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Conservation biology of Chinese Crested Tern Thalasseus Bernsteini and Greater Crested Tern Thalasseus bergiii in Matsu Island Tern Refuge
Seabird conservation,Remote sensing,Social attraction,Unmanned Aerial Vehicle,Platform terminal transmitters,
|Publication Year :||2019|
|Abstract:||黑嘴端鳳頭燕鷗(Thalasseus bernsteini)為IUCN列為瀕危(Critically Endangered)等級之稀有海鳥。目前僅在臺灣的馬祖、澎湖列島、浙江省的韭山與五峙山列島與南韓有確定之繁殖族群。根據本研究與歷史的調查資料，在2004-2017年間，歷年平均在馬祖列島燕鷗保護區觀察到的黑嘴端鳳頭燕鷗成鳥數量為10 ± 4隻，且與大鳳頭燕鷗(T. bergii)共域繁殖。本研究自2011年開始利用社會招引(social attraction)技術吸引燕鷗到合適的島嶼繁殖，也藉由無人機與衛星發報器的追蹤研究瞭解其繁殖棲地與活動範圍的需求。結果發現在地勢較高(高潮位線13公尺以上)、坡度較緩(25度以下)且植被覆蓋率較低(22%以下)的樣區中，有較高機率(50%以上)的大鳳頭燕鷗巢位分佈。而且，黑嘴端鳳頭燕鷗偏好在大鳳頭燕鷗巢位密度較高的區域中繁殖。在活動範圍的部分，本研究發現在水深越淺、離岸邊與繁殖島嶼越近、海水溫度較低且海水葉綠素濃度較高的區域有較高機率的大鳳頭燕鷗分布機率。此外，本研究也透過廣義線性模式(generalized linear model)的分析2004-2017年期間，颱風頻率、海水葉綠素濃度與繁殖群落分散事件對兩種燕鷗族群量以及繁殖產量(成幼鳥比例)的影響。結果發現7-8月間馬祖海域海水葉綠素濃度與大鳳頭燕鷗的年度最大族群量呈現顯著的正相關性，但對黑嘴端鳳頭燕鷗則無影響。此外，我們發現燕鷗繁殖群落常在繁殖初期(5-6月間)遭受干擾後分散至其他島嶼重新繁殖，新的繁殖群落在時程上的推遲導致幼鳥孵化的時間位於颱風頻繁發生的7-8月間，毛羽未豐的幼鳥難以存活過颱風的強風與暴雨。兩種效應(繁殖群落分散與颱風)加成的影響間接導致黑嘴端鳳頭燕鷗連續數年繁殖產量低落。針對這些現象，本研究建議未來盡快釐清燕鷗繁殖群落在初期分散的原因並研擬解決辦法，且強化教育宣傳以提升民眾的海鳥保育意識。|
The Chinese Crested Tern Thalasseus bernsteini (CCT) is likely the most critically endangered seabird species in Asia. Matsu, Penghu, Jiushan, Wuzhishan Archipelagos along the China coastline, and Yeonggwang County in South Korea, are the five areas where this species is currently confirmed to breed. According to census and historical data collected in the Matsu Archipelago from 2004 to 2017, there was an average of 10 ± 4 adult CCT individuals at the Matsu Islands Tern Refuge (MITR) during breeding seasons. Our research showed that CCTs nested with Greater Crested Terns T. bergii (GCT) among most of these colonies at the MITR. Beginning in 2011, a method managing their breeding habitat, we used social attraction to lure both CCTs and GCTs to nest on appropriate island. Unmanned Aerial Vehicles (UAVs) were also used to locate CCT nests and build digital surface models of the protected islands in 2017. The results showed that GCT preferred to nest on high (>13 m above high tide line) and flat (slope < 25°) ground with low vegetation coverage (< 22%), while CCTs tended to nest at areas with higher GCT nest density. We also discovered that GCTs preferred to forage among shallow and cool water areas which were close to their breeding colonies and with high chlorophyll concentration. Generalized linear models were applied to determine environmental influences (e.g. chlorophyll-a concentrations, typhoon frequency, and in-season colony shifts) on breeding individuals and productivity (chick: adult ratios) of CCTs and GCTs from 2004 to 2017. Results showed that from July to August, average chlorophyll-a concentration was positively correlated with the annual maximum number of GCTs, but not that of CCTs. In addition, we discovered that nest abandonment events often happened in the mixed-species colonies fairly early into incubation period, which would cause in-season shifts in colony location and delayed nesting chronology. The extended nest period then causes the hatching time of the young birds to be occurred between July and August, when the typhoons frequently occur. The impacts of in-season colony shift and typhoon caused significant decline in CCT breeding success during 2004 to 2017. To enhance the population size of CCTs, we suggest that more rigorous monitoring should be undertaken to determine the main reason for nest abandonments and in-season colony shifts in the future. Educational programs also need to be developed and promoted in order to raise public awareness for seabird issues.
|Appears in Collections:||森林環境暨資源學系|
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