Pathogenic microorganisms select for a plethora of defensive mechanisms on their hosts. In males of some species, flashy traits might signal antimicrobial capacity and, thus, they might be favoured in scenarios of sexual selection. Antimicrobial capacity of individuals may predict reproductive success in males, and it could be adapted to changing environments. However, evidence for these associations is still scarce in females. Here, we evaluated antimicrobial capacity of spotless starling Sturnus unicolor females during the mating and nestling–provisioning phase. We did this by measuring 1) the blood plasma inhibition capacity against 12 bacterial strains (antagonistic index), 2) the constitutive innate humoral immunity (lysis and agglutination capacity, a non‐specific first barrier of protection of hosts against microbial parasites) and 3) the uropygial gland size and volume of secretion produced, relevant traits in the protection against, among others, feather‐degrading bacteria. We also measured colouration of throat and back feathers, and of leg and beak integuments. This information was collected during the pre‐laying and nestling stages to compare values from these two periods. We found an increase in the plasma antagonistic index from the pre‐laying to the nestling period, while a decrease on the plasma capacity of agglutination of foreign antigens. Both plasma antagonistic index and humoral immune response measured before breeding were positively related to future female reproductive success. In addition, the level of antimicrobial capacity was related to colouration of leg skin and beak integuments and of back feathers. These associations suggest that, similar to males, females might show through their physical appearance their capacity to fight microbial infections; information that could be evaluated by their potential partners and by female competitors.

中文翻译：

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雌性一尘不染的star鸟的抗菌能力与其体色和繁殖成功有关

病原微生物在其宿主上选择了多种防御机制。在某些物种的雄性中，浮华性状可能表明其抗菌能力，因此，在进行性选择时可能会受到青睐。个人的抗菌能力可以预测男性的生殖成功，并且可以适应不断变化的环境。但是，女性仍然缺乏这些关联的证据。在这里，我们评估了无斑点八哥S八哥的抗菌能力雌性在交配和提供雏鸟的阶段。我们通过以下方法做到这一点：1）对12种细菌菌株的血浆抑制能力（拮抗指数）； 2）先天性体液免疫（溶解和凝集能力，保护宿主抵抗微生物寄生虫的非特异性第一障碍）； 3 ）产生的尿道腺大小和分泌量，在抵御羽毛降解细菌等方面具有相关的特征。我们还测量了喉咙和背部羽毛的颜色，以及腿和喙的外皮的颜色。该信息是在预铺设和筑巢阶段收集的，以比较这两个时期的值。我们发现从预产期到雏鸟时期血浆拮抗指数增加，同时降低了外源抗原凝集的血浆能力。繁殖前测得的血浆拮抗指数和体液免疫反应均与未来女性生殖成功呈正相关。此外，抗菌能力的水平与腿部皮肤和喙皮的颜色以及后羽的颜色有关。这些关联表明，与男性相似，女性可能通过其外表表现出抵抗微生物感染的能力。他们的潜在合作伙伴和女性竞争对手可以评估的信息。抗菌能力的水平与腿部皮肤，喙皮和后羽毛的着色有关。这些关联表明，与男性相似，女性可能通过其外表表现出抵抗微生物感染的能力。他们的潜在合作伙伴和女性竞争对手可以评估的信息。抗菌能力的水平与腿部皮肤，喙皮和后羽毛的着色有关。这些关联表明，与男性相似，女性可能通过其外表表现出抵抗微生物感染的能力。他们的潜在合作伙伴和女性竞争对手可以评估的信息。