Abstract

Disassortative mating in color-polymorphic raptors is a proposed mechanism for the maintenance of color polymorphism in populations. Selection for such a mating system may occur if there are fitness advantages of mating with a contrasting morph. In the black sparrowhawk (Accipiter melanoleucus), mixed-morph pairs may have a selective advantage because they produce offspring that have higher survival rates. Two hypotheses, which may explain the mechanism, are the “avoidance-image” and “complementarity” hypotheses. The first suggests that, within a predator’s territory, prey develop a search image for the more commonly encountered parental morph, for example, the male morph during incubation and brooding. Females of a contrasting morph to their partner would then have higher capture rates once they commence hunting in the later nestling phase. Thus, the “avoidance-image” hypothesis predicts higher provisioning rates for mixed-morph pairs. Alternatively, the “complementarity” hypothesis posits that different color morphs exploit different environmental conditions, allowing mixed-morph pairs to hunt under a wider range of conditions and predicts that food is delivered more consistently. We test these hypotheses using nest cameras to record prey delivery rates during the late nestling phase when both parents are hunting. We found support for the “complementarity” hypothesis, with mixed-morph pairs delivering food more consistently but not at a higher rate. This higher consistency in prey deliveries may explain the improved survival of the offspring of mixed-morph pairs and could, therefore, play a role in maintaining the stability of color polymorphism in this system.

中文翻译：

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对比性的父母颜色变体增加了非洲猛禽捕食的规律性

摘要

颜色多态猛禽中的杂合交配是维持种群中颜色多态性的一种拟议机制。如果通过对比变体进行配对具有适应性优势，则可以选择此类配对系统。在黑雀鹰（Accipiter melanoleucus），混合变体对可能具有选择优势，因为它们产生的后代存活率更高。可以解释其机理的两个假设是“回避形象”和“互补性”假设。第一个建议是，在捕食者的领土内，猎物会针对更常见的亲代变体（例如，在孵化和育雏期间的雄性变体）开发搜索图像。与雌性形成对比的雌性一旦在下一个雏鸟阶段开始狩猎，捕获率就会更高。因此，“避免图像”假说预测了混合形态对的更高配置率。另外，“互补性”假设认为，不同的颜色会利用不同的环境条件，允许混合形态对在更广泛的条件下狩猎，并预测食物的输送更加稳定。我们使用巢式相机测试这些假设，以记录父母双方都在狩猎的后期巢阶段的猎物输送率。我们发现支持“互补性”假说，混合形态对能够更一致地而不是更高的速度提供食物。猎物的这种较高的一致性可以解释混合形态对的后代存活率的提高，因此可以在维持该系统中颜色多态性的稳定性方面发挥作用。混合变体对可以更一致地提供食物，但速度不高。猎物的这种较高的一致性可以解释混合形态对的后代存活率的提高，因此可以在维持该系统中颜色多态性的稳定性方面发挥作用。混合形态对可以更一致地提供食物，但速度不高。猎物的这种较高的一致性可以解释混合形态对的后代存活率的提高，因此可以在维持该系统中颜色多态性的稳定性方面发挥作用。