Ardea
Official journal of the Netherlands Ornithologists' Union

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Caldwell C.J. (2016) Energetics of Great Egrets foraging in upland agricultural fields. ARDEA 104 (1): 69-82
I examined the foraging and diet energetics of the Great Egret across an upland landscape to compare relative costs and benefits associated with commensal, non-commensal, solitary and group foraging strategies. Across strategies, Great Egrets used a combination of different foraging modes. Net energetic gains and costs differed across strategies. Foraging costs were lower for solitary egrets, mainly as a result of decreased foraging times and lower aggression and relocation frequencies. Solitary egrets likely suffered unmeasured costs from territoriality, expensive capture efforts and handling larger prey. Group foragers accumulated higher costs due to having longer foraging times, and higher pursuit, relocation and aggression frequencies. Commensal foragers had lower overall costs in comparison to solitary and group foragers. When ranked by energetic cost-benefit ratio, solitary foraging was the most efficient strategy and group foraging strategies were the least efficient. The overall benefits from profitable food sources outweighed the estimated costs of terrestrial foraging. Great Egrets are ecologically flexible and expand their niche breadth into upland habitats where ample energy resources are apparently available. The Great Egretís ability to capitalize on different energy sources during different foraging situations likely improves foraging efficiency and energy intake over time.


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