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Rufous-legged Owl ( Strix rufipes ) and Austral Pygmy Owl ( Glaucidium nanum ) stand use in a gradient of disrupted and old growth Andean temperate forests, Chile

2012; Taylor & Francis; Volume: 47; Issue: 1 Linguagem: Inglês

10.1080/01650521.2012.665632

1744-5140

José Tomás Ibarra, Nicolás Galvéz, Alessandro Gimona, Tomás A. Altamirano, Isabel Rojas, Alison J. Hester, Jerry Laker, Cristián Bonacic,

Ecology and Vegetation Dynamics Studies

Abstract We studied how human induced structural changes in forests affect stand use of the Rufous-legged Owl (forest-specialist) and the Austral Pygmy Owl (forest-facultative), in a gradient from lowland disrupted forests to protected Andean forests in Chile. We also tested if the calls of one species influenced the calling behaviour of the other. We detected a total of 34 Rufous-legged Owls and 21 Austral Pygmy Owls during the four seasons. Rufous-legged Owls were found principally in old growth Araucaria-Nothofagus stands (32.4%), and Pygmy Owls in old growth evergreen stands (52.4%). For both species there was a seasonal effect on call response, with a drop in responses in autumn and winter. Our models suggested that Rufous-legged Owls inhabit a more specific range of habitat characteristics than Pygmy Owls. The former selected stands with tall trees, relatively low tree density, and high bamboo density. Pygmy Owls selected stands with tall trees and relatively high tree density. There was no evidence that either species influenced the calling behaviour of the other, suggesting no negative association between use of a territory by the two species. Our results emphasize the importance of structural components of old growth forests for both species, but also the relevance of stands surrounding protected areas. Estudiamos cómo los cambios estructurales en el bosque, inducidos por el ser humano, afectan el uso de hábitat del concón (especialista de bosque) y del chuncho (facultativo de bosque), en un gradiente desde bosques perturbados en zonas bajas hasta bosques andinos protegidos de Chile. También evaluamos si los llamados de una especie influencian el comportamiento de vocalización de la otra. Detectamos un total de 34 concones y 21 chunchos para las cuatro estaciones del año. Los concones fueron registrados principalmente en bosques antiguos de Araucaria-Nothofagus (32.4%), y los chunchos en bosques antiguos siempre-verdes (52.4%). Para ambas especies hubo una disminución de la actividad en otoño e invierno. Nuestros modelos sugirieron que el concón tiene requerimientos de hábitat más específicos que el chuncho. El concón seleccionó bosques con árboles altos y en baja densidad relativa, y una alta densidad de quila. Por su parte, el chuncho seleccionó bosques con árboles altos y en alta densidad relativa. No hubo evidencia de que los llamados de una especie afectaran las respuestas de la otra, sugiriendo que no existe una asociación negativa en el uso de un mismo territorio por ellas. Los resultados enfatizan la importancia de los elementos estructurales de los bosques antiguos para ambas especies pero, a su vez, la relevancia de los bosques periféricos a áreas protegidas. Keywords: Akaike's Information Criterionbird habitat useChileforest structural componentsinterspecific competitionowlstemperate forests Acknowledgments This study was funded by the Darwin Initiative (Project 15‐006) and the Chilean Ministry of the Environment (FPA Projects 9‐040‐09, 9‐078‐10 and 9‐I‐009‐12). It also received the support from the Cleveland Metroparks Zoo, Cleveland Zoological Society, the Rufford Small Grants for Nature Conservation and The Peregrine Fund. We thank Dr. Hernán Vargas, the Chilean Forest Service (CONAF), Lahuén Foundation, Guías Cañe, and Kawellucó Private Sanctuary. We sincerely thank D. Altamirano, A. Barreau, F. Hernández, O. Ohrens, R. Petitpas, C. Ríos, R. Sanhueza, and M. Venegas for invaluable help in the field. JTI, NG, TAA, and IR are supported by a grant from Comisión Nacional de Investigación Científica y Tecnológica (CONICYT). Three anonymous reviewers made valuable contributions on early versions of this manuscript. This article is a contribution to the Fauna Australis (PUC) Bird Conservation and Banding Programme in the Andean temperate forests of the Araucanía District.