Data from: Predicting bird phenology from space: satellite-derived vegetation green-up signal uncovers spatial variation in phenological synchrony between birds and their environment

Population-level studies of how tit species (Parus spp.) track the changing phenology of their caterpillar food source have provided a model system allowing inference into how populations can adjust to changing climates, but are often limited because they implicitly assume all individuals experience similar environments. Ecologists are increasingly using satellite-derived data to quantify aspects of animals' environments, but so far studies examining phenology have generally done so at large spatial scales. Considering the scale at which individuals experience their environment is likely to be key if we are to understand the ecological and evolutionary processes acting on reproductive phenology within populations. Here, we use time series of satellite images, with a resolution of 240 m, to quantify spatial variation in vegetation green-up for a 385-ha mixed-deciduous woodland. Using data spanning 13 years, we demonstrate that annual population-level measures of the timing of peak abundance of winter moth larvae (Operophtera brumata) and the timing of egg laying in great tits (Parus major) and blue tits (Cyanistes caeruleus) is related to satellite-derived spring vegetation phenology. We go on to show that timing of local vegetation green-up significantly explained individual differences in tit reproductive phenology within the population, and that the degree of synchrony between bird and vegetation phenology showed marked spatial variation across the woodland. Areas of high oak tree (Quercus robur) and hazel (Corylus avellana) density showed the strongest match between remote-sensed vegetation phenology and reproductive phenology in both species. Marked within-population variation in the extent to which phenology of different trophic levels match suggests that more attention should be given to small-scale processes when exploring the causes and consequences of phenological matching. We discuss how use of remotely sensed data to study within-population variation could broaden the scale and scope of studies exploring phenological synchrony between organisms and their environment.

针对山雀属（Parus spp.）物种如何追踪其毛虫食物源的物候变化开展的种群水平研究，已构建出可用于推断种群如何适应气候变化的模型系统，但这类研究往往存在局限——其隐含假定所有个体所处的环境均完全一致。生态学家正愈发多地借助卫星遥感数据量化动物所处环境的各项特征，但截至目前，相关物候研究大多仅在大空间尺度上开展。若要解析作用于种群内繁殖物候的生态与进化过程，考虑个体实际感知的环境尺度无疑是关键所在。本研究借助分辨率为240米的卫星影像时间序列，对一片385公顷的落叶混交林内植被返青的空间差异进行量化。基于13年的观测数据，我们证实：冬尺蛾幼虫（Operophtera brumata）种群丰度峰值的年度发生时间，以及大山雀（Parus major）、蓝山雀（Cyanistes caeruleus）的产卵时间，均与卫星遥感反演的春季植被物候存在显著关联。后续分析进一步表明，局地植被返青时间能够显著解释种群内山雀繁殖物候的个体差异，且鸟类与植被物候的同步程度在整片林地中存在显著的空间异质性。橡树（Quercus robur）与榛树（Corylus avellana）密度较高的区域，两种山雀的遥感植被物候与繁殖物候的匹配程度均为最高。不同营养级的物候匹配程度在种群内存在显著差异，这提示我们在探究物候匹配的成因与影响时，应更多关注小尺度生态过程。本研究还讨论了借助遥感数据开展种群内变异研究，如何能够拓展物种与环境间物候同步性相关研究的尺度与范畴。