都市噪音對於白頭翁 (Pycnonotus sinensis)鳴聲的影響

Abstract

都市地區的擴張改變了生物居住的環境，野生動物必須面對強烈地人為選汰壓力，才能成功生活在都市地區。本研究在2008年三月到六月於台北市區以及台北縣的深坑鎮錄取了71隻白頭翁(Pycnonotus sinensis)的領域宣示鳴聲，並測量每段鳴唱之主要頻率、最高頻率、最低頻率、頻寬及持續時間等特徵以及當時低頻噪音的音量，以瞭解鳥類如何改變聲音溝通模式，以因應人為產生之低頻噪音。結果顯示，白頭翁領域宣示鳴聲的最低頻率會隨著低頻噪音的音量增加而提升(multiple linear regression, b=942.46, t=2.89, P=0.0052)，且此趨勢在台北市區與深坑鎮間並無顯著差異(t=0.397, P>0.05)。同時在主要頻率、最高頻率以及頻寬上則存在空間結構 (Moran’s I correlogram, P<0.05)，但在最低頻率上並無空間結構的存在(Moran’s I correlogram, P>0.05)。然而最低頻率與背景噪音的空間結構相似，且最低頻率的殘差也沒有空間結構(Moran’s I correlogram, P<0.05)，代表最低頻率與背景噪音音量有緊密的關係。本實驗結果顯示都市地區的白頭翁會改變鳴唱之最低頻率的方式來抵抗低頻噪音的遮蔽效應，其機制可能來自於鳴唱行為的可塑性，且與鳴聲的學習過程應無直接的關係。

Urban areas have sprawled recently, accompanied by dramatic alteration of abiotic and biotic environments. Therefore, to live in urban areas, wildlife must adjust their behavior to adapt to anthropogenic selection pressure. To reveal how birds modulate their vocal communication to accommodate noisy urban environment, advertising songs of 71 Chinese bulbuls (Pycnonotus sinensis) were recorded in two urbanized areas: Taipei City (TP) and Shenkeng Township (SK) of the Taipei County in Taiwan, during March to June, 2008. Sound characteristics, such as the peak frequency, maximum frequency, minimum frequency, delta frequency, and time span of each song were measured. The results showed that the minimum frequency of songs in Chinese bulbuls increased with the background noise level (multiple linear regression, b= 942.46, t= 2.89, P=0.0052) and such relationship was not different between TP and SK (t1,65=0.397, P>0.05). In addition, I found that the peak frequency, maximum and delta frequency were spatially structured (Moran’s I correlogram, P<0.05), but not for the minimum frequency (Moran’s I correlogram, P>0.05). However, the spatial structures of the minimum frequency and background noise were similar in shape, and the residual minimum frequency had no spatial structure (Moran’s I correlogram, P>0.05), implying the minimum frequency was highly correlated with background noise. These results suggested that the mechanism of song adjustment against noise might be due to behavioral plasticity for Chinese bulbuls.