Wang Jiaojiao, Yang Canchao
Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou, 571158, China.
Curr Zool. 2020 Dec;66(6):649-655. doi: 10.1093/cz/zoaa021. Epub 2020 May 16.
The selective pressure exerted by avian brood parasites forces their hosts to evolve specific defense strategies. When subject to brood parasite attack, avian hosts will often emit alarm calls. To date, few studies have examined whether and how host responses to different alarm calls indicative of different enemies vary with the host's breeding stage. We carried out alarm call playback experiments during both the egg and nestling stages of the oriental reed warbler , a host of the common cuckoo . The playback exemplars were selected from recorded alarm calls of the warbler to the presence of common cuckoos, sparrowhawks , and oriental turtle doves , which represented brood parasite, predator, and harmless control, respectively. The results showed that the oriental reed warblers did not discriminate alarm calls issued to different intruder types, but the intensity of the response was significantly higher in the nestling stage than in the egg stage. Attack behavior related to sparrowhawk alarm calls was absent in the egg stage, but aggressive behavior increased dramatically and exceeded the attack frequency in response to the cuckoo alarm call in the nestling stage, implying a shift in the tradeoff between the parents' own survival and the loss of offspring. Alarm calls attracted a larger number of conspecifics than members of other species. In general, the oriental reed warbler had consistently stronger responses to different alarm calls in the nestling stage than in the egg stage, supporting the offspring value hypothesis.
鸟类巢寄生所施加的选择压力迫使它们的宿主进化出特定的防御策略。当遭受巢寄生攻击时，鸟类宿主通常会发出警报叫声。迄今为止，很少有研究探讨宿主对指示不同敌人的不同警报叫声的反应是否以及如何随宿主的繁殖阶段而变化。我们在东方大苇莺（一种杜鹃的宿主）的卵期和雏鸟期都进行了警报叫声回放实验。回放样本是从该莺对杜鹃、雀鹰和东方斑鸠出现的记录警报叫声中挑选出来的，它们分别代表巢寄生者、捕食者和无害对照。结果表明，东方大苇莺无法区分针对不同入侵者类型发出的警报叫声，但雏鸟期的反应强度明显高于卵期。卵期不存在与雀鹰警报叫声相关的攻击行为，但在雏鸟期，攻击性行为急剧增加，超过了对杜鹃警报叫声的攻击频率，这意味着亲鸟自身生存与后代损失之间的权衡发生了转变。警报叫声吸引的同种个体比其他物种的个体更多。总体而言，东方大苇莺在雏鸟期对不同警报叫声的反应始终比卵期更强，这支持了后代价值假说。
