The preen gland produces oily secretion, which smeared onto a bird’s plumage improves its maintenance. The main components of the secretion are waxes, and its composition often changes during the year. The aim of this study was to determine the differences in the chemical composition of preen waxes in adult herring gulls Larus argentatus, captured in Poland in winter and in the breeding season. Preen gland secretions of herring gulls consist of monoester waxes, composed of about 29 saturated C₇–C₁₆ fatty acids and about 51 saturated C₁₁–C₂₀ alcohols. Unbranched-octanoic acid and n-hexadecanol dominated fatty acid and alcohol fractions, respectively, but 2-methyl-branched compounds were numerous in all individuals. The chemical compositions of fatty acids and alcohols differ between winter and the breeding season. In breeding gulls, 2-monomethyl-branched fatty acids were lower in content or could not be found, contrary to herring gulls in winter, where 2-monomethyl-substituted fatty acids were the second most abundant among all the fatty acids. Breeding gulls had also a higher content of n-octanoic acid and n-hexadecanol and a lower content of 2,6- and 2,8-dimethyl-substituted fatty acids than individuals caught during the winter. Differences in fatty acid composition were greater in breeding males, which incubate more often at night than breeding females. Hence, chemical changes in the preen wax composition in males may have evolved as additional nocturnal protection against mammalian predators which use olfaction to detect their prey and which are more active at night; however, this needs to be tested. Olfactory-based mate recognition in the colony also cannot be excluded at this stage of experimentation.

中文翻译：

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鲱鸥Larus argentatus的自作蜡成分的季节性变化。

唇部产生油性分泌物，将其涂抹在鸟类的羽毛上可以改善其维护。分泌物的主要成分是蜡，其成分通常在一年中发生变化。这项研究的目的是确定在冬天和繁殖季节在波兰捕获的成年鲱鸥黑鸥（Larus argentatus）的自作蜡的化学组成的差异。鲱鸥的Preen腺分泌物由单酯蜡组成，由大约29种饱和的C ₇ -C ₁₆脂肪酸和大约51种饱和的C ₁₁ -C ₂₀醇组成。非支链辛酸和n十六烷醇分别占主导地位的脂肪酸和醇馏分，但在所有个体中，2-甲基支链化合物很多。冬季和繁殖季节之间，脂肪酸和酒精的化学成分不同。在繁殖海鸥中，2-单甲基支链脂肪酸含量较低或找不到，这与冬天的鲱鸥相反，在冬天，鲱鱼中2-单甲基取代的脂肪酸在所有脂肪酸中排第二。鸥繁殖也有较高含量的ñ辛酸和ñ-十六烷醇和2,6-和2,8-二甲基取代的脂肪酸含量要低于冬季捕获的个体。育种雄性中脂肪酸组成的差异更大，与育种雌性相比，夜间孵化的频率更高。因此，雄性花椒中蜡成分的化学变化可能已经演变为对哺乳动物捕食者的夜间保护，后者利用嗅觉检测猎物，并且夜间活动更为活跃。但是，这需要进行测试。在实验的这一阶段，也不能排除菌落中基于嗅觉的伴侣识别。