鸟类迁徙对图们江下游湿地声景时间格局的影响

Effects of bird migration on the temporal patterns of the wetland soundscape in the downstream region of the Tumen River Basin of China

声景生态学是一个相对较新和快速发展的研究领域,被动声学监测技术和声学指数已经成为研究湿地鸟类和声景多样性的重要方法。本研究评价了鸟类迁徙对中国东北图们江流域下游湿地声景日、月和季节变化的影响。我们从2020年11月至2021年12月在图们江下游敬信湿地设置10个采样点,获得91,988条时长5min的有效音频,计算了声音复杂度指数(acoustic complexity index,ACI)、生物声学指数(bioacoustic index,BIO)、声音均匀度指数(acoustic evenness index,AEI)和标准化声景差异指数(normalized difference soundscape index,NDSI)以及1–11 k Hz频段的功率谱密度(power spectral density,PSD)。结果表明,声学指数对鸟类迁徙活动敏感,其中2个迁徙期声景(2–4月和10–11月)都以1–2k Hz雁类白天的叫声为主,NDSI显著降低,1–2k Hz的PSD显著升高,但雁类向北迁徙时几个声学指数变化更为敏感,有效地捕获了迁徙峰值,表明不同季节鸟类迁徙模式存在差异。非迁徙期声景由夏候鸟、蛙类和昆虫发声为主,4种声学指数和PSD随月份呈现不同的动态特征,反映了声景的多样性和复杂性,其中5–7月声景以2–11 k Hz的夏候鸟鸣唱(呈现显著高的黎明和鸣行为)和2–3 k Hz的蛙类鸣叫为主,8–9月声景以2–3 k Hz、4–5 k Hz和6–10 k Hz频段的夜间昆虫鸣叫为主,12月至次年1月仅记录到少量的鸟类发声活动。综上所述,图们江下游湿地声景呈现明显的日和月变化规律,多种声学指数联合使用可以有效地监测迁徙鸟类物候的变化,特别是追踪春季雁类向北迁徙的时间和规模。随着全球气候变暖,我们的结果强调声景监测与声学指数的应用可成为监测迁徙鸟类群落对气候变化响应的有效方法。

Aims:Bioacoustics may provide an effective method for monitoring changes in wetland bird activity and soundscape,yet phenological and seasonal patterns remain poorly understood.In this study,we examine the seasonal and diel soundscapes,as well as the utility of bioacoustics in detecting changes in songbird phenology in the downstream region of the Tumen River Basin of China.Methods:Between November 2020 and December 2021,91,988 acoustic recordings were collected at 10 sites from the Jingxin Wetland,a stopover ground for numerous migratory bird species.For each sample,we record the acoustic complexity index(ACI),bioacoustic index(BIO),acoustic evenness index(AEI),normalized difference soundscape index(NDSI)and power spectral density(PSD)values.Results:Our analysis show that seasonal shifts and bird migration have a significant effect on the composition and diversity of wetland soundscape.The 1–2 k Hz daytime vocal signals of wild geese dominated the soundscapes of two migration periods(February–April and October–November),resulting in a significant decrease in NDSI and a significant increase in PSD at 1–2 k Hz.Acoustic indices are sensitive to bird migration,but changes in bioacoustics were less abrupt in the fall,suggesting that spring recordings are better suited to indicate phenology.Summer birds and insects dominated the soundscape of non-migration period.Conclusion:We find that the soundscape of the Tumen River’s downstream wetland exhibits clear annual and diurnal rhythm.Our experiment demonstrates the use of multiple acoustic indices in conjunction can effectively monitor changes in migratory bird phenology,particularly the time and population size at which wild geese fly back north in the spring.Furthermore,we conclude that acoustic recordings,in combination with acoustic indices,may be a useful method for tracking shifts in songbird communities caused by climate change.