The uropygial gland is an exocrine gland located above the tail of birds that produces a diverse range of biochemicals. It has been hypothesized to be involved in chemical protection, water-proofing and maintenance of plumage brightness. Although these not necessarily mutually exclusive functions have received some empirical support, there has been little empirical research on the function of water-proofing. Here we analyzed data for 229 individual eiders (Somateria mollissima) collected by Danish hunters during 2016‒2018. The Eider is a sea-duck that spends almost its entire life in sea water emphasizing water-proofing of the plumage. The size of the uropygial gland increased with body mass in males, but not in females, and it increased with age. The size of the uropygial gland decreased during winter. Eiders with small uropygial glands grew their feathers at a fast rate. Eiders with large wing areas had large uropygial glands. These findings are consistent with large uropygial glands playing a role in water-proofing during molt and foraging, but also that uropygial glands may play a role in chemical defense.

中文翻译：

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绒毛腺在绒毛中的功能（Somateria mollissima）

尿py腺是位于禽类尾巴上方的外分泌腺，可产生多种生物化学物质。据推测它涉及化学保护，防水和维持羽毛亮度。尽管这些不一定互斥的功能已经获得了一些经验支持，但是关于防水功能的经验研究却很少。在这里，我们分析了2016-2018年期间丹麦猎人收集的229羽绒鸭（Somateria mollissima）的数据。鸭绒鸭是一只海鸭，几乎一生都在海水中度过，强调羽毛的防水性。尿道腺的大小在男性中随体重增加而增加，而在女性中则不随年龄增长。冬季，尿道腺的大小减少。带有小尿道腺的绒毛以很快的速度生长。翅大的绒鸭有较大的尿道腺。这些发现与大型尿py腺在蜕皮和觅食过程中起到防水作用是一致的，而且尿g腺可能在化学防御中起作用。