The Baltic/Wadden Sea Flyway of common eiders has declined over the past three decades. Multiple factors such as contaminant exposure, global warming, hunting, white-tailed eagle predation, decreased agricultural eutrophication and infectious diseases have been suggested to explain the decline. We collected information on body mass, mercury (Hg) concentration, biochemistry and untargeted metabolomics of incubating birds in two colonies in the Danish Straits (Hov Røn, n = 100; Agersø, n = 29) and in one colony in the Baltic proper (Christiansø, n = 23) to look into their metabolisms and energy balance. Body mass was available from early and late incubation for Hov Røn and Christiansø, showing a significant decline (25–30%) in both colonies with late body mass at Christiansø being the lowest. Whole blood concentrations of total mercury Hg were significantly higher in birds at Christiansø in the east compared to Hov Røn in the west. All birds in the three colonies had Hg concentrations in the range of ≤1.0 μg/g ww, which indicates that the risk of effects on reproduction is in the no to low risk category for wild birds. Among the biochemical measures, glucose, fructosamine, amylase, albumin and protein decreased significantly from early to late incubation at Hov Røn and Christiansø, reflecting long-term fastening as supported by the decline in body mass. Untargeted metabolomics performed on Christiansø eiders revealed presence of 8,433 plasma metabolites. Of these, 3,179 metabolites changed significantly (log₂-fold change ≥1, p ≤ 0.05) from the early to late incubation. For example, smaller peptides and vitamin B₂ (riboflavin) were significantly down-regulated while 11-deoxycorticosterone and palmitoylcarnitine were significantly upregulated. These results show that cumulative stress including fasting during incubation affect the eiders’ biochemical profile and energy metabolism and that this may be most pronounced for the Christiansø colony in the Baltic proper. This amplify the events of temperature increases and food web changes caused by global warming that eventually accelerate the loss in body weight. Future studies should examine the relationship between body condition, temperature and reproductive outcomes and include mapping of food web contaminant, energy and nutrient content to better understand, manage and conserve the populations.

在过去的三十年中，常见绒毛的波罗的海/瓦登海航道有所减少。已提出多种因素来解释这种下降，例如污染物暴露，全球变暖，狩猎，白尾鹰捕食，农业富营养化程度降低和传染病。我们收集了在丹麦海峡的两个殖民地（HovRøn，n = 100；Agersø，n = 29）和波罗的海的一个殖民地（HovRøn，n = 29）中有关鸟类的体重，汞（Hg）浓度，生物化学和非靶向代谢组学信息。 Christiansø，n = 23），研究他们的新陈代谢和能量平衡。HovRøn和Christiansø的早期和晚期孵化可得到体重，两个菌落均显示出显着下降（25–30％），而Christiansø的后期体重最低。与西部的HovRøn相比，东部的Christiansø的鸟类的全血总汞Hg浓度明显更高。这三个殖民地中的所有鸟类的Hg浓度均在≤1.0μg/ g ww的范围内，这表明野生鸟类对繁殖影响的风险处于从低到低的类别。在生化措施中，从HovRøn和Christiansø孵化的早期到晚期，葡萄糖，果糖，淀粉酶，白蛋白和蛋白质显着下降，这反映了由于体重下降而长期固定。在Christiansø羽绒被上进行的非靶向代谢组学显示，存在8,433种血浆代谢物。其中3,179种代谢物发生了显着变化（log 这三个殖民地中的所有鸟类的Hg浓度均在≤1.0μg/ g ww的范围内，这表明野生鸟类对繁殖影响的风险处于从低到低的类别。在生化措施中，从HovRøn和Christiansø孵化的早期到晚期，葡萄糖，果糖，淀粉酶，白蛋白和蛋白质显着下降，这反映了由于体重下降而长期固定。在Christiansø羽绒被上进行的非靶向代谢组学显示，存在8,433种血浆代谢物。其中3,179种代谢物发生了显着变化（log 这三个殖民地中的所有鸟类的Hg浓度均在≤1.0μg/ g ww的范围内，这表明野生鸟类对繁殖影响的风险处于从低到低的类别。在生化措施中，从HovRøn和Christiansø孵化的早期到晚期，葡萄糖，果糖，淀粉酶，白蛋白和蛋白质显着下降，这反映了由于体重下降而长期固定。在Christiansø羽绒被上进行的非靶向代谢组学显示，存在8,433种血浆代谢物。其中3,179种代谢物发生了显着变化（log 从HovRøn和Christiansø孵化的早期到晚期，白蛋白和蛋白质显着下降，这反映了体重下降的支持，可以长期固定。在Christiansø羽绒被上进行的非靶向代谢组学显示，存在8,433种血浆代谢物。其中3,179种代谢物发生了显着变化（log 从HovRøn和Christiansø孵化的早期到晚期，白蛋白和蛋白质显着下降，这反映了体重下降的长期支持。在Christiansø羽绒被上进行的非靶向代谢组学显示，存在8,433种血浆代谢物。其中3,179种代谢物发生了显着变化（log从早期孵育到晚期孵育的₂倍变化≥1，p≤0.05）。例如，较小的肽和维生素B ₂（核黄素）显着下调，而11-脱氧皮质酮和棕榈酰肉碱显着上调。这些结果表明，在孵化过程中包括禁食在内的累积压力会影响绒毛的生化特征和能量代谢，这对于波罗的海的克里斯蒂安索殖民地可能最为明显。这加剧了全球变暖导致温度升高和食物网变化的事件，最终加速了体重的减轻。未来的研究应检查身体状况，温度和生殖结果之间的关系，并包括绘制食物网污染物，能量和营养成分的图，以更好地了解，管理和保护人口。