畫眉（Garrulax canorus）鳴唱聲的地理變異

Abstract

台灣畫眉（Garrulax canorus taewanus）與大陸畫眉（G. c. canorus）為畫眉的兩個亞種，前者僅分佈於台灣，後者分佈於華中及華南地區。畫眉通常都在濃密的灌木或草叢中活動，樸素的外表，加上環境中的視覺障礙，應會降低行為展示的效率，但牠們豐富多變的鳴唱聲，卻能很容易的穿透視覺障礙傳遞出去，因此格外重要。本研究分析了20隻台灣畫眉（229段歌曲）與20隻大陸畫眉（227段歌曲）的鳴唱聲，以單音、音節、歌曲三個層次進行微地理區（族群內）及巨地理區（族群間）的比較。結果顯示，畫眉聲音的地理變異主要發生在音節層次，台灣畫眉與大陸畫眉單音種類的獨有程度沒有顯著差異，但大陸畫眉有較多獨有的音節種類，且多是單音個數較多的音節；三個錄音地點的台灣畫眉鳴唱聲各有特色，而大陸畫眉的音節種類共有率與音節語法共有率在三個錄音地點間有隨距離增加而降低的趨勢。在歌曲中，大陸畫眉的音節轉變次數較頻繁，歌曲變化較豐富，結構也較複雜，至於歌曲的頻率及長度等測量值方面，則只有最低頻率顯著低於台灣畫眉。判別分析顯示以每段歌曲的平均音節重覆次數、起始音節的單音個數、結束音節的單音個數及最低頻率分辨兩族群的鳴唱聲時，台灣畫眉的正確解析度為70.74％，而大陸畫眉的正確解析度為77.09％。推測音節為畫眉聲音傳遞的單位，同時台灣畫眉的祖先乃是大陸畫眉的少數個體，「奠基者效應」（founder effect）或冰河時期避難所（refugia）的形成，致使台灣畫眉的鳴唱聲較簡單，且大部分包含在大陸畫眉會唱的聲音內，由於台灣與大陸分離的時間還不夠長，所以兩者的鳴唱聲還保有相當程度的相似性。

Taiwan Hwamei (Garrulax canorus taewanus) and Chinese Hwamei (G c. canorus) are two of the Hwamei subspecies, the former found only in Taiwan, and the latter in central and southern Mainland China. Their drab appearance and the dense habitat they live in make their long and complex vocalization extremely important. This study compared 229 Taiwan Hwamei songs (from 20 birds) and 227 Chinese Hwamei songs (from 20 birds) at the note, syllable, songs and syntax levels both micro- and macro-geographically. The results showed that the geographic variation of Hwamei songs mainly occurred at the syllable level. Taiwan Hwamei songs from the three sampling locations differed in diverse ways, while in Chinese Hwamei songs, there was a fair amount of common syllables and syntax between sampling locations, but the extent of sharing decreased with distance. Chinese Hwamei songs were more complex than Taiwan Hwamei songs, containing significantly more syllable types, more ways of syllable changes, larger syntax combinations, and less number of syllable repeats per song. Most syllable types, ways of syllable changes, and syntax patterns in Taiwan Hwamei songs were also present in Chinese Hwamei songs, but not vice versa. This phenomenon could be a result of the founder effect or refugia. Because Taiwan has not been isolated from China for very long, the songs of these two Hwamei subspecies still have some similarities.