Data from: Mid-winter temperatures, not spring temperatures, predict breeding phenology in the European starling Sturnus vulgaris

In many species empirical data suggest that temperatures <1 month before breeding strongly influence laying date, consistent with predictions that short lag times between cue and response are more reliable, decreasing the chance of mismatch with prey. Here we show in European starlings (Sturnus vulgaris) that mid-winter temperature c.50-90 days before laying (8 January – 22 February) strongly (r2=0.89) predicts annual variation in laying date. Mid-winter temperature also correlated highly with relative clutch size: birds laid later, but laid larger clutches, in years when mid-winter temperatures were lower. Despite a high degree of breeding synchrony (mean laying date 5-13 April = ± 4 days; 80% nests laid within 4.8 days within-year) European starlings show strong date-dependent variation in clutch size and productivity, but this appears to be mediated by a different temporal mechanism for integration of supplemental cue (temperature) information. We suggest the relationship between mid-winter temperature and breeding phenology might be indirect with both components correlating with a third factor: temperature-dependent development of the starling’s insect (Tipulid) prey. Mid-winter temperatures might set the trajectory of growth and final biomass of Tipulid larvae, with this temperature cue providing starlings with information on breeding season prey availability (though exactly how remains unknown).多项物种的实证数据均表明，繁殖前不足1个月的气温会显著影响产卵日期，这契合“提示物与响应之间的时滞越短则可靠性越高，可降低与猎物物候错配的概率”这一理论预测。本研究以欧洲椋鸟（Sturnus vulgaris）为研究对象，发现产卵前约50至90天（1月8日至2月22日）的仲冬气温能够高度（决定系数r²=0.89）预测产卵日期的年际变化。仲冬气温还与相对窝卵数高度相关：在仲冬气温较低的年份，椋鸟产卵时间更晚，但窝卵数更大。尽管欧洲椋鸟的繁殖同步性极高（平均产卵日期为4月5日至13日，标准差±4天；年内80%的巢的产卵时间集中在4.8天内），但其窝卵数和繁殖成效仍存在显著的日期依赖性变化，而这一效应似乎由另一种整合额外提示物（气温）信息的时间机制所介导。我们认为，仲冬气温与繁殖物候之间的关联可能是间接的：二者均与第三类因素相关，即椋鸟的猎物——大蚊科（Tipulid）昆虫的发育进程受气温调控。仲冬气温或可决定大蚊幼虫的生长轨迹与最终生物量，这类气温提示物能够为椋鸟提供繁殖季猎物可获得性的相关信息（尽管具体机制仍不明晰）。