“…For cuckoos, a well‐studied brood parasitic avian species, the temporal and frequency variables of male “cu‐coo” calls (Figure a) are well‐known (Lei, Zhao, Wang, Yin, & Payne, ). This call type is sufficient to provide individual information (Jung, Lee, & Yoo, ; Li, Xia, Lloyd, Li, & Zhang, ; Zsebök, Moskat, & Ban, ), which can be used to distinguish between neighbors and strangers (Moskát, Elek, Ban, Geltsch, & Hauber, ; Moskát et al, ): Male cuckoos show less aggressive response to familiar “ cu‐coo ” calls from neighbors than unfamiliar “ cu‐coo ” calls from strangers during playback experiments. Besides the characteristic and conspicuous two‐element “ cu‐coo ” calls, males can also utter a three‐element “ cu‐cu‐coo ” call (Figure b) which contains a repeat of the first element of the regular “ cu‐coo ” call (Lei et al, ; Payne, ).…”