Study On The Alarm Calls And Behavior In The Oriental Reed Warbler(Acrocephalus Orientalis) Under The Pressure Of Brood Parasitism

The alarm call of birds has the function of transmitting threatening information,and to recognize the intra-species and inter-species alarm call accurately is essential for individual's survival and reproduction.At present,researches on alarm call and information transmission under the pressure of predation in passerine birds has received much attention,however,less attention has been paid to the study of host alarm call under the pressure of brood parasitism.Does alarm call of host convey the specific information about parasite? How does host use alarm call to encode relevant information? Can the alarm information be used by inter-species individuals? These issues remain unclear.During June to July of 2016-2017,the author selected Oriental reed warbler(Acrocephalus orientalis),a common host of the common cuckoo(Cuculus canorus)as the research object,and select the Zhalong National Nature Reserve as the research area.The methods adopted in the study include specimen experiments,alarm calls recording,sound spectrum analysis,conspecific and heterospecific alarm call playback and behaviors observation.Based on the alarm calls,I tested whether Oriental reed warblers have the ability of recognize the sympatric and allopatric parasite,and I discussed and analyzed mechanism of alarm information coding and information transmission.This study found that the Oriental reed warbler attacked common cuckoo more frequently than Eurasian sparrowhawk(Accipiter nisus).They produced different alarm calls when encountering the two species.Comparing to Eurasian sparrowhawk,it produced more notes per call,lower peak frequency when facing common cuckoo.The Oriental reed warbler showed different intensity of attacking against the sympatric parasite common cuckoo and the allopatric parasite chestnut-winged cuckoo(Clamator coromandus),and produced different alarm calls.Comparing to chestnut-winged cuckoo,its alarm call contains more notes per call and higher peak frequency when facing common cuckoo.Results of conspecific alarm call playback experiment indicated that the Oriental reed warblers would return to the nest as quickly as possible and respond for a long time when hearing alarm call to common cuckoo.Results of heterospecific alarm calls playback experiment indicated that the black-browed reed warbler(Acrocephalus bistrigiceps)showed different response behavior when hearing different alarm calls of Oriental reed warbler,and its response intensity against common cuckoo was the weakest.Which showed that the Oriental reed warbler could distinguish the parasite common cuckoo from the predator sparrowhawk,and produce different alarm calls against them.The note combination types,number of notes per call and the peak frequency may play a role in the process of alarm information transmission.The Oriental reed warbler did not recognized the allopatric parasite,chestnut-winged cuckoo,as a special enemy,which indicated that recognizing parasite in host may require contact during their life history.Alarm call of Oriental reed warbler can cause different response behaviors in conspecific and heterospecific individuals,indicating receivers can make appropriate response behaviors based on the obtained alarm information.