Meller Kalle, Vähätalo Anssi V, Hokkanen Tatu, Rintala Jukka, Piha Markus, Lehikoinen Aleksi
The Helsinki Lab of Ornithology, The Finnish Museum of Natural History, University of Helsinki, PO Box 17, FI-00014 , Helsinki, Finland.
Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, FI-40014, Jyväskylä, Finland.
J Anim Ecol. 2016 Mar;85(2):570-80. doi: 10.1111/1365-2656.12486. Epub 2016 Feb 4.
Partial migration - a part of a population migrates and another part stays resident year-round on the breeding site - is probably the most common type of migration in the animal kingdom, yet it has only lately garnered more attention. Theoretical studies indicate that in partially migratory populations, the proportion of resident individuals (PoR) should increase in high latitudes in response to the warming climate, but empirical evidence exists for few species. We provide the first comprehensive overview of the environmental factors affecting PoR and the long-term trends in PoR by studying 27 common partially migratory bird species in Finland. The annual PoR values were calculated by dividing the winter bird abundance by the preceding breeding abundance. First, we analysed whether early-winter temperature, winter temperature year before or the abundance of tree seeds just before overwintering explains the interannual variation in PoR. Secondly, we analysed the trends in PoR between 1987 and 2011. Early-winter temperature explained the interannual variation in PoR in the waterbirds (waterfowl and gulls), most likely because the temperature affects the ice conditions and thereby the feeding opportunities for the waterbirds. In terrestrial species, the abundance of seeds was the best explanatory variable. Previous winter's temperature did not explain PoR in any species, and thus, we conclude that the variation in food availability caused the interannual variation in PoR. During the study period, PoR increased in waterbirds, but did not change in terrestrial birds. Partially migratory species living in physically contrasting habitats can differ in their annual and long-term population-level behavioural responses to warming climate, possibly because warm winter temperatures reduce ice cover and improve the feeding possibilities of waterbirds but do not directly regulate the food availability for terrestrial birds.
部分迁徙——即一部分种群迁徙，而另一部分全年留在繁殖地——可能是动物界最常见的迁徙类型，但直到最近才受到更多关注。理论研究表明，在部分迁徙的种群中，随着气候变暖，留居个体的比例（PoR）在高纬度地区应该会增加，但很少有物种有实证证据。通过研究芬兰的27种常见部分迁徙鸟类，我们首次全面概述了影响PoR的环境因素以及PoR的长期趋势。年度PoR值通过将冬季鸟类数量除以前一年的繁殖数量来计算。首先，我们分析了初冬温度、前一年冬季温度或越冬前树木种子的丰度是否能解释PoR的年际变化。其次，我们分析了1987年至2011年期间PoR的趋势。初冬温度解释了水鸟（水禽和海鸥）PoR的年际变化，很可能是因为温度影响冰情，从而影响水鸟的觅食机会。在陆栖物种中，种子丰度是最佳解释变量。前一年冬季的温度在任何物种中都无法解释PoR，因此，我们得出结论，食物可获得性的变化导致了PoR的年际变化。在研究期间，水鸟的PoR增加了，但陆栖鸟类没有变化。生活在物理环境不同栖息地的部分迁徙物种，其对气候变暖的年度和长期种群水平行为反应可能不同，这可能是因为温暖的冬季温度减少了冰盖，改善了水鸟的觅食可能性，但没有直接调节陆栖鸟类的食物可获得性。
