棕扇尾鶯與褐頭鷦鶯在農田中繁殖生態之比較

Comparison of Breeding Ecology of Zitting Cisticola (Cisticola juncidis) and Tawny-Flanked Prinia (Prinia subflava) in the Rice Paddy

棕扇尾鶯（Cisticola juncidis）與褐頭鷦鶯（Prinia subflava）均屬於雀形目（Passeriformes）鶯科（Sylviidae）的鳥類，在台灣低海拔及平原地區是很常見的鳥種，且同時繁殖於稻田中，為了解兩者間的繁殖行為與生態，及其與農業活動的關係，自2004 年2 月至2005 年5 月在台灣南部高雄地區的稻田中進行本研究，共觀察了47 個棕扇尾鶯與31 個褐頭鷦鶯繁殖巢位。棕扇尾鶯的繁殖自3 月初即已開始，較褐頭鷦鶯的繁殖略早1 個月，兩者在農田中的繁殖高峰均集中於4 月中，且巢均築於未結穗的稻苗，在植株高度的2／3 處（68.1%與67.4%）。隨著稻苗的生長，先築巢的棕扇尾鶯的巢位高度顯著的較後築巢的褐頭鷦鶯為低（49.1±8.9 cm<64.6±7.4 cm），棕扇尾鶯的巢位距田埂的平均距離也較褐頭鷦鶯為短（124.3±86.6 cm<353.4±176.3 cm）。棕扇尾鶯的巢身（6.4±0.7 cm 與7.9±0.4 cm）與巢口的直徑（4.1±1.2 cm與4.5±0.9 cm）均較褐頭鷦鶯為小。兩者的平均產卵數（3.9±0.6與3.7±0.6 個）、孵化時間（16.0±0.6 天與17.6±1.7 天）、孵化成功率（61.3 % 與65.9 %）、剛孵出的雛鳥平均體重（0.74±0.10g與0.72±0.10g）、雛鳥的生長速率（0.45±0.20g∕天與0.41±0.11g∕天）、在巢時間（13.3±0.8天與13.0±0.6天）、幼鳥離巢時的體重（6.1±2.8g 與5.7±2.4g）與每巢平均成功離巢幼鳥數（2.5±1.6隻與2.2±1.7隻）差異均不顯著。但棕扇尾鶯的繁殖成功率明顯的高於褐頭鷦鶯（62.1% >42.3%），主要為兩種鳥類繁殖時間先後的不同，受到5月初農田稻作開始收割、環境中梅雨季節的來臨並連續的降雨等重要因素，是造成較晚繁殖的褐頭鷦鶯與較早繁殖的棕扇尾鶯繁殖差異的主要原因。 Zitting Cisticola (Cisticola juncidis) and Tawny-flanked Prinia (Prinia subflava) are birds belonging to the family Sylviidae. They are commonly found in lowlands and costal plains of Taiwan, and share rice paddies as breeding habitat and have fairly similar breeding season. In order to understand their breeding ecology and effects of agricultural activities, this study was conducted in the Kaohsiung area of the southern Taiwan in February 2004 to May 2005. A total of 47 nests of Zitting Cisticola and 31 nests of Tawny-flanked Prinia were observed. The breeding season of the two species were from March to November but with the peak months in March and April for the former and in April for the latter. As compared to the Tawny-flanked Prinia, the Zitting Cisticola had significantly lower nesting sites on rice stalks (Zitting Cisticola via Tawny-flanked Prinia: 49.1±8.9cm via 64.6±7.4cm), shorter distances from banks of paddy fields (124.3±86.6cm via 353.4±176.3cm), and smaller nests (6.4±0.7cm via 7.9±0.4cm in diameters) with narrower nest mounths (4.1±1.2cm via 4.5±0.9cm in diameters). No significant difference were found for egg sizes, clutch sizes, incubation periods, hatching rates, nestling and fledgling sizes, and their growth rates and nesting periods. However, breeding success of the Zitting Cisticola was significantly higher than that of the Tawny-flanked Prinia (62.1%＞42.3%). This difference might be due to different breeding sequence of the two species in relation to the rice harvest activies and high rainfalls in the month of May.