福山試驗林繡眼畫眉（Alcippe morrisonia）之年齡判定及族群動態學研究

Abstract

為建立繡眼畫眉年齡判別的方法，並進而瞭解福山地區繡眼畫眉（Alcippe morrisonia）族群動態，探討季節及颱風因數的影響，1994年元月至1998年10月份間於福山試驗林進行鳥類繫放活動。共捕捉繡眼畫眉1392隻次，記錄頭骨氣室化指標、虹膜顏色、換羽狀況及9項外部測值以期。頭骨氣室化是判定成幼的良好指標，未完全氣室化的個體中93.0％（n＝243）為幼鳥，完全氣室化個體中有69.1％（n＝265）為成鳥，然而絕大部份成鳥（92.9％）頭骨皆達到完全氣室化的程度；繡眼畫眉幼鳥虹膜色偏向土黃及紅棕色，成鳥則較紅。成鳥族群的換羽季節較早於10月前結束，11、12月中仍在換羽的個體皆為幼鳥；9項外部測值皆不足以獨力區別成幼鳥，而以跗蹠長、最大翼長進行成幼鑑別分析時，與原判不合的誤差率頗高為37.4％（n＝155），難以用來區別成幼鳥。依序以頭骨氣室化指標、換羽、虹膜顏色及外部形質鑑別函數配合繫放日期建立成幼判定檢索表，總誤差率為11.3％（n＝551），其中成鳥較高為24.9％（n＝261），幼鳥為4.7％（n＝296）。 繡眼畫眉存活曲線約為第II型，自離巢獨立生活以後第一年消失率約61.5％，第二年53.3％，第三年略高為85.7％。此外，福山植物園內行政區每年4月進入生殖季之繡眼畫眉數量逐年下降，四年內約降低35.4％。 冬季與颱風為繡眼畫眉之兩大非生物性限制因數。大多數颱風來襲以後，幼鳥數量有明顯下降趨勢，然而除安珀颱風（1997年8月）以外成鳥數量卻仍大致穩定，顯示颱風僅對幼鳥數量具有殺傷力；成鳥數量的減少主要發生在冬季，11至隔年3月間減少約47.0％。

To understand the population dynamic pattern of the Gray-cheeked Fulvettas (Alcippe morrisonia) and the variation resulted from seasonality and typhoons, 1392 fulvettas were captured, marked and released during the period from January 1994 to October 1998 in Fushan Experimental Forest station. In order to construct a standard of age identification, skull pneumatization, iris coloration, moult patterns were recorded and 9 external morphological charateristics were measured. Skull pneumatization was the most effective indicator for age identification from Aril to September each year. 93.0% (n=243) among individuals whose skull were not completely pneumatized (the 1st-4th stages) were juveniles and 92.9% of ones whose skulls achieved completely pneumatization (the 5th stage) were adults. Iris colors of adults were more reddish than those of the juveniles whose iris showed yellowish or reddish brown. None of the external morphological measurements alone were sufficient to discriminate adults and juveniles. When tarsus and wing length together were used in discriminant analysis, error rate was 37.4% out of 155 age-known individuals. Finally, a key for age identification was suggested based on skull pneumatization, moult pattern, iris coloration and morphological discriminant function. The error rate was higher in adults (24.9%, n=261), lower in juvenile (4.7%, n=296), and the total was 11.3% (n=55 1). The pattern of survivorship curve of the Gray-cheeked Fulvetta was similar to the type II. Annual disappearance rate varied frome 53.3% to 85.7% since fledging. Besides, population numbers entering breeding seasons (April) decreased 35.4% gradually during this study period. Winter and typhoons were the major non-biological limiting factors of the Gray-cheeked Fulvetta populations. Under the attack of most typhoons, the number of juveniles decreased obviously while that of the adults kept stable except under the attack of Typhoon Amber (August 1997). The decrease of adult number happened mostly in the winter. It decreased about 47.0% from November to March next year.