Shifts in timing and duration of breeding for 73 boreal bird species over four decades

Breeding timed to match optimal resource abundance is vital for the successful reproduction of species, and breeding is therefore sensitive to environmental cues. As the timing of breeding shifts with a changing climate, this may not only affect the onset of breeding, but also its termination, and thus the length of the breeding period. We use an extensive dataset of over 820K nesting records of 73 bird species across the boreal region in Finland to probe for changes in the beginning, end, and duration of the breeding period over four decades (1975-2017). We uncover a general advance of breeding with a strong phylogenetic signal, but no systematic variation over space. Additionally, 31% of species contracted their breeding period in at least one bioclimatic zone, as the end of the breeding period advanced more than the beginning. We did not detect a statistical difference in phenological responses of species with combinations of different migratory strategy or number of broods. Nonethel...将繁殖时间调整至与最佳资源丰度时段相匹配，对于物种的成功繁衍至关重要，因此繁殖行为对环境线索极为敏感。随着气候变化引发繁殖物候改变，这不仅会影响繁殖的起始时间，还会改变其终止时间，进而影响繁殖周期的总时长。我们依托芬兰境内北方针叶林带范围内73种鸟类的逾82万条筑巢记录数据集，探究了1975年至2017年这四十年间，鸟类繁殖起始时间、终止时间及繁殖周期时长的变化规律。研究发现，鸟类繁殖整体呈现提前态势，且存在显著的系统发育信号（phylogenetic signal），但在空间维度上未表现出系统性差异。此外，有31%的物种在至少一个生物气候区（bioclimatic zone）内出现繁殖周期缩短的现象，这是由于繁殖终止时间的提前幅度大于繁殖起始时间的提前幅度。我们未检测到具备不同迁徙策略（migratory strategy）或繁殖窝数（number of broods）组合的物种，其物候响应存在统计学意义上的显著差异。然而，