Data from: Simulated moult reduces flight performance but overlap with breeding does not affect breeding success in a long-distance migrant

1. Long-distance migrants are time-constrained as they need to incorporate many annual cycle stages within a year. Migratory passerines moult in the short interval between breeding and migration. To widen this interval, moult may start while still breeding, but this results in flying with moulting wings when food provisioning. 2. We experimentally simulated wing gaps in breeding male pied flycatchers by plucking 2 primary feathers from both wings. We quantified the nest visitations of both parents, proportion of high-quality food brought to the nestlings and adults and nestlings condition. Differences in oxidative damage caused by a possible reduction in flight efficiency were measured in amounts of ROMs and OXY in the blood. We also measured how flight performance was affected with recordings of the male`s escape flight using high-speed cameras. Finally, we collected data on adult survival, clutch size and laying date in the following year. 3. “Plucked” males travelled a 5% shorter distance per wingbeat, showing that our treatment reduced flight performance. In line with this, “plucked” males visited their nests less often. Females of “plucked” males, however, visited the nest more often than controls, and fully compensated their partner’s reduced visitation rate. As a result, there were no differences between treatments in food quality brought to the nest, adult or chick mass or number of successfully fledged chicks. Males did not differ in their oxidative damage or local survival to the following year. In contrast, females paired with plucked males tended to return less often to breed in the next year in comparison to controls, but this difference was not significant. For the birds that did return there were no effects on breeding. 5. Our results reveal that wing gaps in male pied flycatchers reduce their flight performance, but when it occurs during breeding they prioritise their future reproduction by reducing parental care. As a result, there is no apparent detriment to their condition during breeding. Because non-moulting females are able to compensate their partner’s reduced care, there is also no immediate costs to the offspring, but females may pay the cost suffering from a reduced survival.1. 长距离迁徙鸟类受时间约束，需在一年内完成多个年度周期阶段。迁徙性雀形目鸟类的换羽过程发生在繁殖与迁徙之间的短暂窗口期。为延长该窗口期，部分个体可能在繁殖期间便开始换羽，但这会导致其在育雏阶段仍需使用正在换羽的翅膀进行飞行。 2. 本研究通过拔除繁殖期雄性斑姬鹟（pied flycatcher）两翼各2枚初级飞羽（primary feathers），实验模拟了其翅羽缺损状态。我们量化了双亲的育雏访巢频次、送往雏鸟的优质食物占比，以及成鸟与雏鸟的身体状况。针对飞行效率下降可能引发的氧化损伤差异，我们通过检测血液中活性氧代谢物（ROMs, reactive oxygen metabolites）与抗氧化指标（OXY）的含量进行了评估。此外，我们利用高速摄像机（high-speed cameras）记录雄性斑姬鹟的逃逸飞行过程，以分析其飞行性能受影响的情况。最后，我们收集了次年成鸟存活率、窝卵数（clutch size）及产卵日期（laying date）的相关数据。 3. “拔羽组”雄性斑姬鹟每次振翅的飞行距离较对照组缩短5%，证实我们的实验处理确实降低了其飞行性能。与之相符的是，拔羽组雄鸟的育雏访巢频次显著降低。然而，与拔羽组雄鸟配对的雌鸟访巢频次却高于对照组雌鸟，完全弥补了伴侣访巢频次不足的问题。最终，两组间在送往巢中的食物质量、成鸟与雏鸟体重，以及成功出巢的雏鸟数量上均无显著差异。拔羽组雄鸟的氧化损伤水平与次年本地存活率均与对照组无显著差异。与之相反，与拔羽组雄鸟配对的雌鸟次年返回繁殖地的概率略低于对照组，但该差异未达到统计学显著性水平。对于成功返回的个体而言，其繁殖表现未受显著影响。 5. 本研究结果表明，雄性斑姬鹟的翅羽缺损会降低其飞行性能，但在繁殖期发生该情况时，它们会通过减少育雏投入来优先保障未来的繁殖机会。因此，繁殖期内其身体状况并未出现明显损害。由于未换羽的雌鸟能够弥补伴侣育雏投入的不足，雏鸟也未因此受到即时的生存成本，但雌鸟可能会因自身存活率下降而承担相应代价。