Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada.
Section of Animal Biology, Department STEBICEF, University of Palermo, Palermo, Italy.
Sci Rep. 2018 Jul 12;8(1):10569. doi: 10.1038/s41598-018-28275-3.
Avian nest defence, which is expected to serve both antiparasite and antipredator functions, may benefit or be detrimental to birds, although selective forces that potentially operate on nest defence have not been quantified as a whole. Together with fitness values, we analysed two traits of nest defence, intensity and plasticity, in two distantly related passerine species, yellow warbler (Setophaga petechia) in North America and reed warbler (Acrocephalus scirpaceus) in Europe, both favourite host species for brood parasites. Breeders that escaped parasitism were the most vocal among reed warblers, whereas there was no specific defence phenotype that predicted prevention of parasitism in yellow warblers. Breeders that escaped nest predation were, in both species, those with the most distractive response at the first exposure to a nest-threatening event, such as the experimental predation or parasitism simulated at the nest. However, increasing defence intensity benefited yellow warblers but was detrimental to reed warblers, because intense defence responses attracted predators. Adaptiveness of nest defence was revealed by nest defence phenotypes when examined in concert with the seasonal fitness (i.e. measures of reproductive success). Results revealed selective forces favoured yellow warblers with strong defence phenotypes. Opposite forces were instead revealed among reed warblers whose favoured phenotypes were strong, yet less flexible, defenders.
鸟类的巢防御行为，预计具有抗寄生虫和抗捕食的功能，可能对鸟类有益或有害，尽管潜在作用于巢防御的选择压力尚未被全面量化。我们分析了两种巢防御特征的适应值，即强度和可塑性，这两种特征在两种亲缘关系较远的雀形目鸟类中有所体现，一种是北美的黄莺（Setophaga petechia），另一种是欧洲的芦苇莺（Acrocephalus scirpaceus），它们都是巢寄生的首选宿主物种。在芦苇莺中，逃避寄生的繁殖者叫声最响亮，而在黄莺中，没有特定的防御表型可以预测寄生的预防。在这两个物种中，逃避巢捕食的繁殖者是在第一次接触巢威胁事件（如在巢中模拟的实验性捕食或寄生）时反应最具干扰性的繁殖者。然而，在黄莺中，增加防御强度是有益的，但对芦苇莺则是有害的，因为强烈的防御反应会吸引捕食者。巢防御表型与季节性适应值（即繁殖成功率的衡量标准）一起检查时，揭示了巢防御的适应性。结果表明，选择压力有利于具有强烈防御表型的黄莺。而在芦苇莺中则揭示了相反的力量，它们所青睐的表型是强有力但缺乏灵活性的防御者。
