The Patterns Of Four Species' Singing Activities Associated With Seasonal Shift In Ta-pieh Mountains

Birds' dawn chorus is a daily period of high singing activity,which mainly occurs during the breeding season.However,despite its significance in birds' life cycle,we still do not know why birds sing at dawn.Similarly,birds' vocal behavior can change daily and seasonally.Monitoring such chorus is helpful to understand behavioral ecology,signal function,and conservation status.Acoustic recording technologies provide cost-effective methods to monitor vocally active species.The use of these technologies is rapidly growing in studies covering multiple aspects of bird ecology and behavior,including migration patterns,presence-absence surveys,nocturnal and cryptic species monitoring,and climatic impacts on populations.However,it has been rarely applied to study the singing behavior of Asian birds,especially at a large temporal scale.This thesis has employed this technology and investigated the dawn,daily and seasonal singing activity of four Asian passerines.Song Meter SM4+was used continuous,uninterrupted recording of length at least 4.5 h during daily dawn chorus(April-June 2019)at the seven sites of Yaoluoping National Nature Reserve(YNNR),located in the hinterland of Ta-pieh Mountains,and additionally acquired audio recordings at three of these sites for 5 min at 30-minute intervals throughout the day for a year(April,2019 to Mrach,2020).The four bird species Alstrom's Warbler(Phylloscopus soror),Streak-breasted Scimitar Babbler(Pomatorhinus ruficollis),Brownish-flanked Bush Warbler(Horornis fortipes),and Hwamei(Garrulax canorus),were identified by listening to each 5 min or 4.5 h audio recording and visually inspecting their spectrograms,displayed with Raven Pro 1.5.0 using a Hann window,FFT=512,overlap 50%,and frame size 100%.The results of this study are as follows:1.Based on the recording spectrograms,singing patterns of the four species were obtained.I found that the Julian date did not affect the dawn singing start time of any species.However,they were different in the singing rates during the dawn chorus,suggesting that patterns of songs are species-specific.Therefore,this specificity is related to the function of birds'songs,and it may vary even within species depending upon the time of the season.2.My data showed that Alstr(?)m's Warbler,Streak-breasted Scimitar Babbler,and Brownish-flanked Bush Warbler started singing later at the higher temperature;however,dawn singing start time of Hwamei was not affected by temperature change.Alstr(?)m's Warbler and Brownish-flanked Bush Warbler's singing rate decreased significantly with high temperatures,whereas the singing rates of the other two species were not significantly related to the temperature.I conclude that higher temperatures resulted in later onset and decreased the singing rate at dawn,therefore,bird song patterns and changes are related to seasonal changes in environmental factors.3.I found a large temporal variation in singing activity within a day and season and these differences were mainly related to the social interactions and species ecology.The daily singing pattern indicated that all the three species displayed a peak in singing activity in the morning;however,they differed in their acoustic activity during the daytime.The analyses of the annual cycle revealed that Alstr(?)m's Warbler was vocally active for five months(April-August),with higher singing activity earlier in the season.Brownish-flanked Bush Warbler remained active for six months(March-August)and showed a significant variation in singing activity over time.Streak-breasted Scimitar Babbler was found vocally active for nine months(March-November)and displayed a slight variation in singing activity among months at different sites.Different habitats further diverged such daily and seasonal patterns of the birds singing.This thesis highlights the importance of using acoustic recording technologies for ecological studies in complex sonic environments.The study of seasonal song patterns of four passerines species provides a foundation for further research into the factors that cause seasonal variation.At the same time,by linking singing activities to weather factors,this thesis further demonstrates that acoustic recording technology provides an important tool for how climate change can alter bird behavior by assessing the impact of weather on singing activities.In addition,the findings of this thesis will encourage to move from a single or few species focus to a community and soundscape focus.