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Diet and Trophic Characteristics of Great Horned Owls in Southwestern Idaho (Dieta y Caracteristicas Tróficas de Bubo virginianus En El Suroeste de Idaho)

Carl D. Marti and Michael N. Kochert
Journal of Field Ornithology
Vol. 67, No. 4 (Autumn, 1996), pp. 499-506
Published by: Wiley on behalf of Association of Field Ornithologists
Stable URL: http://www.jstor.org/stable/4514149
Page Count: 8
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Diet and Trophic Characteristics of Great Horned Owls in Southwestern Idaho (Dieta y Caracteristicas Tróficas de Bubo virginianus En El Suroeste de Idaho)
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Abstract

We studied the diet of Great Horned Owls (Bubo virginianus) in the Snake River Birds of Prey National Conservation Area in southwestern Idaho for 14 breeding seasons. The diet included 89.2% mammals by number and 91.2% by mass. Kangaroo rats (Dipodomys spp.) were the most common prey overall, but montane voles (Microtus montanus), Peromyscus spp., Great Basin pocket mice (Perognathus parvus) and Townsend's pocket gophers (Thomomys towsendii) were most common at some collection sites. Estimated mean mass of prey was 44.5 g (range 20.5-82.6 g at individual nests), and food-niche breadth (dietary diversity estimated by $1/\Sigma p_{{\rm i}}{}^{2}$) was 7.32 (range 1.55-6.85 at individual nests). Lower mean overlap in diet occurred between nests in the same year than between years at the same nest. Species of prey taken were significantly correlated with the general habitat types in which the nest was located. Diets of owls in areas of intensive agriculture overlapped little (42%) with those in rangeland habitats. /// Estudiamos la dieta de Bubo virginianus en el Area Nacional de Conservación para Aves de Rapiña de Snake River, en el suroeste de Idaho, durante 14 temporadas de reproducción. La dieta incluyó 89.2 mamíferos por número (91.2 por masa). La presa más comunmente ingerida fué Dipodomys, pero en algunos puntos de colección las especies Microtus montanus. Peromyscus sp., Perognathus parvus, y Thomomys towsendii fueron las más abundantes. El promedio estimado de masa de presa fué de 44.5 g (alcance de 20.5 a 82.6 g en nidos individuales), y la amplitud del nicho de comida (diversidad en dieta estimada por $1/\Sigma p_{{\rm i}}{}^{2}$) fué de 7.32 (alcance de 1.55 a 6.85 en nidos individuales). El mayor solapamiento en dieta ocurrío entre nidos en el mismo año que entre años en el mismo nido. Hay una correlación significativa entre especies tomadas como presa con los tipos de habitat en que el nido se localizó. La dieta de los Bubo én areas de agricultura intensiva sobrelaparon poco (42%) con aquellos en habitats salvajes.

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