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Effects of Body Size and Sex on Foraging Territoriality of the Little Egret (Egretta garzetta) in Japan

Yukiko Nota
The Auk
Vol. 120, No. 3 (Jul., 2003), pp. 791-798
DOI: 10.2307/4090109
Stable URL: http://www.jstor.org/stable/4090109
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.
Effects of Body Size and Sex on Foraging Territoriality of the Little Egret (Egretta garzetta) in Japan
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Abstract

I studied the characteristics of foraging territoriality in the Little Egret (Egretta garzetta) and effects of body size and sex on territoriality. Sixty-eight birds were captured and sexed, and foraging behavior (usage of area, defense rate, and foraging efficiency) of 26 birds identified by color bands was observed in detail for 3 years. I categorized territoriality within the foraging area into three types according to the birds' exclusiveness and attachment to the area: high exclusiveness and strong attachment to the same area for a long period, moderate exclusiveness and attachment, and minimal exclusiveness and attachment. Body size was largest and feeding efficiency was highest in the first type. I propose a model that predicts a relationship between body size and defense rate to explain the behavior of egrets. /// Estudié características de la territorialidad de forrajeo y los efectos del tamaño corporal y el sexo sobre la territorialidad en la garza Egretta garzetta. Se capturó y se determinó el sexo de un total de 68 garzas, y se estudió el comportamiento de forrajeo (uso del área, tasa de defensa y eficiencia de forrajeo) observando detalladamente 26 individuos identificados con anillos de colores durante tres años. La territorialidad dentro del área de forrajeo se categorizó en tres tipos de acuerdo a la exclusividad y apego al área por parte de las aves: (1) alta exclusividad y fuerte apego a la misma área por un período prolongado, (2) exclusividad y apego moderados, y (3) poca exclusividad y apego. El tamaño corporal y la eficiencia de forrajeo fueron máximos en aves del primer tipo. Propongo un modelo que predice la relación entre el tamaño corporal y la tasa de defensa para explicar el comportamiento de E. garzetta.

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