Acoustic Mimicry of Begging Calls and Its Geographical Differentiation in Nestling Common Cuckoos Toward Oriental Reed Warblers

In brood‐parasitism systems, geographical variations have been documented during nest defense and the egg stage, but research on host–parasitic nestling interactions is limited, especially within the same species. The begging calls of 5–6‐day‐old nestlings of the common cuckoo ( Cuculus canorus ) and its primary host, the oriental reed warbler ( Acrocephalus orientalis ), were recorded in China (Baiyangdian, Yongnianwa, and Zhalong), and acoustic parameters were analyzed. We found marked geographical variation in acoustic mimicry: Yongnianwa cuckoos exhibited the highest mimicry precision, Zhalong cuckoos the lowest. A dual strategy of conservative mimicry of high‐frequency spectral components and adaptive mimicry of low‐frequency spectral components was evident. Mahalanobis distance calculations confirmed geographical differentiation: compared to non‐local hosts, Baiyangdian/Yongnianwa cuckoos had higher acoustic similarity to local hosts, whereas Zhalong cuckoos did not. Begging call mimicry in cuckoos is a geographically structured trait; environmental drivers of this variation should be identified.