Remisiewicz Magdalena, Underhill Les G
Bird Migration Research Station, Faculty of Biology, University of Gdańsk, Gdańsk, Poland.
Animal Demography Unit, Department of Biological Sciences, University of Cape Town, Cape Town, South Africa.
PeerJ. 2020 Mar 17;8:e8770. doi: 10.7717/peerj.8770. eCollection 2020.
The arrival of many species of migrant passerine in the European spring has shifted earlier over recent decades, attributed to climate change and rising temperatures in Europe and west Africa. Few studies have shown the effects of climate change in both hemispheres though many long-distance migrants use wintering grounds which span Africa. The migrants' arrival in Europe thus potentially reflects a combination of the conditions they experience across Africa. We examine if the timing of spring migration of a long-distance migrant, the Willow Warbler, is related to large-scale climate indices across Africa and Europe.
Using data from daily mistnetting from 1 April to 15 May in 1982-2017 at Bukowo (Poland, Baltic Sea coast), we developed an Annual Anomaly metric (AA, in days) to estimate how early or late Willow Warblers arrive each spring in relation to their multi-year average pattern. The Willow Warblers' spring passage advanced by 5.4 days over the 36 years. We modelled AA using 14 potential explanatory variables in multiple regression models. The variables were the calendar year and 13 large-scale indices of climate in Africa and Europe averaged over biologically meaningful periods of two to four months during the year before spring migration.
The best model explained 59% of the variation in AA with seven variables: Northern Atlantic Oscillation (two periods), Indian Ocean Dipole, Southern Oscillation Index, Sahel Precipitation Anomaly, Scandinavian Index and local mean temperatures. The study also confirmed that a long-term trend for Willow Warblers to arrive earlier in spring continued up to 2017.
Our results suggest that the timing of Willow Warbler spring migration at the Baltic Sea coast is related to a summation of the ecological conditions they had encountered over the previous year during breeding, migration south, wintering in Africa and migration north. We suggest these large-scale climate indices reflect ecological drivers for phenological changes in species with complex migration patterns and discuss the ways in which each of the seven climate indices could be related to spring migration at the Baltic Sea coast.
近几十年来，许多种类的欧洲春季迁徙雀形目鸟类的到来时间已提前，这归因于气候变化以及欧洲和西非气温的上升。尽管许多长途迁徙鸟类使用横跨非洲的越冬地，但很少有研究显示气候变化在两个半球的影响。因此，这些鸟类抵达欧洲的时间可能反映了它们在整个非洲所经历的综合条件。我们研究了一种长途迁徙鸟类——柳莺春季迁徙的时间是否与非洲和欧洲的大规模气候指数相关。
利用1982年至2017年4月1日至5月15日在布科沃（波兰，波罗的海沿岸）每日使用捕雾网收集的数据，我们开发了一种年度异常指标（AA，以天数计），以估计柳莺每年春天相对于其多年平均模式提前或推迟到达的时间。在这36年中，柳莺的春季迁徙提前了5.4天。我们在多元回归模型中使用14个潜在解释变量对AA进行建模。这些变量包括年份以及在春季迁徙前一年中生物学上有意义的两到四个月期间平均的13个非洲和欧洲大规模气候指数。
最佳模型用七个变量解释了AA变化的59%：北大西洋涛动（两个时期）、印度洋偶极子、南方涛动指数、萨赫勒降水异常、斯堪的纳维亚指数和当地平均温度。该研究还证实，直到2017年，柳莺春季提前到达的长期趋势仍在持续。
我们的结果表明，波罗的海沿岸柳莺春季迁徙的时间与它们上一年在繁殖、南迁、在非洲越冬和北迁过程中遇到的生态条件总和有关。我们认为这些大规模气候指数反映了具有复杂迁徙模式物种物候变化的生态驱动因素，并讨论了七个气候指数中的每一个与波罗的海沿岸春季迁徙相关的方式。
