Institute of Evolutionary Biology, The University of Edinburgh, The King's Buildings, Edinburgh EH9 3FL, UK.
British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK.
Proc Biol Sci. 2019 Aug 14;286(1908):20190952. doi: 10.1098/rspb.2019.0952.
Establishing the cues or constraints that influence avian timing of breeding is the key to accurate prediction of future phenology. This study aims to identify the aspects of the environment that predict the timing of two measures of breeding phenology (nest initiation and egg laying date) in an insectivorous woodland passerine, the blue tit (Cyanistes caeruleus). We analyse data collected from a 220 km, 40-site transect over 3 years and consider spring temperatures, tree leafing phenology, invertebrate availability and photoperiod as predictors of breeding phenology. We find that mean night-time temperature in early spring is the strongest predictor of both nest initiation and lay date and suggest this finding is most consistent with temperature acting as a constraint on breeding activity. Birch budburst phenology significantly predicts lay date additionally to temperature, either as a direct cue or indirectly via a correlated variable. We use cross-validation to show that our model accurately predicts lay date in two further years and find that similar variables predict lay date well across the UK national nest record scheme. This work refines our understanding of the principal factors influencing the timing of tit reproductive phenology and suggests that temperature may have both a direct and indirect effect.
确定影响鸟类繁殖时间的线索或限制因素是准确预测未来物候的关键。本研究旨在确定环境的哪些方面可以预测两种繁殖物候（筑巢开始和产卵日期）的时间，这两种物候分别在食虫林地雀形目鸟类蓝山雀（Cyanistes caeruleus）身上得到了体现。我们分析了来自 3 年 40 个站点、220 公里的横断线上的数据，将春季温度、树木叶龄期、无脊椎动物的可利用性和光照时间作为繁殖物候的预测因子。我们发现，早春时的平均夜间温度是筑巢开始和产卵日期的最强预测因子，这一发现表明温度对繁殖活动的限制作用最明显。桦树芽期的物候期显著预测了产卵日期，这既可以作为直接线索，也可以通过相关变量间接预测。我们使用交叉验证来表明，我们的模型可以准确地预测另外两年的产卵日期，并且发现相似的变量在英国全国巢记录计划中也能很好地预测产卵日期。这项工作细化了我们对影响山雀繁殖物候时间的主要因素的理解，并表明温度可能具有直接和间接的影响。
