The timing of breeding often has a profound influence on the reproductive success of birds living in seasonal environments with rapidly changing nestling food availability. Timing is typically investigated with reference to lay dates, but it is the time of hatching that determines the ambient conditions and food availability that nestlings experience. Thus, in addition to lay date, phenological studies may also have to take account of variation in the length of the incubation period, which is likely to depend on both environmental conditions and parental traits. The primary aim of this study was to use a 24-year dataset to investigate the abiotic and biotic factors influencing variation in incubation duration in long-tailed tits (Aegithalos caudatus), a species in which incubation duration varies substantially (range: 12–26 days). We found support for our predictions that drier conditions, later breeding attempts and larger clutches were associated with shorter incubation periods. Larger clutches were also more resilient to increases in incubation duration associated with wet conditions. Surprisingly, warmer ambient conditions were associated with longer incubation periods. Secondly, we assessed the consequences of variation in the length of incubation periods for the risk of nest predation and the hatching success of surviving clutches. We show that longer incubation periods are likely to be costly due to increased exposure to nest predators. In contrast, we found only marginal effects of environmental conditions or incubation duration on hatching success, implying that wet conditions cause slower embryo growth and hence longer incubation periods, rather than causing embryo fatality. We suggest that long-tailed tits’ nests and parental behavior protect eggs from mortality arising directly from adverse weather conditions.

中文翻译：

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在温带雀形目中孵化：环境条件会影响孵化期的持续时间和孵化成功吗？

繁殖的时间通常对生活在季节性环境中的鸟类的繁殖成功有深远的影响，雏鸟的食物供应迅速变化。通常参考产蛋日期调查时间，但孵化时间决定了雏鸟经历的环境条件和食物供应。因此，除了产蛋日期，物候研究还可能必须考虑潜伏期长度的变化，这可能取决于环境条件和亲本特征。本研究的主要目的是使用 24 年的数据集来研究影响长尾山雀（Aegithalos caudatus）孵化时间变化的非生物和生物因素，该物种的孵化时间变化很大（范围：12-26天）。我们发现支持我们的预测，即较干燥的条件、较晚的繁殖尝试和较大的离合器与较短的潜伏期有关。较大的离合器也更能适应与潮湿条件相关的孵化持续时间的增加。令人惊讶的是，较温暖的环境条件与较长的潜伏期有关。其次，我们评估了孵化期长度变化对巢穴捕食风险和幸存离合器孵化成功的影响。我们表明，由于越来越多地暴露于巢穴捕食者，更长的潜伏期可能会付出代价。相比之下，我们发现环境条件或孵化时间对孵化成功的影响很小，这意味着潮湿的条件会导致胚胎生长缓慢，因此孵化期更长，而不是导致胚胎死亡。我们建议长尾山雀的巢穴和父母的行为可以保护鸡蛋免受不利天气条件直接导致的死亡。