墾丁國家公園管理處全球資訊網

墾丁國家公園烏、白頭翁擴散暨烏頭翁保護區劃設之可行性研究(二)

摘 要
關鍵詞：烏頭翁、白頭翁、繁殖、擴散
一、研究緣起：
本研究以烏、白頭翁之雜交、繁殖、及亞成鳥擴散為研究重點，並觀察繁殖成功率，企圖找出影響此兩種鳥雜交的因子，研究範圍為墾丁國家公園及附近地區。
二、研究方法及過程：
本研究經由繫放成、亞成鳥及巢內幼鳥以採集羽毛或血液來供判定性別之用，並經由套上色環與無線電發報器以獲得亞成鳥離巢後的擴散情形。2006年共繫放了123隻成鳥、75隻亞成鳥、以及54隻尚未離巢的幼鳥，並採集羽毛或血液以供判定性別之用。此外，工作人員亦找到93個巢，但因為時間的限制無法追蹤觀察所有的巢，僅完成了53巢的親鳥組合確定。依據已知親鳥的巢來判斷，在新開繁殖的主要是白頭翁，至今在龍鑾潭與國家公園內其他地方都僅找到烏頭翁的巢，但是在楓港、內獅等地則有多種配對組合，尤其內獅應該是位於雜交的核心地帶。各地合計共有25巢繁殖成功，49巢失敗，另有19巢的幼鳥是否離巢狀況不明。
三、重要發現：
追蹤此兩種鳥及雜交配對繁殖成功率的結果顯示，白頭翁的繁殖成功率沒有比烏頭翁的成功率高，此結果與2005年的結果不同，主要是2006年採用了不同的分析方法，計算每巢蛋數時排除了只見到巢但從未發現卵的樣本，計算每巢離巢幼鳥數時，排除了卵沒有孵化的巢。
為瞭解亞成鳥離巢後的擴散情形，2006年不但進行野外觀察，也利用無線電追蹤了11隻亞成鳥的活動狀況。九月及十月在墾丁國家公園西部和新開搜尋有彩色腳環的個體時，發現能看清楚腿部的個體中僅有0.69％的烏頭翁和0.82％的白頭翁有彩色腳環，因此以目視尋找擴散後的亞成鳥效率很低。
資料顯示烏頭翁與白頭翁雄性亞成鳥離巢後多會留在巢區活動，雌性亞成鳥常比雄性亞成鳥早消失蹤影。白頭翁的雌性亞成鳥離巢後會停留相當時間，但目前記錄到烏頭翁雌鳥停留的最長時間僅有22天。兩種亞成鳥每天移動的距離多在成鳥每日正常活動所移動的範圍之內。烏頭翁亞成鳥的夜棲地會隨著主要覓食地點的改變而轉移，但是夜棲點並沒有逐漸遠離繫放點或巢區。白頭翁亞成鳥的夜棲地相當穩定，應和白頭翁研究區的棲地型態有關。
無線電追蹤的資料顯示，烏頭翁亞成鳥兩個月累積活動範圍約250公頃，平均單天活動範圍大約50公頃，白頭翁亞成鳥兩個月累積的活動範圍接近700公頃，平均單天活動範圍低於70公頃。
為評估劃設為烏頭翁保護區之可行性，研究人員在南仁山生態保護區、龍坑生態保護區，及社頂梅花鹿復育區進行烏頭翁分佈與數量調查。結果發現南仁山的烏頭翁族群比較純，但是因為當地的面積很小，棲地也不十分適合烏頭翁的需求，所以當地烏頭翁的族群很小。社頂梅花鹿復育區的烏頭翁族群純度相當高，但是棲地範圍小，烏頭翁族群也很小，若是將保護區的範圍擴大到涵蓋社頂自然公園，則可以增加族群量，但是也同時增加了大量遊客的干擾。龍坑地區的烏頭翁族群較大，雖然雜交個體所佔比例較高，可能是目前最適合劃設烏頭翁保護區的地點。龍鑾潭往關山、鵝鑾鼻方向面積寬廣，烏頭翁數量很高，但是白頭翁與雜交個體也很多，加上是重要遊憩據點，管理上會有多重的困難。
四、主要建議事項：
根據研究發現，本研究提出下列立即可行建議與中長期建議。
立即可行建議─研究烏頭翁亞型是否為雜交個體，定期進行烏頭翁與白頭翁雜交個體分佈與數量監測
主辦機關：墾丁國家公園管理處
協辦機關：中華民國國家公園學會、中央研究院生物多樣性研究中心
立即可行建議—禁止放生行為，建立白頭翁在國家公園中出現的通報機制
主辦機關：墾丁國家公園管理處
協辦機關：地方執法單位、民間保育團體、學校
中長期建議—規劃設立烏頭翁保護區
主辦機關：墾丁國家公園管理處
協辦單位：中華民國國家公園學會
放生活動是加速白頭翁進入烏頭翁分佈區的機制之一，並且墾丁國家公園中的雜交個體數目已相當龐大，若能立即杜絕新的白頭翁入侵，同時採取行動將特定地點之雜交個體移出國家公園範圍，應可以逐漸減少園區內烏頭翁基因被污染的程度。因為威脅到烏頭翁生存的因素是和相近種的雜交，而雜交現象是人類活動移除了兩種鳥之間的隔離機制的結果，所以劃設烏頭翁保護區、以人為的方式維持烏頭翁和白頭翁的隔離，是避免或延緩烏頭翁消失速率的一種策略。

計畫類別：[動物生態]

英文計劃名稱：A study of the dispersal of Taiwan and Light-vented Bulbuls and the feasibility of establishing Taiwan Bulbul Protection zone in Kenting National Park (II)

英文摘要：ABSTRACT
KEYWORD：Taiwan Bulbul, Light-vented Bulbul, breeding, dispersal
This study focuses on the reproduction and dispersal of Taiwan Bulbul and Light-vented Bulbul, hoping to identify factors influencing the hybridization of the two species. Research area covers both within Kenting National Park and the region to the north where Light-vented Bulbuls are found. This year field workers captured and color-marked 123 adults, 75 subadults, and 54 nestlings. These marked individuals were tracked to learn of their movements and autumn dispersal. Blood or feather samples were collected from each marked individual for eventual sexual identification via molecular tools. In addition, field workers found 93 nests and recorded the parental morphology of 53 nests. Judging by the nests with already identified parents, the composition of mated pairs in Hsin-Kai was primarily of Light-vented Bulbuls, while those in Longluan-Lake and other places within the National Park were primarily of Taiwan Bulbuls. Feng-kang and especially Nei-shih had complex combinations of breeding parents. This suggests that Nei-shih is probably at the core of the hybrid zone. This year 25 nests produced fledglings, 49 nests failed, and the fate of 19 nests were not known.
The breeding success of the two species of Bulbuls did not differ statistically. This pattern differed from what was found in 2005 because a new method of data analysis was adopted and all nests with no eggs were excluded from clutch-size calculations and all nests with no young were excluded from fledging-success calculations.
In order to understand the dispersal of the two species, we made extensive field observations and radio-tracked 11 sub-adults. In September and October, field workers searched for color-marked birds in the western part of Kenting National Park and in Hsin-kai area. Based on observations of bulbuls with clear views of their legs, only 0.69% of the Taiwan Bulbuls and 0.82% of the Light-vented Bulbuls were color-marked. This shows that trying to locate dispersed sub-adults through field observations is very inefficient.
Data of this year showed that male sub-adults of both species often remained in the nest area after fledging, and female sub-adults tended to remain a shorter period than male sub-adults. Light-vented Bulbul female sub-adults would remain near the nest sites for some time, while the longest record any Taiwan bulbul sub-adult females stayed near a nest was 22 days. The distances moved by sub-adults of both species were within the distances adults moved in a day. Taiwan Bulbul roosting locations probably shifted with foraging locations, but foraging sites did not move progressively away from the nest site or the location of banding. Light-vented Bulbul did not shift roosting sites with time. This difference probably reflected the habitat differences in our two study sites.
Based on radio tracking results, Taiwan Bulbuls used cumulatively 250 ha area in two months, averaging less than 50 ha per day. Taiwan Bulbuls used cumulatively 700 ha area in two months, averaging less than 70 ha per day.
In order to locate the best location to establish a refuge for Taiwan bulbuls, workers on this study surveyed the population size and distribution of the two species of bulbuls at Nanren Mountain Conservation Area, Longkeng Conservation Area, and Sheding Sika Deer Restoration Area. Results showed that the bulbul population in Nanren Mountain was relatively pure, but because the habitat there was not really suitable for this species, the total population size of Taiwan Bulbuls in Nanren Mountain was fairly small. Sheding Sika Deer Restoration Area had primarily Taiwan Bulbuls, but the population size was also fairly small. If the area concerned is enlarged to include Sheding Park, population size will no doubt increase, but the number of tourists in the area will also increase greatly. Longkeng Conservation Area has a larger Taiwan Bulbul population. Although it contained a higher proportion of hybrids, it may be the best location to establish a Taiwan Bulbul Protected Area. Longluan Lake to Guanshan and Erluanbi Park is a broad region with high bulbul density, but the bulbuls also included Light-vented bulbuls and hybrids. In addition, this area is a major tourist area; thus choosing this area to establish a Taiwan Bulbul Protected Area would involve a large number of management difficulties.

辦理單位：中華民國國家公園學會

計畫屬性：本處委託研究

執行年度：95005

計畫主持人：劉小如

中文關鍵字：烏頭翁、白頭翁、繁殖、擴散

英文關鍵字：Taiwan Bulbul, Light-vented Bulbul, breeding, dispersal