Data from: Altered breeding biology of the European blackbird under artificial light at night

Artificial light at night (LAN) has become a stressor of global extent. Previous work has highlighted the high potential of LAN to interfere with annual and diel rhythms of seasonal organisms as well as to affect interactions at the community level. However, our understanding how LAN induced alterations of activity and breeding cycles affect the reproductive outcome and fitness of the birds is still limited. Here, we focus on the effects of night time illumination on the breeding biology of urban European blackbirds (Turdus merula). Our results indicate that blackbirds prefer illuminated nest sites and advance their date of clutch initiation by 6 days per 1 lux of night time illumination. Furthermore, daily nest survival rates increased with increasing LAN although this effect was most pronounced for the transition from dark to slightly illuminated sites. We suggest that blackbirds breeding under low artificial night light conditions benefit from the LAN-avoidance of their major predators (nocturnal) whereas predominant predators of blackbirds nesting in the city centre are diurnal and are, thus, not affected by LAN. Hence, it seems likely that both direct effects of LAN on the timing of reproduction as well as indirect effects on interspecific interactions might contribute to the observed changes in the breeding biology of European blackbirds.This study emphasizes the diverse ecological effects of the night time illumination which are – in its complexity – still poorly understood.夜间人工光（Artificial Light at Night, LAN）已成为全球性环境胁迫因子。既往研究已证实，LAN极易干扰季节性生物的年度节律与昼夜节律，同时还会影响群落层面的种间互作。然而，目前学界对LAN引发的活动与繁殖周期改变如何影响鸟类的繁殖成效与适合度的认知仍较为有限。本研究聚焦夜间光照对城市欧乌鸫（Turdus merula）繁殖生物学的影响。研究结果显示，欧乌鸫偏好光照充足的巢址，且每增加1勒克斯的夜间光照，其窝卵起始日期便会提前6天；此外，巢的每日存活率随LAN强度升高而上升，但这一效应在从黑暗到轻度光照的巢址过渡阶段最为显著。我们推测，在低强度夜间人工光环境下繁殖的欧乌鸫，可借助其主要夜行捕食者规避光照区域的特性获得生存优势；而城市中心欧乌鸫的主要捕食者为昼行性物种，因此不受LAN影响。由此可见，LAN对繁殖时序的直接影响，以及对种间互作的间接影响，二者或共同促成了本次研究中观测到的欧乌鸫繁殖生物学特征改变。本研究凸显了夜间光照所具备的多样生态效应，而这些效应因其复杂性至今仍未被充分认知。