梅峰地區藪鳥重唱行為研究

Abstract

第一章 截至目前為止，針對鳥類鳴唱行為的研究多半以溫帶鳥種為對象，對於許多在熱帶及亞熱帶地區較為常見的現象，例如雌、雄鳥之間的重唱，卻是所知有限。藪鳥 (Liocichla steerii)屬於台灣特有種，雌雄鳥間會發出一唱一答的重唱聲。本實驗於2004年三月至八月間，在全台灣13個樣區收錄藪鳥的鳴唱聲，所有樣區皆有錄得重唱聲，證實重唱在全島藪鳥族群中乃是普遍可見的現象。再針對梅峰地區族群收錄特定繁殖對鳴唱聲，詳盡描述其鳴唱以利後續探討重唱功能。結果證實藪鳥的重唱，是由母鳥以多音節的應答聲，接唱在公鳥二到四音節的鳴唱聲之後而形成。根據24對藪鳥的多次錄音記錄，90%以上的公鳥有二到三種的鳴唱聲，然而母鳥並未偏好回應其配偶的特定歌曲型，表示母鳥回應與否並未受公鳥歌曲型的影響，因而證實藪鳥重唱雖然由公鳥發起，然而重唱的形成主要取決於母鳥的決定。另外，依據公鳥最常使用的歌曲型A所做的判別分析，有80%的鳴唱聲被正確地歸到發出鳴唱的個體，但母鳥的應答聲僅57%被正確地判別，表示公鳥的鳴唱聲有明顯個體差異，而母鳥間個體差異較少。此現象亦符合藪鳥重唱的特性，明顯的鳴唱聲差異可能有利母鳥在灌叢間，依據聲音辨識其配偶進而予以回應。 第二章 多的鳥類，其成對的配偶會以輪替或些許重疊的方式發出具有協調性的鳴唱聲，稱之為重唱。雖然曾有許多假說被提出來試圖解釋鳥類重唱的目的，但重唱鳥種及其重唱形式的多樣性，加上某些鳥種的重唱具有兩種以上的功能，使得科學家對此一行為的了解仍相當有限。於2004年四月初至八月期間，於南投縣梅峰山地實驗農場，進行不同繁殖對的領域描繪，並在不同的繁殖階段收錄其鳴唱聲，另外，以陌生的雄鳥獨唱與雌雄重唱對藪鳥繁殖對進行回播，以探討藪鳥重唱是否符合合作防衛領域假說。研究結果顯示，相較於自然狀態下，雌鳥在回播時明顯提高其回應比例，展示更多的重唱，顯示母鳥重唱與領域的防守相關。此外，雌鳥回應其配偶而形成重唱的意願，並未因同性入侵者的存在而改變，顯示母鳥參與重唱並未針對同性，此一結果亦符合合作防衛領域。而繁殖對的領域大小，與母鳥回應配偶鳴唱的比例呈顯著正相關，亦支持重唱與防衛領域相關的假設。另外，除了母鳥回應時間在非受精期內明顯較短外，在母鳥的非受精期與可受精期間，公鳥鳴唱頻率、母鳥回應比例、母鳥反應時間的穩定性及母鳥應答聲的音節數並無差異。

Chapter One: Studies on bird vocalizations have been focused in temperate region instead of tropics/subtropics. Duetting behavior, a more common phenomenon in tropics/subtropics, remains poorly understood, in part due to limited number of species studied. Steere’s liocichlas (Liocichla steerii) which perform duets are endemic to Taiwan. I investigated their duetting behavior, particularly focused at Meifeng Highlands Experiment Farm of National Taiwan University, in Taiwan from March to August 2004. Based on the recordings from 13 sites around the island, duets were recorded in every site, suggesting that duetting is a widespread behavior in this species. I confirmed that liocichlas form a simple male-led antiphonal duet with which males sing a 2-4 syllable song first, sometimes followed by a distinct multi-syllable female call. Each individual male has more than one song type in it repertoire. I analyzed the female answer rate to three common song types shared among males and found no difference, which indicated that even though the male leads a duet, but the decision to form a duet is from the female. A discriminate function analysis showed that 80% of the male songs could be assigned correctly to individual, however, only 57% of the female calls could be accurately assigned. This is consistent with the result that females form duets by answering their mate’s song and individual-specific male song may facilitate females to recognize and answer correctly. Chapter Two: Some paired birds coordinate their songs by alternating or overlapping notes to produce joint acoustic displays called duets. Duetting species are diverse not only taxonomically but also in their form of duets. More than one function was found in duet of some species, so until now this behavior is still a poorly understood phenomenon despite several hypotheses as to its function. I conducted territory mapping, song recordings across breeding cycle and playback experiments using recordings of both male solo and duet songs obtained from unfamiliar pairs to investigate the function of duetting, especially with joint territory defense hypothesis, in Steere’s liocichlas (Liocichla steerii) at Meifeng Highlands Experiment Farm, Taiwan. Male song and female answer rate significantly increased in response to playback of either duet or male solo song. However, we found no difference in either male or female song behavior between solo and duet playback treatments. Because females responded equally strongly to playbacks with and without a female song component our experiment provided no evidence that duetting functions in the context of same-sex territory defense but rather as a cooperative joint territory defense. The territory size was positively correlated with the answer rate of the female territory owner, further suggested that duet was associated with territory defense. In addition, except for the shorter female reaction time to form duet when they were not fertile, male song rate, female answer rate, female duet consistency and number of syllable in female calls had no significant difference between the fertile and non-fertile stage.