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).

诸多物种的实证研究均表明，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强，可降低与猎物物候错配概率」的预测结果一致。本研究以欧椋鸟（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）的隆冬气温可显著（决定系数r²=0.89）解释产卵日期的年度变异。隆冬气温同时与相对窝卵数呈高度相关：在隆冬气温较低的年份，欧椋鸟产卵时间更晚，但窝卵数更大。尽管欧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；同年度内80%的鸟巢产卵日期均落在4.8天的区间内），但其窝卵数与繁殖成效仍存在显著的日期依赖性变异，而这一现象似乎由另一种整合补充信号（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之间的关联可能是间接的：二者均与第三类因素相关，即欧椋鸟的猎物——大蚊科昆虫（tipulid）的发育进程受气温调控。隆冬气温或可决定大蚊科幼虫的生长轨迹与最终生物量，该气温信号可为欧椋鸟提供繁殖季猎物可获得性的相关信息（尽管其具体作用机制仍有待阐明）。