| Nestlings of avian brood parasites can avoid being recognized by their hosts by begging calls simulation,which can promote the feeding of host parents.Common cuckoo(Cuculus canorus),as a typical obligated brood parasite,can lay eggs in more than 100 species of birds.In this study,we want to test whether the nestlings of Common cuckoo will adjust their begging calls in different hosts,and if this change can effectively improve the feeding frequency of the hosts.The rapid begging calls of parasitic nestlings were often considered as super-normal stimulation signals.At the same time,some studies have suggested that the parasitic nestlings need to adjust the strategy of begging calls to match the host's parent-chick communication system.In this study,we choose common cuckoo,which bred in reed wetland of Liaohekou Nature Reserve,as our study object.The cuckoo mainly parasitized on oriental reed warbler(Acrocephalus orientalis)and occasionally parasitized in the nest of reed parrotbill(Paradoxornis heudei).In this study,we used the transfer experiment of cuckoo nestlings,to record the begging calls of common cuckoo in the nest of oriental reed warblers and reed parrotbills,respectively.Furthermore,we investigated the effect of the difference of begging calls of cuckoos on feeding frequency of different hosts through playback experiment.The results showed that the begging calls of cuckoo nestlings changed in different developmental stages.There was no significant difference on the begging calls between the stages of 4-5 days and 8-9 days.However,the begging calls changed significantly in the late nestling stage(12-13 days old),as increased in the maximum frequency,peak frequency,number of syllables and call rate.Furthermore,we compared the begging calls of cuckoo nestlings and their hosts during the medium nestling stage(8-9 days old)and found there was no complete simulation between the cuckoos and their hosts(i.e.,the begging calls of Common cuckoo is different from that of its original host,the oriental reed warbler).However,in the new host nests of parrotbills,the begging calls of cuckoo chicks tends to switch to the corresponding host's begging call characteristics of the parrotbills.For example,there was no significant difference between the common cuckoo and reed parrotbill in the minimum frequency when raised in the reed parrotbill nests,while it was significant difference from that of the original hosts,oriental reed warblers.The begging calls playback shows that the feeding rate of oriental reed warbler was significantly higher than that of the control when the begging call of cuckoos and the warbler chicks.However,there was no significant difference in the feeding frequency between cuckoos raised in different hosts and between cuckoos and warblers.However,there was no significant effect on the feeding frequency of reed parrotbill when playback the begging calls of cuckoos and parrotbills.In summary,our results showed that the begging calls of cuckoo were not completely simulated with the host,however,there was some changes in different host nests,which tended to be closer to the call characteristics of their host.Furthermore,the playback experiment indicated that the response of the two hosts to the begging calls of cuckoo nestlings was different: two kinds of cuckoo calls hosted in either hosts could promote the host parental provisioning of oriental reed warbler,but the reed parrotbill was not sensitive to the change of cuckoo calls,which is not consistent with the conclusion that the cuckoo nestlings have a tendency to adjust their calls in the nests of reed parrotbill.in addition,our study also indicate that the cuckoo nestlings may adjust their call strategies continuously through the "trial and error" when the normal calls have no good stimulating effect on the host parental rearing.In future,we recommend to conduct further study on the adjustment strategy of begging call characteristics under different host environment. |
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