Data from: Shifts in hatch dates do not provide pied flycatchers with a rapid ontogenetic route to adjust offspring time schedules to climate change

1. Environments change rapidly, and it is unclear whether organisms with complex life-styles, such as avian migrants, are able to adjust sufficiently. For understanding human impacts on ecosystem functioning, it is crucial to understand how well, and by which mechanisms species are able to adapt.
2. To improve the understanding of migrants’ ability to adjust their annual timing to climate change, we investigated ontogenetic hatch date effects on adult spring migration timing and female egg laying dates. We experimentally delayed hatch dates of pied flycatchers Ficedula hypoleuca by one week in three breeding seasons by delaying incubation onset. We investigate if natural and experimental (shifts in) hatch date affected timing of recruiting individuals up to at least three years after the manipulation.
3. Spring arrival dates were positively correlated to natural variation in hatch dates in three of the five years considered, but no such effects were found in egg laying. Experiments showed that delayed hatching resulted in delayed arrival and laying only in one-year old and not in older birds. These effects were mostly observed during one of the study years.
4. The discrepancy between experimental and natural hatch date effects indicate that a causal hatch date effect is not generally responsible for the correlation between hatch date and timing during adulthood. Instead, we propose that natural hatch date effects on spring arrival arise from genetic variation in migration schedules, while delays in hatching induced carry-over effects on arrival and laying dates in offspring (e.g. the experimental effect in 2010). Strong support for year-specific expression of hatch date and delay effects on time schedules imply that trait-variation can be easily obscured. The latter may explain the lack of hatch date effects on female egg laying.
5. Our results imply that plasticity in breeding phenology does not provide pied flycatchers with a non-genetic inheritance route to rapidly advance annual cycles. Instead, plasticity may rather masks (genetic) trait-variation for selection to act on, and thereby slow down micro-evolutionary adaptation to changing environments.

1. 环境变化速率日益加快，诸如候鸟这类具有复杂生活史的生物是否能够做出充分的适应性调整，目前尚不明确。为厘清人类活动对生态系统功能的影响，探明物种的适应能力及其背后的作用机制至关重要。
2. 为深入理解候鸟如何调整其年度活动节律以适应气候变化，我们探究了个体发育层面的出雏日期对成鸟春季迁徙时间以及雌鸟产卵日期的影响。我们在三个繁殖季中，通过延迟孵化启动时间，将斑姬鹟（Ficedula hypoleuca）的出雏日期实验性延后一周。本研究旨在探明自然状态下与实验操控（出雏日期偏移）产生的出雏日期，是否会对实验处理后至少三年内的种群补充个体的活动节律产生影响。
3. 在所研究的五个年份中，有三个年份的春季抵达日期与自然出雏日期的变异呈正相关，但在产卵日期上未发现此类关联。实验结果显示，出雏延后仅会导致1龄个体的抵达与产卵时间延迟，对老龄个体无此影响，且此类效应仅在其中一个研究年份中被观测到。
4. 实验与自然出雏日期效应之间的差异表明，出雏日期对成体活动节律的相关性并非普遍存在因果性的出雏日期影响。我们提出，自然状态下出雏日期对春季抵达的影响源于迁徙节律的遗传变异，而出雏延迟会对子代的抵达与产卵日期产生残留效应（例如2010年的实验效应）。出雏日期与延迟效应在节律调控上呈现年份特异性表达的有力证据，意味着性状变异极易被掩盖。这一结论或可解释雌鸟产卵日期未受出雏日期影响的现象。
5. 本研究结果表明，斑姬鹟的繁殖物候可塑性并未为其提供一条非遗传遗传途径，以快速推进年度生活周期节律。相反，物候可塑性反而可能掩盖了可供选择作用的（遗传）性状变异，进而减缓种群针对环境变化的微进化适应进程。