerrado s.s.. Segundo os modelos tidos como os melhores, pela seleção de modelos feita através do AIC (Aikaike\'s Information Criterion), a variável com maior poder explicativo é o número de arbóreas para as duas espécies. Megascops choliba e A. cunicularia se segregam ecologicamente, havendo partição divergente de recursos espaciais, devido a seus requisitos para nidificação e forrageamento. Ocorre sobreposição intermediária no uso do habitat entre ambas espécies (O = 0,466). Já quanto a amplitude de nicho espacial (uso de habitat) M. choliba foi generalista (Bst = 0,753) e A. cunicularia intermediária (Bst = 0,453). Sendo assim, estas espécies divergem na seleção de habitat, se distribuindo diferentemente entre as fisionomias de cerrado de acordo com o número de arbóreas. Este estudo sugere, ainda, a importância de se levar em consideração as variáveis climáticas em estudos com o uso de vocalizações de aves de rapina noturnas, servindo também de subsídio para pesquisas futuras sobre censo dessas aves. / The Cerrado biome is the largest, richest and perhaps the most threatened tropical savannah of the world. However, most part of its natural areas has been transformed on agrosystems and pastures where basic principles of conservation weren\'t respected. Each biological group or taxa are affected on different ways by this change. Birds of prey are particularly affected because of its position in trophic webs, as they are top predators. To understand how these birds are affected by change caused by human land use, it is necessary to understand which factors are important for habitat selection, and then understand the species-habitat relationship. Thus, we observed ecological aspects of two widespread and common owls on Brazil: Tropical Screech-Owls (Megascops choliba) and Burrowing Owl (Athene cunicularia). The main objectives of this study included an analysis of methodological aspects of studying these owls species through playback and observe their habitat use. The study was conducted in the Estação Ecológica de Itirapina, State of São Paulo, Brazil. For doing it, we used playback experiments to detect these owls on four different cerrado physiognomies Vocal activities of Tropical Screech-owls were more detected in conditions of higher temperature and humidity. On the other hand, the Athene cunicularia answered more to playback in lower wind speed conditions and/or at full moon nights. The Burrowing Owl explored more frequently open physiognomies of cerrado, as campo limpo and campo sujo (Hk-w = 9.976; p = 0.0188). Conversely, Megascops choliba is more often found on campo cerrado, avoiding campo limpo (Hk-w = 10.88; p = 0.0137). According to Aikaike\'s Information Criterion (AIC) selection model, the most important variable to explain the distribution of both species in cerrado is the number of trees. There was ecological segregation between Megascops choliba and A. cunicularia. The spatial niche was intermediarily segregated (Pianka´s niche overlap measure O = 0.466), according their different needs for nesting and foraging. Additionally, these owls displayed broader (M. choliba Bst = 0.753) or intermediate (A. cunicularia Bst = 0.453) spatial niche breadths. On this sense, these owls have different needs on habitat selection, and their different distributions in cerrado were related more intrinsically to the number of trees present on each physiognomy, which is related to their nesting and foraging requirements. Aditionally, this study suggests, the importance to consider the influence of weather conditions on broadcast survey techniques for nocturnal raptors, which may be considered in further studies on census of these birds.

No description available.