Noh Hee-Jin, Gloag Ros, Leitão Ana V, Langmore Naomi E
Research School of Biology, Australian National University, Canberra ACT 0200, Australia.
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia.
Curr Zool. 2021 Jul 10;67(6):665-674. doi: 10.1093/cz/zoab056. eCollection 2021 Dec.
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) and its primary host, the large-billed gerygone , 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.
鸟类巢寄生者与其宿主之间的协同进化相互作用，常常导致宿主基于视觉线索进化出对寄生者卵或雏鸟的辨别与排斥能力，以及巢寄生者进化出对宿主卵或雏鸟的视觉拟态。宿主也可能基于声音线索来排斥巢寄生雏鸟，这反过来会促使巢寄生雏鸟进化出对宿主乞食叫声的拟态。在利用多种具有不同乞食叫声宿主的杜鹃中，叫声结构可能具有可塑性，使雏鸟能够改变叫声以匹配不同宿主的叫声，或者是固定不变的，在这种情况下，我们预计会出现不完美的拟态，或者该物种分化为特定宿主的谱系。在我们对小铜鹃（LBC）及其主要宿主大嘴噪刺莺的研究中，我们测试了：（1）宿主是否利用雏鸟叫声作为辨别杜鹃雏鸟的线索；（2）杜鹃雏鸟在整个雏鸟期是否模仿宿主的乞食叫声；（3）杜鹃的乞食叫声是否具有可塑性，从而便于模仿不同宿主的叫声。我们发现，小铜鹃的乞食叫声在孵化后不久（此时宿主通常会进行排斥）与它们的噪刺莺宿主最为相似，但随着杜鹃雏鸟长大，相似度会降低。乞食叫声结构可能被宿主用作排斥的线索，这些结果与噪刺莺的防御机制促使杜鹃雏鸟进化出特定年龄的声音拟态相一致。我们没有发现小铜鹃乞食叫声具有可塑性的证据。
