影響三種共域八哥族群數量的因子：以臺北市河濱為例

Factors affecting population abundance of three sympatric mynas – case study in Riparian Zones of Taipei City

張俊怡(Chun-I Chang)

指導教授 ： 李培芬

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.02060

摘要

在生態學上，外來種意指由人為主動或間接引入，出現於其自然分布範圍以外的物種。外來種被認為是造成原生種滅絕的其中一項原因，但實際上很多外來種對於生物多樣性的威脅並沒有實驗數據的支持。另外，環境破壞與棲地流失也被認為是造成原生物種族群下降的原因之一。家八哥（Acridotheres tristis）與白尾八哥（Acridotheres javanicus）在1970年代被引入臺灣。臺灣的原生種八哥（Acridotheres cristatellus），於2000年後族群量開始大幅下滑，一般認為原生八哥數量下降是由於引入的外來種八哥與其競爭。儘管較小尺度的棲地偏好重疊暗示著三種八哥間存有競爭關係，目前仍無直接證據證明原生八哥的確是因為與外來八哥競爭才導致其數量逐漸下降。除此之外，已有研究發現土地利用類型中的草生地面積變化是最能解釋原生八哥數量變化的因子。三種八哥對於大尺度棲地的偏好不同，很可能才是解答三種八哥的族群趨勢差異之關鍵。
　　為了得知與外來八哥的競爭是否造成原生八哥的數量下降，本研究以臺北盆地為研究樣區，利用臺北市河濱鳥類調查資料進行統計分析，以回答以下兩個問題：(1) 原生八哥和外來八哥是否有不同的大尺度棲地偏好？(2) 外來八哥出現時原生八哥的數量是否受到影響？從研究結果得知，繁殖季時原生八哥較外來八哥偏好高草叢。另外也得知，外來八哥的出現對於原生八哥的數量無負向影響，甚至在繁殖季時可發現原生八哥的出現對外來八哥的數量有負向影響。
　　本研究成果推測原生八哥所需的高草棲地減少可能為其近年來數量下降的重要因素之一，而與外來八哥競爭可能較無相關。此結果將能提供已列為臺灣第二級珍貴稀有保育類動物的原生八哥之保育工作的重要參考依據。

關鍵字

外來種 ； 保育類原生種 ； 鳥類 ； 棲地破壞 ； 競爭排除

並列摘要

Invasive species threaten native biodiversity, they have been considered as one of the reasons that make native species extinct. However, there is no enough statistical evidence could prove the decreased population of native species was due to the threat from invasive species. In addition, environmental disruption and habitat loss has also been considered as one of the reasons that make the population of native species declined. In the 1970s, Acridotheres tristis and Acridotheres javanicus were introduced into Taiwan. Meanwhile, populations of the native myna species Acridotheres cristatellus continue to decline after 2000. It is generally considered that the decreasing of A. cristatellus was due to competition with the invasive mynas. However, direct evidence of competition between these mynas has not yet been recorded. Furthermore, recent research and observations suggested that large scale habitat preferences may differ between native and invasive mynas. The difference in large scale habitat requirement between these three myna species was proposed to be a crucial point to explain the different population densities between the native and invasive mynas species.
In this study, Taipei riverside was chosen as the study sites and the previous bird investigation data of Taipei riverside bird survey was used to analyze. Eventually, this study aimed to answer the following two questions: (1) Do native species and invasive species have different large scale habitat preference? (2) Will presence of invasive species impact on native species’ population? According to the results of this research, compared to invasive mynas, the native myna especially prefer grass in breeding season. Moreover, the population of native myna doesn’t decrease with the other two invasive mynas.
These results implied the decreasing of grass habitat may be an important factor to provide an explanation of the decreasing native myna population. Moreover, this study could be an important reference for the conservation work of A. cristatellus, which has been classified as an endangered species in Taiwan.

並列關鍵字

invasive species ； protected species ； habitat destruction ； competition exclusion

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