Abstract

We studied the home ranges and core areas of a native population of Crested Serpent-eagles in southern Taiwan by radio-tracking from November 2005 to May 2007. 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 4.52 km2 and 1.46 km2 based on the 95% fixed kernel (FK) method, respectively. Mean core areas for males and females were 1.16 km2 and 0.36 km2 based on the estimation by the Area Independent Method (AIM) and 0.64 km2 and 0.20 km2 based on the 50% FK method, respectively. Mean fixed kernel home ranges of males were 3.1 times greater than those of females, and AIM core areas of males were 3.2 times greater than those of females. All of the individuals exhibited core area overlap, especially in the case of male to male core areas. Male to male, male to female and female to female average AIM core area overlap was 37.0%, 14.9% and 1.9%, respectively with these differences all being statistically significant. Therefore, at the level of AIM core area overlap, core areas of females were smaller, and female to female relationships showed considerably more range exclusivity than those of male to female and male to male. In contrast, male core areas were more regularly shared with other male or female individuals. Since radio-tracked females were 18% heavier than radio-tracked males, we discuss how the differences in spacing pattern may be caused by female dominance.

中文摘要

本研究於2005年至2007年間利用無線電追蹤技術，針對臺灣南部不同性別與年齡的大冠鷲，進行活動範圍與核心區域的空間利用研究。採用最小多邊形（minimum convex polygon）法，計算8隻雄鳥和6隻雌鳥的平均活動範圍分別為16.65 km2 和 6.93 km2；採用固定核區域法（95% fixed kernel method）則分別為 4.52 km2 和 1.46 km2。所有個體的活動範圍經獨立區域法（Area Independent Method）驗證空間利用機率差異，證實存在客觀密集利用的核心區域，雄鳥和雌鳥此客觀利用的核心區域平均面積分別為1.16 km2 和 0.36 km2，大於主觀以50% fixed kernel area定義的0.64 km2和0.20 km2。以固定核區域法計算的雄鳥平均活動範圍是雌鳥的3.1倍大，以獨立區域法獲得的雄鳥核心區域是雌鳥的3.2倍大。所有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呈現不同程度分享。雌性個體間、雌性與雄性個體間、以及雄性個體間三個組合的核心區域面積重疊比例的平均分別為1.9%、14.9% 和37.0%，相互呈現顯著差異。相較於雄鳥對雄鳥和雄鳥對雌鳥，雌鳥對雌鳥的核心區域的空間分布與利用呈現明顯的排他性。此種雄鳥的核心區域相對較大且重疊度高以及雌鳥的核心區域相對較小且共享程度低的情形，我們認為由於雌鳥的平均體重高於雄鳥約18%，此種空間利用型態的差異與雌鳥的強勢有關。

Keyword: Core area, home range, radio-tracking, space use, Spilornis cheela hoya.