Information on nest-activity patterns and energetic costs during the breeding season may shed light on current population trends of Great Egrets (Ardea alba). To address the issue, Great Egrets nesting in a mixed species colony in Wichita, Kansas, were studied from May–July in 2008 and 2009. A total of 35 h of scan samples at 28 random nests resulted in 5,062 instantaneous records; a separate 62 h of observations recorded 75 food-provisioning intervals. Adults at the nest engaged mainly in low-cost activities such as sitting, standing and preening, but activity patterns differed significantly by nest content. Adults with eggs spent significantly more time sitting but less time standing, preening or away from the nest. Overall variation in activity patterns among the 28 study nests was not significant. Food-provisioning intervals ranged from 6-480 min, with a median duration of 180 min. Intervals declined significantly with chick stage, were longer during periods of high wind velocity, and varied by time of day. Food-provisioning intervals for adults with eggs averaged >80 min longer than for those with chicks of all sizes. The results suggest that Great Egrets engage in low-cost activities and minimize energy costs while at the nest, and adjust the pattern of food-provisioning trips in response to proximate conditions and increased food demand.
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Vol. 33 • No. 4