Stable isotope analysis provides valuable insights into the ecology of long-distance migratory birds during periods spent away from a specific study site. In a previous study, Swedish great reed warblers (Acrocephalus arundinaceus) infected with haemosporidian parasites differed in feather isotope ratios compared to non-infected birds, suggesting that infected and non-infected birds spent the non-breeding season in different locations or habitats. Here, we use a novel dataset comprising geolocator data, isotopes, and haemosporidian infection status of 92 individuals from four Eurasian populations to investigate whether parasite transmission varies with geography or habitats. We found that the probability of harbouring Plasmodium and Leucocytozoon parasites was higher in birds moulting in the eastern region of the non-breeding grounds. However, no geographic pattern occurred for Haemoproteus infections or overall infection status. In contrast to the previous study, we did not find any relationship between feather isotope ratios and overall haemosporidian infection for the entire current dataset. Plasmodium-infected birds had lower feather δ¹⁵N values indicating that they occupied more mesic habitats. Leucocytozoon-infected birds had higher feather δ³⁴S values suggesting more coastal sites or wetlands with anoxic sulphate reduction. As the composition and prevalence of haemosporidian parasites differed between the old and the current dataset, we suggest that the differences might be a consequence of temporal dynamics of haemosporidian parasites. Our results emphasize the importance of replicating studies conducted on a single population over a restricted time period, as the patterns can become more complex for data from wider geographical areas and different time periods.

稳定同位素分析为长途候鸟离开特定研究地点期间的生态学提供了宝贵的见解。在之前的一项研究中，感染血孢子寄生虫的瑞典大芦苇莺（Acrocephalus arundinaceus）与未感染的鸟类相比，羽毛同位素比率不同，这表明受感染和未感染的鸟类在不同的地点或栖息地度过非繁殖季节。在这里，我们使用一个新颖的数据集，其中包括来自四个欧亚种群的 92 名个体的地理定位器数据、同位素和血孢子虫感染状态，以调查寄生虫传播是否因地理位置或栖息地而异。我们发现，在非繁殖地东部地区换羽的鸟类中，携带疟原虫和白细胞虫寄生虫的可能性较高。然而， Haemoproteus感染或总体感染状态没有出现地理模式。与之前的研究相反，我们没有发现整个当前数据集中羽毛同位素比率与总体血孢子虫感染之间的任何关系。感染疟原虫的鸟类具有较低的羽毛δ ¹⁵ N 值，表明它们占据了更湿润的栖息地。白细胞虫感染的鸟类具有较高的羽毛δ ³⁴ S 值，表明更多的沿海地区或湿地存在缺氧硫酸盐减少。由于旧数据集和当前数据集之间血孢子寄生虫的组成和流行率不同，我们认为这些差异可能是血孢子寄生虫时间动态的结果。我们的结果强调了在有限的时间段内对单个人群进行重复研究的重要性，因为对于来自更广泛的地理区域和不同时间段的数据，模式可能变得更加复杂。