Assessing costs of carrying geolocators using feather corticosterone in two species of aerial insectivore

Despite benefits of using light-sensitive geolocators to track animal movements and describe patterns of migratory connectivity, concerns have been raised about negative effects of these devices, particularly in small species of aerial insectivore. Geolocators may act as handicaps that increase energetic expenditure, which could explain reported effects of geolocators on survival. We tested this ‘Energetic Expenditure Hypothesis’ in 12 populations of tree swallows (Tachycineta bicolor) and barn swallows (Hirundo rustica) from North America and Europe, using measurements of corticosterone from feathers (CORTf) grown after deployment of geolocators as a measure of physiology relevant to energetics. Contrary to predictions, neither among- (both species) nor within-individual (tree swallows only) levels of CORTf differed with respect to instrumentation. Thus, to the extent that CORTf reflects energetic expenditure, geolocators apparently were not a strong handicap for birds that returned po...

尽管利用光敏地理定位器（light-sensitive geolocators）追踪动物移动、刻画迁徙连通模式具备显著优势，但这类设备的负面影响仍引发诸多担忧，尤其针对小型食虫飞行动物类群。地理定位器可能成为一种附加负担，增加机体能量消耗，这或可解释此前报道中地理定位器对鸟类存活率产生的影响。我们针对源自北美与欧洲的12个树燕（Tachycineta bicolor）和家燕（Hirundo rustica）种群，验证了这一“能量消耗假说”（Energetic Expenditure Hypothesis）：通过检测佩戴地理定位器后新生羽毛中的皮质酮（corticosterone，CORTf）水平，作为能量代谢相关生理状态的量化指标。与研究假设相悖的是，无论是跨种群水平（两个物种均呈现此结果），还是个体内水平（仅针对树燕），羽毛皮质酮水平均未因佩戴设备出现显著差异。据此而言，若羽毛皮质酮水平能够反映机体能量消耗情况，那么地理定位器显然并未对成功返回的鸟类造成显著负担……