台北地區大冠鷲的繁殖生態綜論

A Review of the Breeding Ecology of the Crested Serpent Eagle (Spilornis cheela) in the Taipei Area

林文宏(Wen-Horn LlN)

《台灣猛禽研究》 5期 (2005/09) Pp. 33-46+48-49

https://doi.org/10.30121/RRT.200509.0003

摘要

本研究整理1992－2005年間在台北地區所調查的8個大冠鷲（Spilornis cheela）巢之繁殖生態資料。結果在窩卵數方面，8個巢全都是1卵或1雛，確定本種的正常窩卵數為1。唯一測量的卵之長寬為66.3 x 52.6mm。在巢位方面，8巢中有2個乃重複利用同一巢位，巢的長徑平均為78.2cm、短徑平均為61.2cm、厚度平均為19.2cm、高度平均為7.68m，相對高度在巢數高度的75%處（N=4）。拆解1個鷹巢結果計有426根巢枝，最長者為157cm，平均為22.8cm，長度介於10－20cm的巢枝最多，占了41.5%，巢枝的長度總和約為100m，巢的乾重約為2.5kg。巢樹平均高度為10.3m（N=4），7巢樹的共同特色是具有濃密的附生植物，成為巢的基座並提供良好掩蔽。7個巢位中有6個位於非常接近人類環境（小於100m）的次生林，僅有1個在原始林。經推估繁殖時程，得知產卵日期為3月初至4月下旬、孵化日期為4月中旬至5月下旬、幼鳥離巢於7月中旬至8月上旬，離巢時的日齡為70－80天。自2個巢的90比食物記錄得知蛇類最多，佔72.2%，蜥蜴次之佔15.5%，青蛇（Cyclophiops major）是最重要的單一食物，佔了61.1%。8個巢中，有6個繁殖成功、2個失敗，整體的繁殖成功率為75%。低窩卵數與高成功率顯示大冠鷲為K策略物種。在原始森林的巢繁殖失敗可能肇因於野生動物的掠食，而鄰近人類環境的大冠鷲的高繁殖成功率其部分原因可能是掠食者甚少。

關鍵字

大冠鷲 ； 繁殖 ； 巢 ； 窩卵數

並列摘要

During 1992 to 2005, I observed 8 nests of the Crested Serpent Eagle (Spilornis cheela) in Taipei County, northern Taiwan. Herein some results of its breeding ecology are presented. All 8 broods had only 1 egg or 1 chick, verifying that the normal clutch size is 1. The only egg measured was 66.3 x 52.6 mm in length and width. Among the 8 nests, 2 were reused in different years. The average nest dimensions were 78.2 cm in length, 61.2 cm in width, and 19.2 cm in thickness (n=4). The relative height of the nest was 75% of the nest tree height (the average nest tree height was 10.3 m), and the actual height of the nest was 7.68 m (n=4). One nest was disassembled, and it was found to be composed of 426 twigs. The longest twig was 157 cm, and the average length was 22.5 cm. Twigs of 10-20 cm comprised the greatest proportion at 41.5%. The combined total length of all twigs was about 100 m. The dry weight of the nest was 2.5 kg. One characteristic common to all 7 nest trees observed was the high density of epiphytic plants. These epiphytes provided both good support of the nest and good camouflage. Six of the 7 nest sites were located in secondary forests very near places with human activities (Less than 100 m). Only one nest was located in a primary natural forest far from human activities. The estimated egg-laying period was from early March to mid-April. Eggs hatched from mid-April to late May. Eaglets fledged in mid-June to early August when they were 70-80 days old. By analyzing 90 food records from 2 nests, snakes were the most-frequent prey comprising 72.2% of prey items, followed by lizards at 15.5%. The smooth green snake (Cyclophiops major) was the most important prey species, comprising 61.1% of the prey items. Six of the 8 nests succeeded, while the other 2 failed. The overall breeding success rate was 75%. The low clutch size and high breeding success rate in nests near human environments is probably because of a much-lower risk of predation.

並列關鍵字

CrestedSerpent Eagle ； Spilornis cheela ； breeding ； nest ； clutch size