Abstract

Coevolutionary interactions between avian brood parasites and their hosts often lead to the evolution of discrimination and rejection of parasite eggs or chicks by hosts based on visual cues, and the evolution of visual mimicry of host eggs or chicks by brood parasites. Hosts may also base rejection of brood parasite nestlings on vocal cues, which would in turn select for mimicry of host begging calls in brood parasite chicks. In cuckoos that exploit multiple hosts with different begging calls, call structure may be plastic, allowing nestlings to modify their calls to match those of their various hosts, or fixed, in which case we would predict either imperfect mimicry or divergence of the species into host-specific lineages. In our study of the little bronze-cuckoo (LBC) Chalcites minutillus and its primary host, the large-billed gerygone Gerygone magnirostris, we tested whether: (1) hosts use nestling vocalizations as a cue to discriminate cuckoo chicks; (2) cuckoo nestlings mimic the host begging calls throughout the nestling period; and (3) the cuckoo begging calls are plastic, thereby facilitating mimicry of the calls of different hosts. We found that the begging calls of LBCs are most similar to their gerygone hosts shortly after hatching (when rejection by hosts typically occurs) but become less similar as cuckoo chicks get older. Begging call structure may be used as a cue for rejection by hosts, and these results are consistent with gerygone defenses selecting for age-specific vocal mimicry in cuckoo chicks. We found no evidence that LBC begging calls were plastic.

中文翻译：

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寄生杜鹃对宿主乞求呼叫的不完美模仿：宿主拒绝雏鸟的线索？

摘要

鸟类孵化寄生虫与其宿主之间的共同进化相互作用通常导致宿主基于视觉线索对寄生虫卵或雏鸡的歧视和排斥的进化，以及孵化寄生虫对宿主卵或雏鸡的视觉模仿的进化。宿主还可能基于声音提示拒绝寄生寄生虫雏鸟，这反过来会选择模仿寄生寄生虫小鸡的寄主乞求呼叫。在利用具有不同乞求呼叫的多个宿主的布谷鸟中，呼叫结构可能是可塑性的，允许雏鸟修改它们的呼叫以匹配其各种宿主的呼叫，或者是固定的，在这种情况下，我们可以预测物种的不完美模仿或分化成宿主- 特定的血统。在我们对小青铜杜鹃 (LBC)方铅矿的研究中及其主要宿主大嘴杜鹃Gerygone magnirostris，我们测试了是否：（1）宿主使用雏鸟发声作为区分杜鹃雏鸟的线索；(2) 杜鹃雏鸟在整个雏鸟期间模仿宿​​主乞求的叫声；(3)杜鹃乞求的叫声是可塑的，便于模仿不同宿主的叫声。我们发现 LBC 的乞求呼叫在孵化后不久与它们的 gerygone 宿主最相似（通常发生宿主拒绝时），但随着杜鹃雏鸡变老而变得不那么相似。乞求呼叫结构可用作宿主拒绝的提示，这些结果与杜鹃小鸡中针对特定年龄的声音模仿的gerygone防御选择一致。我们没有发现任何证据表明 LBC 的乞讨电话是塑料的。