The Christiansø colony of common eiders (Somateria mollissima) in the central Baltic Sea were exposed to high levels of Pb during the 2018 breeding season that were not present in 2017. Due to these high Pb blood levels, the present study investigated possible Pb sources and Pb dynamics within this vulnerable colony. We analyzed body mass and lead isotopic ratios (Pb-IRs) in blood taken from the same incubating eiders at the early (day 4) and late (day 24) stages of incubation during the 2018 breeding season (n = 23). Pb-IRs 208/207, 208/206, 206/207, and 207/206 were analyzed using high resolution inductively coupled mass spectrometry. We found largely similar Pb-IRs from the different stages of incubation indicating a predominantly constant endogenous source of Pb exposure. We suggest the increasing Pb levels come from pre-nesting and nesting foraging and from medullary bone release. The similar Pb-IRs also indicate continued metabolization of the medullary bone to meet the nutritional and energy demands of incubation. Comparisons to Pb-IR reports from the Baltic Sea showed multiple sources of pollution distinguished by a difference between Pb-IRs in individuals with Pb blood concentrations >500 μg/kg ww and <500 μg/kg ww. The most highly contaminated individuals in the present study had Pb-IRs similar to those of Pb ammunition indicating shot pellet uptake. This study further emphasizes the need for continued biomonitoring of the Christiansø colony, including fecal sampling and environmental field sampling to identify the origin and extent of dietary Pb exposure on Christiansø. As a representative unit of the Baltic Flyway population; the Christiansø colony provides an important opportunity for continued investigation into Pb contamination, population dynamics, and declines.

Christiansø殖民地的常见绒毛（Somateria mollissima）在波罗的海中部，在2018年繁殖季节期间暴露于高水平的Pb，而2017年则不存在。由于这些高Pb血液水平，本研究调查了该脆弱群体内可能的Pb来源和Pb动态。我们分析了在2018繁殖季节（n = 23）的孵化早期（第4天）和后期（第24天）从相同孵化绒毛中抽取的血液中的体重和铅同位素比（Pb-IRs）。使用高分辨率电感耦合质谱仪分析了Pb-IR 208 / 207、208 / 206、206 / 207和207/206。我们从不同的孵化阶段发现了许多相似的Pb-IR，这表明Pb暴露主要是恒定的内源性来源。我们建议增加的Pb水平来自于巢前和巢状觅食以及髓质骨的释放。相似的Pb-IRs也表明髓质骨继续代谢，以满足孵化的营养和能量需求。与波罗的海的Pb-IR报告进行比较后发现，Pb血药浓度> 500μg/ kg ww和<500μg/ kg ww的个体中，Pb-IR之间存在差异。在本研究中，受污染最严重的个体的Pb-IR与Pb弹药相似，表明弹丸被摄取。这项研究进一步强调了需要对克里斯蒂安氏菌落进行持续的生物监测，包括粪便采样和环境田间采样，以鉴定克里斯蒂安氏菌的饮食中铅暴露的来源和程度。作为波罗的海飞行人口的代表单位；