大肚溪口與鰲鼓渡冬短耳鴞（Asio flammeus）食性初探

Winter Diet of the Short-eared Owl Asio flammeus (Pontoppidan) at the Augu Farm and the Tatu Rivermouth of Taiwan

大肚溪口位於臺灣中西部，是臺灣目前所設立之海岸保護區中面積最大的。為瞭解底棲動物群聚現象及其與土壤重金屬含量之關係，本研究選定9個固定採樣站（station），每隔三個月於各採樣站設置一個樣區，採集樣區內的底棲動物，調查工作自2000年1月至12月，共四季，取得36個樣區資料，並分別檢測樣區內水體之鹽度、pH值、溶氧飽和度及土壤中鎘、鎳、鉛、鋅、鉻、銅、砷、汞等8項重金屬含量，以探討底棲動物群聚與環境因子之關係。結果顯示，不同樣區間之區別明顯，而季節的差異則不甚明顯，水質及土壤重金屬含量皆會影響底棲動物群聚。由所設置的9個採樣站採取的生物體樣本，進行8項重金屬含量的檢驗，分析顯示鎘、鋅、鉛、鎳、鉻、砷在貝類中之含量高於蟹類，再對應分析土壤的8項重金屬全量檢驗值，各樣區的底棲動物體內重金屬之含量雖然有差異，但不若土壤重金屬含量在各樣區的差異大，反而物種的差異大些。 We collected 129 pellets of the short-eared owl Asio flammeus Pontoppidan (1763), 82 from theAugu Farm and 42 from the Tatu Rivermouth area, during the winter periods of 1995 to 1996 and 1999 to2000. The pellets were 20.31 3.66 cm3 (mean standard deviations) in volumes and 2.3 1.3g in dryweights. They consisted of five taxonomic groups of preys, small mammals, birds, reptiles, insects, andearthworms, for those from the Tatu Rivermouth, and the same groups except earthworms for those fromthe Augu Farm. Small mammals were the most dominant, and then followed by birds, insects, reptiles,and earthworms. The average percent compositions in terms of the total number and total weight(biomass) were, respectively, 61.0% and 65.4% for small mammals, 20.8% and 28.5% for birds, 13.0%and 3.5% for insects, 4.2% and 2.5% for reptiles, and 1.0% and 0.09% for earthworms. For the preyitems identified, the Formosan striped field mouse Apodemus agrarius occupied 30.4% of the total preybiomass, while the brown country rat Rattus losea was 15.3% and thrushs Turdus spp. were 10.6%. TheFNB value and food evenness were, respectively, 7.41 and 0.799, which were higher than 1.87 and 0.435in North America and Europe.