屏東地區黑鳶(Milvus migrans)的巢位選擇

猛禽等生態系中的高級消費者常常被當作生物多樣性的指標，並作為保育工作優先執行的對象。透過了解猛禽巢位的選擇機制能作為族群經營管理上的依據，更是維持其族群穩定的關鍵。黑鳶(Milvus migrans)是台灣大型猛禽中與人類活動關係最為密切的，過去曾經普遍分布全島，但推測可能是因為次級毒害、棲地喪失而導致族群量迅速下降。本研究透過(1)巢位尺度(500 m)、(2)活動範圍尺度(5km)兩個不同層級與隨選點位比較差異，分析黑鳶巢位的選擇偏好，並(3)建立巢位預測模型。我們於2021年的繁殖季記錄了位於屏東縣的30個黑鳶巢位。在巢位尺度中，巢位與最近建物、溪流的距離較近；在活動範圍尺度中，巢區距離森林邊界距離、最近夜棲點顯著較短，且顯著選擇森林覆蓋較大，建物、水域覆蓋也較低。巢位選擇的預測模型在兩個尺度中不同；巢位尺度中，人為活動與地理因子兩個模型有較佳的解釋力，說明在小尺度中可能受到鄰近的人為活動與海拔、坡度等不同影響；活動範圍尺度則是森林邊界距離、最近夜棲點預測能力最佳，顯示黑鳶巢位選擇會受到牠們群聚習性的影響。我們發現屏東黑鳶巢位選擇的確在不同尺度受到不同因子所影響，未來可透過這個方式建立更完整的巢位預測模型，讓台灣黑鳶的族群管理資料更趨完整。

關鍵字

黑鳶；繁殖棲地；棲地選擇；猛禽；地景

並列摘要

Being frequently regarded as indicators of biodiversity, raptors are priorities when it comes to conservation. Understanding the mechanism behind the nest site selection of them is essential to wildlife management and a key to maintain a sustainable population. Black kites (Milvus migrans) are the most tightly connected to human activities among the large raptors of Taiwan. Once common and widespread, its population dropped dramatically possibly due to secondary poisoning for the past few decades. In order to find the core habitat for the species, we recorded a total of 30 black kite nests in Pingtung of southern Taiwan during the breeding season of 2021. We analyzed nest site selection by comparing kite nests with random selected sites in home range (5 km) and nest site scales (500 m). For the nest site scale, kite nests are located near human settlements and closer to streams than random. For the home range scale, kites selected habitat that are closer to communal roosts and forest border, with more forest coverage and less human settlements. The nest site selection function also varied in the two scales. Both human activity and geographical model explained in nest site scale, indicating possible influences for black kites. Distance to forest edge, nearest roost explained the best in home range scale, meaning the socialistic nature of the species also has a key role in nest site selection at a broader scale. Overall, our efforts show that different factors affect the nest site selection of black kites across spatial scales, and we can use this method to predict habitat distribution for other parts of Taiwan in future research.