臺灣高海拔混種鳥群之組成結構與環境因子的關係

Mixed-species bird flock structure and its relationship with environmental factors in high elevation areas of Taiwan

廖俊傑(Chun-Chieh Liao)

指導教授 ： 丁宗蘇

共同指導教授 ： 陳炤杰(Chao-Chieh Chen)

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/碩士(2015年)

https://doi.org/10.6342/NTU201600360

摘要

兩種以上的鳥類一起移動及覓食的現象即稱為混種鳥群。混群的形成可能與增加覓食效率及降低被天敵捕食的風險有關。本研究調查台灣中部合歡山及塔塔加兩處高海拔地區混群的組成結構，並進一步探討環境因子對混群的影響。在2013年九月至2014年十二月間於兩研究地區選取箭竹草原、二葉松林、鐵杉林、雲杉林及冷杉林等不同植群類型樣區，以穿越線調查法觀察混群。記錄各混群中的參與鳥種、個體數量及海拔位置，並判定核心種。此外，也以定點計數法進行當地鳥類群聚調查，且在各植群樣區中放置溫度監測器進行溫度資料取樣。研究期間共記錄24種鳥類及1種哺乳類參與混群，混群組成平均3.9±1.6種、26.3±21.9隻(n=129)，混群中的鳥種數與個體數呈顯著正相關。高海拔混群主要由食蟲性鳥類組成，混群中食蟲性鳥類的混群傾向顯著高於植食性鳥類，且覓食區位相近的鳥種較常伴隨出現。高海拔地區的混群大致可分為樹冠層及灌木層混群兩大類，其中火冠戴菊(Regulus goodfellowi)是樹冠層混群中最常見的核心種；紋翼畫眉(Actinodura morrisoniana)則是灌木層混群中主要的核心種。各棲地中的優勢鳥種較可能擔任混群的核心種，且多數核心種在混群時的覓食區位寬度會變大。此外，植群的高度及枝葉垂直結構也會影響混群的組成，在高度較低的二葉松林中，樹冠層與灌木層鳥種較容易一起組成複合混群，也間接增加混群的參與鳥種數。參與混群的個體數有隨著海拔上升而下降的趨勢。高海拔地區的混群主要出現在非繁殖季，且鳥類的混群傾向具有明顯的季節性變化，而混群的群數及鳥種參與率也會隨氣溫下降而顯著升高。綜合上述，環境因子決定鳥種的分布及密度，進而影響混群的參與鳥種數、個體數量、擔任角色、混群傾向及混群頻度；植群內部的枝葉垂直結構也會影響鳥種的分布及覓食層次，進而影響混群的參與鳥種。而且，增加覓食效率可能是台灣高海拔地區鳥類組成混群的主要目的，高海拔地區在寒冷冬季食物較為缺乏，數種鳥類藉由混群覓食以克服食物短缺的壓力。

關鍵字

混群 ； 核心種 ； 火冠戴菊 ； 針葉林 ； 生態同功群

並列摘要

Mixed-species bird flock (MSF) is a phenomenon of two or more bird species moving together in same direction while foraging and might benefit participants by improving foraging efficiency or reducing risk of predation. I investigated the effects of environmental factors on structure of MSFs in high-elevation areas in Hehuanshan and Tataka of central Taiwan, from September, 2013 to December, 2014. Five different vegetation types were selected: Yushan Cane steppe (Yushania niitakayamensis), Taiwan Red Pine forest (Pinus taiwanesis), Taiwan Hemlock forest (Tsuga chinensis), Taiwan Spruce forest (Picea morrisonicola) and Taiwan White Fir forest (Abies kawakamii). Every month, I spent at least 5 hours in each vegetation type recording MSFs by line transect method. When encountering an MSF, I enumerated the number of each participating species and designated the nuclear species. I also surveyed local bird communities by point counts method at the same study plots. Air temperature was recorded by a pendant temperature data logger located in each vegetation type. Twenty-four bird species and a mammal species participated in the MSFs, with averages of 3.9±1.6 species and 26.3±21.9 individuals per flock (n=129). The number of species in MSFs positively correlated with flock size. Insectivores dominated the MSFs and mostly had a significantly higher flocking propensity than herbivores. Birds with similar foraging niches tended to flock together. Species composition of MSFs can be divided into two major types: canopy flock and understory flock. Flamecrest (Regulus goodfellowi) and Taiwan Barwing (Actinodura morrisoniana) were the most common nuclear species in canopy and understory flocks, respectively. Local dominant species were more likely to be the nuclear species in the MSFs. Most of nuclear species expanded their foraging niches in MSFs. Moreover, canopy height and vertical foliage structure of vegetation had strong influence on species composition of MSFs. Canopy and understory flocks usually came to form a ”mega flock” in Taiwan Red Pine forest that has a relatively lower canopy height. Flock size decreased with increasing elevation. Most of the flocks were recorded in non-breeding season, and flocking propensity varied with season accordingly. The number of MSFs and species participation rate increased with decreasing temperature. To sum up, the formation of MSFs in high elevation areas of Taiwan was strongly influenced by environmental condition. Environmental factors determine the distribution and abundance of birds, which further influence species composition, flock size, role of species, flocking propensity and flocking frequency. Vertical foliage structure of vegetation also affects distribution and foraging level of bird species, which in turn controls formation of MSFs. Improving foraging efficiency should be the main reason of forming MSFs in high elevation areas of Taiwan. With fewer food resources available in winters, several bird species flock and forage together to overcome the food limitation.

並列關鍵字

mixed-species flock ； nuclear species ； Flamecrest ； conifer forest ； ecological guild

參考文獻

陳炤杰、周蓮香。1999。福山試驗林森林鳥類之食性觀察。台灣林業科學 14: 275-287。

黃可言。2011。鳥類物種豐富度與初級生產力在中臺灣海拔梯度上的關係。國立台灣大學森林環境暨資源學研究所碩士論文。

廖煥彰。2006。塔塔加地區不同植群演替階段之鳥類群聚研究。國立台灣大學森林環境暨資源學研究所碩士論文。

羅柳墀。1987。溪頭地區藪鳥的生態學研究。國立台灣師範大學生物研究所碩士論文。

Alatalo, R. V. 1981. Interspecific competition in tits Parus spp. and the Goldcrest Regulus regulus: foraging shifts in multispecific flocks. Oikos, 37: 335-344.