“cu-coo”: Can You Recognize My Stepparents? – A Study of Host-Specific Male Call Divergence in the Common Cuckoo

Abstract

The presence of multiple host-specific races in the common cuckoo Cuculus canorus has long been recognized as an evolutionary enigma but how this genetic divergence could be maintained is still equivocal. Some recent studies supported biparental genetic contribution in maintaining the host-races, implying the necessity that they should recognize and mate assortatively with those who belong to the same host-race. One potential mechanism to accomplish this is that males may produce distinctive calls according to host-specific lineages. In order to test this hypothesis, we carried out a comparative study for male cuckoo calls recorded from three distant populations, where two populations share a same host species while the other parasitizes a different host species. Populations with similar habitat structures, maintaining comparable distance interval (ca. 150 km) between neighboring ones, were selected so as to minimize any other causes of vocal differentiation except the pattern of host use. By comparing the vocal characteristics of male cuckoos at the level of individual as well as population, we found that individual males indeed produced different calls in terms of spectral and temporal features. However, these differences disappeared when we compared the calls at the population level according to host species and geographic location. In conclusion, it seems unlikely for the cuckoos to identify the stepparent of male cuckoos based solely on the vocal characteristics, although they may be able to use this cue for individual recognition. Future studies including detailed morphological and genetic comparisons will be worthwhile to further elucidate this issue.

Identification of vocal individuality in male cuckoos using different analytical techniques

“…Studies of male cuckoos in Korea using Principal Component Analyses (PCA) and ANOVA tests revealed that individual males produce different calls in terms of spectral and temporal features and that betweenmale variation was also greater than within-individual variation (see Jung et al 2014). DFA has also been used successfully to achieve almost 100% correct rate of classifying calls to individual males, indicating very high variability in the call characteristics between different males (Zsebők et al 2017).…”

“…3. 1-day: calls from the same day; 2-day: calls from two consecutive days; 3-day: calls from days with two days interval; 4-day: calls from days with 3 days interval; 5-day: calls from days with 4 days interval expend a lot of time and energy dealing with territorial disputes with neighbors, so recognizing different individuals would be beneficial for males by reducing the need for territorial conflict (Jung et al 2014).…”

“…Two recent studies have found that inter-individual variation of the cuckoo call is greater than intra-individual variation (Jung et al 2014;Zsebők et al 2017). In these studies, the authors applied discriminant function analyses (DFA) to classify calls to individual males and found extremely high correct classification rate, almost 100%, revealing clear inter-individual difference in call features (Zsebők et al 2017).…”

The function of three main call types in common cuckoo

“…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, ).…”

“…For cuckoos, a well-studied brood parasitic avian species, the temporal and frequency variables of male "cu-coo" calls ( Figure 1a) are well-known (Lei, Zhao, Wang, Yin, & Payne, 2005). This call type is sufficient to provide individual information (Jung, Lee, & Yoo, 2014;Li, Xia, Lloyd, Li, & Zhang, 2017;Zsebök, Moskat, & Ban, 2017), which can be used to distinguish between neighbors and strangers (Moskát, Elek, Ban, Geltsch, & Hauber, 2017;Moskát et al, 2018):…”