Abstract

NANNI, A. Sofía; ORTIZ, Pablo E; JAYAT, J. Pablo  and  MARTIN, Eduardo. Variación estacional de la dieta de la Lechuza de Campanario (Tyto alba) en un ambiente perturbado del Chaco Seco argentino. Hornero [online]. 2012, vol.27, n.2, pp.149-157. ISSN 0073-3407.

Seasonal variation in the diet of the Common Barn-Owl (Tyto alba) in a disturbed environment of the Argentinean Dry Chaco We studied the diet of the Common Barn-Owl (Tyto alba) in the Dry Chaco of Santiago del Estero, Argentina. From 332 pellets collected between 2007 and 2009 we analyzed the seasonal variation in number and biomass of prey-items, diversity, and trophic niche width. We identified 1170 individuals belonging to 14 prey-items, corresponding to mammals (87%), birds (7%) and insects (6%). Cricetid rodents were the most frequent group (85%) with the highest biomass contribution (>75%), being Calomys spp. the most abundant item. During the dry season of the first year, the abundance of micromammals reached the highest values while birds and insects showed the opposite pattern. Diversity and trophic niche width showed their highest values during the wet season and niche overlap was lower between samples of different seasons. Seasonal variation in biomass was mostly due to a higher consumption of birds during the wet season of 2008. In the wet season of the second year the diet showed an anomalous behaviour, in some cases showing the opposite of the expected patterns, probably related to a pronounced decrease in rainfall. The results of this study allow us to confirm a generalist-opportunistic diet, with high consumption of micromammals during the dry season probably explained by their high population sizes. Environmental modifications could be explaining the extreme dominance of Calomys spp., as it has been documented in other regions of Argentina.

Keywords : Common Barn-Owl; Dry Chaco; Northwestern Argentina; Seasonal diet; Trophic niche.

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