鰲鼓濕地之小虒(Tachybaptus ruficollis) 的巢位特徵與繁殖成功率

Nest Characteristics and Breeding Success of Little Grebe (Tachybaptus ruficollis) in Aogu Wetland, Taiwan

瞭解生物與棲地的關係是制定有效保育策略與經營管理的基礎，小鸊鷉(Tachybaptus ruficollis) 是一種對水域具高度需求且普遍分布於臺灣各類濕地的水鳥，但我們對其瞭解卻相當少。本研究在鰲鼓濕地入口處及觀海樓附近的21 個池塘，蒐集2012 年及2013 年等兩個繁殖季的小鸊鷉巢位特徵及其巢成功率。研究期間共發現99 個巢，其繁殖期由4 月延續至11 月，平均窩卵數3.3 ± 1.4 顆並以4 顆卵較為常見。整體的表觀巢成功率(apparent nesting success) 為14.1%，但年間變異大。主要導致繁殖失敗的原因以天敵掠食佔46 巢為最多，其次是因為水位變動所導致淹沒或擱淺的失敗巢有27 個。多數繁殖巢(75/99) 都構築在離池塘岸堤20 m 的範圍內，各池塘所發現之繁殖巢數量與挺水植物( 蘆葦) 覆蓋度呈顯著正相關(rs = 0.43, P < 0.05)。其繁殖表現會受到窩卵數、巢高、巢位鬱蔽度及巢旁水深的影響，這可能與池塘食物資源及親鳥覓食效能，以及對抗水位變動及天敵掠食等不利繁殖因素有關。

Understanding species–habitat relationship is fundamental to effective conservation planning and management. The Little Grebe (Tachybaptus ruficollis) is a water-dependent bird species widely distributed in heterogeneous wetland ecosystems in Taiwan, but its breeding behavior and nest characteristics of life history are poorly understood. We collected characteristics of nesting sites and assessed the nesting success of Little Grebe in 21 ponds in Augo Wetland between 2012 and 2013. We found 99 nests, and the breeding season was from April to November, much longer than that of most Taiwanese breeding birds. The mean clutch size was 3.3 ± 1.4 with a modal clutch of four. The apparent nesting success was 14.1%, with high heterogeneity between the years. The leading causes of nest failure were predation (46 nests), followed by fluctuation in water levels that resulted in flooded or stranded nests (27 nests). Most nests occurred within 20 m from the embankment (75/99), and the number of nests significantly correlated with the emerged vegetation (reed) covering the ponds (rs = 0.43, P < 0.05). The breeding outcome was influenced by clutch size, nest height, nest closure, and water depth beside the nests. The food resources in ponds, the efficiency of foraging, the water level fluctuation, and the pressure from predation would reduce the nesting success.