ABSTRACT Capsule: Despite its population increase, the White-tailed Eagle Haliaeetus albicilla has not become food-limited, and does not pose a serious threat to birds of conservation concern in the region east of the Baltic Sea. Aims: We aimed to test variations in the main prey groups and dietary niche breadth of White-tailed Eagles through the years and along an environmental gradient as well as to evaluate the extent of predation on bird species of conservation concern. Methods: Prey remains were collected during nestling ringing from successful nests located in Lithuania. Results: The frequency of the prey groups varied along an environmental gradient, with a general pattern of increasing avian prey consumed by pairs breeding in areas with less abundant aquatic habitats. The frequency of alternative prey (i.e. terrestrial birds, mammals) and dietary niche breadth did not increase between 2005 and 2018 and during which time the White-tailed Eagle population nearly doubled. Instead, the occurrence of Northern Pike Esox lucius remains, which was the most frequent single prey species, increased throughout the study period. Bird species of conservation concern constituted only a small fraction of all the prey identified. Conclusions: The White-tailed Eagle has not become more dependent on alternative prey despite its population increase.

中文翻译：

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猎物遗骸揭示的白尾鹰 Haliaeetus albicilla 繁殖饮食的时空变化

摘要胶囊：尽管白尾鹰 Haliaeetus albicilla 的种群数量增加，但它并没有成为食物限制，并且不会对波罗的海以东地区受保护的鸟类构成严重威胁。目的：我们旨在测试多年来和环境梯度上白尾鹰主要猎物群体和饮食生态位宽度的变化，并评估捕食保护关注的鸟类的程度。方法：在立陶宛的成功巢穴中，在雏鸟鸣响期间收集猎物遗骸。结果：猎物群体的频率随环境梯度而变化，总体模式是在水生栖息地较少的地区成对繁殖所消耗的鸟类猎物增加。替代猎物的频率（即陆生鸟类，哺乳动物）和饮食生态位宽度在 2005 年至 2018 年之间没有增加，在此期间，白尾鹰种群几乎翻了一番。相反，作为最常见的单一猎物物种的北梭鱼 Esox lucius 遗骸的出现在整个研究期间有所增加。受保护的鸟类物种仅占所有已确定猎物的一小部分。结论：尽管白尾鹰数量增加，但它并没有变得更加依赖替代猎物。受保护的鸟类物种仅占所有已确定猎物的一小部分。结论：尽管白尾鹰数量增加，但它并没有变得更加依赖替代猎物。受保护的鸟类物种仅占所有已确定猎物的一小部分。结论：尽管白尾鹰数量增加，但它并没有变得更加依赖替代猎物。