Factores extrínsecos e intrínsecos que influyen en la dinámica temporal de las asociaciones de alimentación en aves marinas
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2016
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es
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Universidad Andrés Bello
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Licencia CC
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Para aumentar la eficiencia de forrajeo y contrarrestar los costos energéticos que la jerarquización del océano demanda, las aves marinas comúnmente observan la conducta de otras aves para encontrar a sus presas, mecanismo facilitador denominado "local enhancement". A través de este mecanismo se desencadena habitualmente la formación de asociaciones multi-específicas de alimentación (AMA). A pesar de la alta conspicuidad de las AMA, su multi-dimensionalidad ha dificultado dilucidar cuáles son las variables (extrínsecas e intrínsecas) de mayor importancia sobre su dinámica y estabilidad temporal. Entre julio de 2006 y septiembre de 2014 se hicieron conteos mensuales de aves marinas en la Bahía de Valparaíso. Esta zona se caracteriza por presentar una marcada estacionalidad en la disponibilidad de alimento y por presentar un alto flujo migratorio con aves proveniente de la Antártida, Australia/ Nueva Zelanda y América del Norte. El objetivo de esta tesis fue determinar la importancia de variables extrínsecas (i.e. disponibilidad de alimento; capítulo 1) e intrínsecas (i.e. identidad taxonómica, gremio de forrajeo, tiempo migratorio, origen migratorio y tamaño corporal; capítulo 2) sobre la dinámica temporal de las AMA. En el capítulo I se puso a prueba la hipótesis que los atributos de las AMA (i.e. frecuencia de ocurrencia, abundancia, composición) serían modulados extrínsecamente por la marcada estacionalidad en la disponibilidad de alimento del área de estudio. En el capítulo 2 se determinó la causalidad que tienen los rasgos intrínsecos (i.e. identidad taxonómica, gremio de forrajeo, tiempo migratorio, origen migratorio y tamaño corporal) de las especies sobre la estabilidad estacional de la composición de las AMA. Utilizando imágenes satelitales de la concentración de clorofila-a como proxy de la disponibilidad de alimento y modelos lineales generalizados (GLM. multiGLM) se demostró que la marcada estacionalidad en la productividad del área de estudio no tuvo una influencia significativa sobre los atributos de las AMA. Los resultados de esta tesis sugieren que la estabilidad estacional de la composición de las AMA responde jerárquicamente a factores inherentes a las especies; siendo los hábitos migratorios de las aves primeramente determinantes y en último término los rasgos intrínsecos de las especies. Utilizando análisis de redes y modelos nulos en el capítulo 2 se demostró que las asociaciones tienden a ocurrir entre especies más similares fenotípica y/o conductualmente, que lo esperado por azar. Durante las estaciones migratorias (otoño-primavera) y reproductiva (verano) las especies se asocian considerando su similitud conductual y/o fenotípica, sin preferencias a nivel de especies, mientras que durante la hibernación las AMA presentaron una fuerte estructuración con preferencias a nivel de especies, dentro de los grupos taxonómicos (Procellariiformes y Charadriiformes). En esta tesis se demuestra que independiente de la disponibilidad estacional de alimento, el "local enhancement" es un importante mecanismo facilitador para las aves marinas y que en último término esta modulado principalmente por los rasgos intrínsecos de las especies.
In order to enhance foraging efficiency and offset the energetic costs of the ocean's hierarchy, seabirds commonly observed the behavior of other birds to find their prey, facilitative mechanism known as local enhancement. As a result, this mechanism usually triggers the formation of multispecies feeding flocks (MSFFs). Despite the high conspicuity of MSFF, their multidimensionality has hindered to elucidate the most important variables in its dynamic and temporal stability. Between July 2006 and September 2014, we conducted monthly at-sea seabird counts at Valparaiso Bay. This area is characterized by a marked seasonality in food availability and by a high migratory flow with birds coming from Antarctica, Australia/Nueva Zeeland y Norte America. The aim of this thesis was to determine the importance of extrinsic (i.e. food availability; chapter 1) and intrinsic variables (i.e. taxonomic identity. foraging guild, migratory timing, migratory origin and body size; chapter 2) on the temporal dynamics of MSFF. In chapter 1 we hypothesized that MSFF attributes (i.e frequency of occurrence, abundance and composition) will be modified according to the seasonal availability of food. In chapter 2 we determine the causality of species intrinsic traits on the seasonal stability of species composition within MSFF. Using chlorophyll-a concentration as a proxy and generalized linear models (GLM, multiGLM). we demonstrate that the contrasting seasonality in food availability of the study area had no significant influence on MSFF attributes. The results of this thesis suggest that the seasonal stability in the composition of MSFF, hierarchically responds to factors inherent to the species; being the migratory habits of birds the primarily determinant and ultimately the species intrinsic traits. Using network analysis and null models in chapter 2 we demonstrate that associations typically occurs between more phenotypically or behaviorally similar species than expected by chance. During migratory (autumn and spring) and reproductive (summer) seasons species associates considering their behavioral and/or phenotypic similarity, but with no preferences at the species level, whereas during the hibernation MSFF presented strong structuration and preferences at the species level within taxonomic groups (Procellariiformes y Charadriiformes). This thesis demonstrates that independent of the seasonal food availability, local enhancement is an important facilitator mechanism for seabirds and that ultimately is modulated mainly by species intrinsic traits.
In order to enhance foraging efficiency and offset the energetic costs of the ocean's hierarchy, seabirds commonly observed the behavior of other birds to find their prey, facilitative mechanism known as local enhancement. As a result, this mechanism usually triggers the formation of multispecies feeding flocks (MSFFs). Despite the high conspicuity of MSFF, their multidimensionality has hindered to elucidate the most important variables in its dynamic and temporal stability. Between July 2006 and September 2014, we conducted monthly at-sea seabird counts at Valparaiso Bay. This area is characterized by a marked seasonality in food availability and by a high migratory flow with birds coming from Antarctica, Australia/Nueva Zeeland y Norte America. The aim of this thesis was to determine the importance of extrinsic (i.e. food availability; chapter 1) and intrinsic variables (i.e. taxonomic identity. foraging guild, migratory timing, migratory origin and body size; chapter 2) on the temporal dynamics of MSFF. In chapter 1 we hypothesized that MSFF attributes (i.e frequency of occurrence, abundance and composition) will be modified according to the seasonal availability of food. In chapter 2 we determine the causality of species intrinsic traits on the seasonal stability of species composition within MSFF. Using chlorophyll-a concentration as a proxy and generalized linear models (GLM, multiGLM). we demonstrate that the contrasting seasonality in food availability of the study area had no significant influence on MSFF attributes. The results of this thesis suggest that the seasonal stability in the composition of MSFF, hierarchically responds to factors inherent to the species; being the migratory habits of birds the primarily determinant and ultimately the species intrinsic traits. Using network analysis and null models in chapter 2 we demonstrate that associations typically occurs between more phenotypically or behaviorally similar species than expected by chance. During migratory (autumn and spring) and reproductive (summer) seasons species associates considering their behavioral and/or phenotypic similarity, but with no preferences at the species level, whereas during the hibernation MSFF presented strong structuration and preferences at the species level within taxonomic groups (Procellariiformes y Charadriiformes). This thesis demonstrates that independent of the seasonal food availability, local enhancement is an important facilitator mechanism for seabirds and that ultimately is modulated mainly by species intrinsic traits.
Notas
Tesis (Magíster en Biología Marina)
Palabras clave
Aves Marinas, Alimentación y Alimentos