Working with what you've got: unattractive males show greater mate-guarding effort in a duetting songbird

When mates are limited, individuals should allocate resources to mating tactics that maximize fitness. In species with extra-pair paternity (EPP), males can invest in mate guarding, or, alternatively, in seeking EPP. Males should optimize fitness by adjusting investment according to their attractiveness to females, such that attractive males seek EPP, and unattractive males guard mates. This theory has received little empirical testing, leaving our understanding of the evolution of mating tactics incomplete; it is unclear how a male's relative attractiveness influences his tactics. We conducted observations and experiments on red-backed fairy-wrens (Malurus melanocephalus) to address this question. We found that older, more attractive (red–black) males sought EPP, whereas unattractive (brown) males invested in alternative tactics—physical and acoustic mate guarding. Younger red–black males used intermediate tactics. This suggests that males adopt mating tactics appropriate to their attr...当配偶资源有限时，个体应将资源分配给能最大化自身适合度的交配策略。在存在婚外父权（extra-pair paternity, EPP）的物种中，雄性可选择投入配偶守卫行为，或是转而寻求婚外父权。雄性应根据自身对雌性的吸引力调整资源投入，以此优化适合度：吸引力高的雄性会寻求婚外父权，而吸引力低的雄性则专注于配偶守卫。该理论尚未得到充分的实证检验，导致我们对交配策略演化的理解仍存在缺口，目前尚不清楚雄性的相对吸引力如何影响其交配策略选择。我们以红背细尾鹩莺（Malurus melanocephalus）为研究对象开展了观察与实验，以解答这一问题。研究结果显示，年龄更大、吸引力更强的（红黑羽色）雄性会寻求婚外父权，而吸引力较低的（棕羽色）雄性则采取替代性策略——物理守卫与声学守卫配偶。年轻的红黑羽色雄性则采用介于两者之间的中间策略。这表明雄性会采取与其吸引力相匹配的交配策略……