大冠鷲(Spilornis cheela hoya)活動範圍與棲地選擇

HOME RANGE AND HABITAT SELECTION OF CRESTED SERPENT-EAGLE (Spilornis cheela Hoya)

周大慶(Ta-ching Chou)

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/博士(2011年)

https://doi.org/10.6342/NTU.2011.03290

摘要

人類對猛禽主要的威脅包括棲地破壞、環境污染和獵殺。大冠鷲(Spilornis cheela hoya)是蛇鵰(S. cheela)這個種類中體型最大的亞種且僅分布於台灣。由於侷限於一個地區或小島上的特有物種，其存活更容易受到各種威脅影響，因此收集猛禽對棲地需求和利用的訊息，有助於增進保育管理計劃的發展和有效性。
本研究於2005年至2007年間利用無線電追蹤及地理資訊系統，針對台灣南部不同性別與年齡(成鳥和亞成鳥)的大冠鷲，進行活動範圍與核心區域的交互作用與空間利用監測。根據最小多邊形 (minimum convex polygon, MCP) 法，8隻雄鳥和6隻雌鳥的平均活動範圍計算分別為16.65 km2 和 6.93 km2；根據固定核心區域法(95% fixed kernel method, 95% FK)則分別為 4.50 km2 和 1.46 km2。所有個體的活動範圍經獨立區域法(Area Independent Method, AIM)驗證，存在客觀集中利用的核心區域，雄鳥和雌鳥的客觀核心區域平均大小分別為1.16 km2 和 0.36 km2，大於主觀以50% fixed kernel定義的雄鳥(0.64 km2)和雌鳥(0.20 km2) 核心區域面積。以固定核心區域法計算的雄鳥平均活動範圍是雌鳥的 3.2 倍大，以AIM 獲得的雄鳥核心區域是雌鳥的 2.9倍大。所有被繫放個體的活動範圍呈現高度相互重疊，甚至核心活動區域也與其他個體分享。雌性-雌性、雌性-雄性、以及雄性-雄性個體間三種組合的核心區域面積重疊的平均比例分別為1.9%、14.9%、和37.0%，兩兩之間呈現顯著差異，即雄鳥的核心區域重疊度高，雌鳥的核心區域享程度低。相較於雄鳥對雄鳥和雄鳥對雌鳥，雌鳥之間的核心區域的空間分布與利用呈現明顯的排他性，由於雌鳥的平均體重高於雄鳥18%，此種空間利用型態的差異顯然與雌鳥的強勢行為有關。
雖然不同性別個體在年度活動範圍大小呈現明顯差異，但是在乾季則只有95% FK活動範圍有顯著差異。不同年齡(成鳥、亞成鳥和幼鳥)的年度和乾季活動範圍無明顯差異，但在濕季亞成鳥的MCP活動範圍小於成鳥及幼鳥。除了亞成鳥，成鳥、幼鳥、雌鳥、雄鳥等組合，以及綜合所有個體，比較其乾季和濕季間的MCP及95% FK活動範圍沒有明顯差異。
此外，為了解在整個研究區和個別個體的活動範圍兩種層級的空間尺度下，大冠鷲對於棲地的利用是否具有選擇性，以及哪一些棲地型態是大冠鷲重要的棲地。我採用並比較距離分析(distance-based analysis, DA)和構成分析(compositional analysis, CA)兩種常用的棲地選擇分析方法在結果排序上的不同。以DA 和CA兩種方法都能證明大冠鷲在整個研究區和個別的活動範圍兩個尺度下對棲地型態有非逢機利用的現象。雖然兩種方法對棲地偏好排序在最前的 混合林和相思樹林兩類棲地順序一樣，但混合林利用比例高於相思樹林甚多。CA法除了較無法偵測出利用邊緣棲地的情況，對於部分可用棲地類型受限於在高一層級尺度的選擇下被排除時，使得CA法遺失這類棲地的訊息。不若DA法資料獲得具有不受個體活動範圍限制的優勢。
我也注意到，由研究區高密度的大冠鷲族群分布，以及能夠利用各種棲地環境，雖然有程度上差異，仍然符合島嶼症狀(insular syndrome)中的密度補償和生境擴張兩個主要現象。
由於亞洲地區相關大冠鷲定量棲地研究資料並不多，本研究所獲得大冠鷲活動範圍、重要棲地類型與特色、以及相對利用程度等資訊，可供這個物種及其他地區亞種的棲地保育或經營管理策略參考。

關鍵字

無線電追蹤 ； 活動範圍 ； 核心區域 ； 空間利用 ； 棲地選擇 ； 大冠鷲

並列摘要

The Formosan Crested Serpent-eagle (Spilornis cheela hoya) is regarded as the largest subspecies of the Serpent-eagle and endemic to Taiwan. The survival of endemic species limited to one region or on little island are especially more likely to be threatened. Quantitative researches about their demand for the use of space and habitats in this region are very limited. Gather information on the habitat requirements and utilization of a raptor species will improve the development and effectiveness of management plan for its conservation.
I studied the home range and core areas of a native population of Crested Serpent-eagles in southern Taiwan by radio-telemetry from November 2005 to May 2007. Geographic information system were used to assess size of ranging area and as well as habitat composition. Mean home range areas for eight male and six female individuals were 16.65 km2 and 6.93 km2 based on the estimation by the minimum convex polygon (MCP) method and 4.50 km2 and 1.46 km2 by the 95% fixed kernel (FK) method, respectively. Mean core areas for male and female were 1.16 km2 and 0.36 km2 based on the estimation by the AIM (Area Independent Method) and 0.64 km2 and 0.20 km2 by the 50% FK method, respectively. Mean kernel home ranges of male eagles were 3.2 times greater than those of females, and AIM core areas of males were 2.9 times greater than those of females.
All of the individuals exhibited core area overlap, especially in the case of male to male core areas. Female to female core area overlap was on average 1.9%. The same female had on average 14.9% of its core area overlapping with that of another male’s core area. Male to male average core area overlapping was 37.0%. These three combinations of core area overlap ratios were statistically significant. In general, relationships of female-female at the level of core area showed range exclusivity than female-male and male-male. Male core areas were considerably shared with the other same sex and opposite sex birds, but the core areas of female eagles were smaller and showed an extremely low level of sharing with other females. Since female eagles were 18% heavier than males, the difference in spacing pattern may be related to female dominance.
In dry season, significant differences were observed between sexes in 95% FK area, but not in MCP home range. Annual and dry season home ranges were similar between ages, but in wet season subadults had smaller MCP home range then adults and juveniles. There was no seasonal difference in the MCP home range and 95% kernel area using by the total individuals or subgroups of males, females, adults and juveniles.
Compositional analysis (CA) approach and distance-based analysis (DA) approach were adopt to test whether eagles selected particular habitats at two scales: selection of home ranges within the study site and selection of habitats within home ranges. Both DA and CA methods demonstrated that habitats used nonrandom in both study area scale and home range scale, however, only two top-ranking habitats, mixed forest and Acacia confusa forest, typically secondary forest, were the same for different habitat analysis techniques.
According to this research, Crested Serpent-eagles were sedentary to their ranging area in southern Taiwan. No distinct seasonal ranges shifting or migratory behavior was observed among banded individuals. Local population displaying with high density and exerting all types of forest habitat provide a supplement to the phenomenon of insular syndrome.
The results of this study contribute to identifying Crested Serpent-eagles’ vital attributes of home range size, habitat components, and relative proportional habitat utilization, which may probably be applied to planning habitat conservation and forest management plans for them and related species.

並列關鍵字

radio-telemetry ； home range ； core area ； space use ； habitat selection ； Spilornis cheela hoya

參考文獻

Lin, W.-H. 2005. A review of the breeding ecology of the Crested Serpent Eagle (Spilornis cheela ) in the Taipei area. Raptor Res. Taiwan 5: 31-44. [In Chinese with English summary]

Naoroji, R. K., and S. G. Monga. 1983. Observations on the crested serpent eagle (Spilornis cheela) in Rajpipla Forests - south Gujarat. J. Bombay Nat. His. Soc. 80: 273-285.

Lu, S.-H., L.-S. Hwang and K.-J. Tang. 2004. Diurnal and annual temperature variations in experimental forests of the Taiwan Forestry Research Institute. Taiwan J. For. Sci. 19: 15-25.

Wu, S.-H., C.-L. Pan, H.-L. Ku, H.-Y. Tzeng and H.-H. Wang. 2007. Diversity of Lianas in Kentign uplifted coral reef forest, Southern Taiwan. Quarterly J. of Chinese Forestry. 40: 31-42. [In Chinese]

Chang, H.-W., T.-C. Chou, G. De-Leung, C.-A. Cheng, C.-C. Chang, C.-T. Yao, L.-Y. Chuang, C.-H. Wen, Y.-C. Chou, K.-Y. Tan, and C.-C. Cheng. 2008. An improved PCR method for gender identification of eagles. Mol. Cell. Probe. 22: 184-188.