Anuario Ornitológico. > Anuario 1999. Vol. 6. > Variations in food composition and foraging behaviour of Grey heron in Aragon river during the breeding season |
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Variations in food composition and foraging behaviour of Grey heron in Aragon river during the breeding season |
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Anu. Ornit. de Navarra 1999. Vol. 6: 19-25. 2001. |
SUMMARYJesús Mª LEKUONAForaging strategies of Grey Herons, Ardea cinerea, in northern Spain were studied in the main feeding areas (a river) during the breeding season (March-June). In the study area, herons were mainly piscivorous both in number and biomass. Small fishes were caught more frequently by herons in March and April and medium-sized fishes were more abundant in May and June. Herons spent more time in the feeding areas in June than in May and April. The average biomass taken by adults in each foraging session was similar in June and May but greater than in April. Feeding attempts were more numerous and successful in shallow water. Intraspecific aggressions were higher in May and June than in April. Probably the hatching of chicks and their age-related requirements of food were the cause of these changes in foraging strategies. Key words: Ardea cinerea, breeding season, food composition, foraging strategies, Grey Heron, river. | |
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