Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB Wageningen, The Netherlands.
Am Nat. 2012 Feb;179(2):E55-69. doi: 10.1086/663675. Epub 2011 Dec 20.
Timing of reproduction in temperate-zone birds is strongly correlated with spring temperature, with an earlier onset of breeding in warmer years. Females adjust their timing of egg laying between years to be synchronized with local food sources and thereby optimize reproductive output. However, climate change currently disrupts the link between predictive environmental cues and spring phenology. To investigate direct effects of temperature on the decision to lay and its genetic basis, we used pairs of great tits (Parus major) with known ancestry and exposed them to simulated spring scenarios in climate-controlled aviaries. In each of three years, we exposed birds to different patterns of changing temperature. We varied the timing of a temperature change, the daily temperature amplitude, and the onset and speed of a seasonal temperature rise. We show that females fine-tune their laying in response to a seasonal increase in temperature, whereas mean temperature and daily temperature variation alone do not affect laying dates. Luteinizing hormone concentrations and gonadal growth in early spring were not influenced by temperature or temperature rise, possibly posing a constraint to an advancement of breeding. Similarities between sisters in their laying dates indicate genetic variation in cue sensitivity. These results refine our understanding of how changes in spring climate might affect the mismatch in avian timing and thereby population viability.
温带鸟类的繁殖时间与春季温度密切相关，温暖年份的繁殖开始时间更早。雌性会根据年份调整产卵时间，使其与当地的食物来源同步，从而优化繁殖产出。然而，气候变化目前破坏了预测环境线索与春季物候之间的联系。为了研究温度对产卵决策的直接影响及其遗传基础，我们使用了具有已知亲缘关系的成对大山雀（Parus major），并将它们暴露在气候控制的鸟舍中的模拟春季场景中。在三年中的每一年，我们都让鸟类暴露于不同的温度变化模式中。我们改变了温度变化的时间、每日温度幅度以及季节性温度上升的开始和速度。我们表明，雌性会根据季节性温度升高来微调产卵时间，而平均温度和每日温度变化本身并不会影响产卵日期。春季早期的促黄体激素浓度和性腺生长不受温度或温度上升的影响，这可能限制了繁殖的提前。姐妹之间产卵日期的相似性表明，对线索的敏感性存在遗传变异。这些结果细化了我们对春季气候变化如何影响鸟类时间失配以及种群活力的理解。
