School of Biological Sciences, Monash University, Melbourne, Vic., Australia.
Max Planck Institute for Ornithology, Radolfzell, Germany.
J Anim Ecol. 2019 Nov;88(11):1799-1811. doi: 10.1111/1365-2656.13068. Epub 2019 Aug 12.
Changes in climate are shifting the timing of life cycle events in the natural world. Compared to northern temperate areas, these effects are relatively poorly understood in tropical and southern regions, where there is limited information on how timing of breeding and food availability are affected by climatic factors, and where patterns of breeding activity are more unpredictable within and between years. Combining a new statistical modelling approach with 5 years of continuous individual-based monitoring of a monsoonal tropical insectivorous bird, we quantified (a) the proximate climatic drivers at two trophic levels: timing of breeding and abundance of arthropod prey; (b) the effect of climate variation on reproductive output and (c) the role of individual plasticity. Rainfall was identified as the main determinant of phenology at both trophic levels. Throughout the year, likelihood of egg laying increased very rapidly in response to even small amounts of rain during the preceding 0-3 weeks. Adult body mass and male sperm storage also increased rapidly after rain, suggesting high breeding preparedness. Additionally, females were flexible, since they were more likely to nest whether their previous attempt was longer ago and unsuccessful. Arthropod abundance also increased after rainfall, but more slowly, with a peak around 10 weeks. Therefore, the peak food availability coincided with the presence of dependent fledglings. Fitness benefits of nesting after more rain appeared to be linked to offspring quantity rather than quality: nest attempts following higher rainfall produced larger clutches, but showed no improvement in nestling mass or relative fledging success. The response of clutch size to rainfall was plastic, since repeated sampling showed that individual females laid larger clutches after more rain, possibly mediated by improved body mass. Rapid, individually flexible breeding in response to rainfall and slower increase in arthropod abundance also as a response to rainfall, might buffer insectivorous species living in tropical seasonal environments from climate change-induced phenological trophic mismatches.
气候变化正在改变自然界中生命周期事件的时间。与北方温带地区相比，热带和南半球对这些影响的了解相对较少，这些地区关于繁殖时间和食物供应如何受到气候因素的影响的信息有限，而且繁殖活动的模式在年内和年际之间更加不可预测。我们结合了一种新的统计建模方法和对一种季风热带食虫鸟类进行的 5 年连续个体监测，定量了（a）两个营养级的近似气候驱动因素：繁殖时间和节肢动物猎物的丰度；（b）气候变化对繁殖输出的影响；（c）个体可塑性的作用。降雨被确定为两个营养级的物候学的主要决定因素。全年，在之前的 0-3 周内，即使降雨量很小，产卵的可能性也会迅速增加。雨水过后，成鸟的体重和雄性精子储存量也迅速增加，表明繁殖准备度很高。此外，由于前一次繁殖尝试的时间较长且不成功，雌性变得更加灵活，因此更容易筑巢。雨后节肢动物的丰度也会增加，但速度较慢，峰值出现在大约 10 周后。因此，食物供应的高峰期与有依赖性的雏鸟的存在相吻合。在更多雨后筑巢的好处似乎与后代的数量而不是质量有关：雨后更多的降雨量会产生更大的巢，但在巢雏的体重或相对育雏成功率方面没有提高。对降雨量的产卵大小的反应是具有可塑性的，因为重复采样表明，个体雌鸟在降雨量更大后会产下更大的卵，这可能是通过改善体重来介导的。对降雨的快速、个体灵活的繁殖反应，以及对降雨的较慢的节肢动物丰度增加，也可能使生活在热带季节性环境中的食虫物种免受气候变化引起的物候营养不匹配的影响。
