Abstract

The increase in the average air temperature due to global warming has produced an early onset of the reproduction in many migratory birds of the Paleartic region. According to the “mismatch hypothesis” this response can lead to a decrease in the breeding output when the conditions that trigger the departure from the wintering areas do not match the availability of food resources in the breeding ground. We used 653 brooding events registered during the period 1991–2013 to investigate the link between climatic variables and individual breeding performance of a partially migratory passerine, the Rock Sparrow Petronia petronia, breeding at the altitude limit of its distribution. The laying date (LD) of the earliest first clutch was associated with local spring (minimum) temperatures but did not show a significant trend during the period considered. The LD of the latest first clutch had a positive and statistically significant trend, unrelated to local covariates and resulting in a longer breeding season (∼1.5 days/year). A longer breeding season allowed birds to produce more second clutches, which proportion increased from 0.14 to 0.25. The average breeding success was also positively correlated with the average temperature in July and with the duration of the breeding season. Contrary to expectations, the most important climate-dependent effect was a stretch of the breeding season due to a significant increase of the LD of the latest first-clutches rather than an earlier breeding onset. We show how climate changes act on bird populations through multiple paths and stress the need to assess the link between climatic variables and several aspects of the breeding cycle.

中文翻译：

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气候变暖导致了繁殖季节的延长和雀形目在其海拔极限繁殖的第二窝的增加

摘要

由于全球变暖导致平均气温升高，导致古地区许多候鸟的繁殖提前开始。根据“不匹配假设”，当触发离开越冬区的条件与繁殖地的食物资源不匹配时，这种反应可能导致繁殖产量下降。我们使用 1991 年至 2013 年期间记录的 653 次育雏事件来研究气候变量与部分迁徙雀形目雀形目雀（Rock Sparrow Petronia petronia ）的个体繁殖表现之间的联系，在其分布的海拔高度范围内繁殖。最早的第一个离合器的产蛋日期（LD）与当地春季（最低）温度有关，但在所考虑的时期内没有显示出明显的趋势。最新的第一个离合器的 LD 具有积极且具有统计学意义的趋势，与局部协变量无关，并导致繁殖季节更长（~1.5 天/年）。更长的繁殖季节允许鸟类产生更多的第二窝，这一比例从 0.14 增加到 0.25。平均繁殖成功率也与七月的平均气温和繁殖季节的持续时间呈正相关。与预期相反，最重要的气候相关影响是繁殖季节的延长，这是由于最新的第一离合器的 LD 显着增加，而不是较早的繁殖开始。我们展示了气候变化如何通过多种途径对鸟类种群产生影响，并强调需要评估气候变量与繁殖周期的几个方面之间的联系。