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 less than 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 ca 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% of 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).

诸多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，这与"信号与响应间的滞后时长越短则可靠性越高，进而降低与猎物发生物候错配的概率"这一理论预测相符。本研究以欧洲椋鸟（Sturnus vulgaris）为研究对象，结果显示，产卵前约50~90天（即1月8日至2月22日）的隆冬气温，可极强地（决定系数r²=0.89）解释产卵日期的年际差异。隆冬气温还与相对窝卵数显著相关：在隆冬气温较低的年份，椋鸟的产卵时间更晚，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；同一年中80%的巢箱产卵时间集中在4.8天范围内），但其窝卵数和繁殖成效仍存在显著的日期依赖性变异，不过这类变异似乎由另一套整合补充信号（气温）信息的时间机制所介导。我们认为，隆冬气温与繁殖物候（breeding phenology）之间的关联可能是间接的：二者均与第三个因素相关，即椋鸟的猎物——大蚊类昆虫（tipulid）的发育进程受气温调控。隆冬气温可决定大蚊类幼虫的生长轨迹与最终生物量，这类气温信号可为椋鸟提供繁殖季猎物可获得性的相关信息（尽管具体的信号传导路径仍未明确）。