Variation in body mass dynamics among sites in Black Brant Branta bernicla nigricans supports adaptivity of mass loss during moult

摘要: Birds employ varying strategies to accommodate the energetic demands of moult, one important example being changes in body mass. To understand better their physiological and ecological significance, we tested three hypotheses concerning mass dynamics during moult. We studied Black Brant 2006 2007 moulting at sites Alaska which varied food availability, breeding status whether geese undertook a moult migration. First predicted that if loss were simply result inadequate resources then would be highest where was least available. Secondly, adaptive, allowing birds reduce activity gain prior feeding conditions allowed positively related initiation. Thirdly, regain flight sooner, across groups, end flightless period converge on theoretical optimum, i.e. permits earliest possible return flight. Mass greatest most available thus our results did not support prediction resulted from availability. initiation both availability loss. In addition, among years, variation high but greatly reduced period, appearing converge. Thus, supported multiple predictions adaptive optimal strategy through behavioural modifications use these reserves so doing also wing loading. Geese migration initiated mass, indicating they more than able compensate for cost Because frequently change between years relation success, site-specific observed suggests individual plasticity dynamics.