本研究利用墾丁氣象站的都卜勒氣象雷達之回波圖,分析2014年9月1日至9月30日赤腹鷹(Accipiter soloensis)過境恆春半島的鷹群路線、數量、結構、時間、飛行高度、飛行速度與風向關係,並與地面調查及先前的研究比較,探討當季地面調查赤腹鷹短少的可能原因。研究期間記錄了139個過境赤腹鷹群,鷹群數量介於163~9,734隻,共205,267隻,其中73.82 %選擇陸路,由恆春半島南端鵝鑾鼻與貓鼻頭南遷,26.18 %選擇海路遷移,並發現少量鷹群會由西側過境,此為首度發現。與地面調查的結果比較,雷達估算地面調查的遺漏量為115,737隻,遺漏比例為總過境數量56.38 %,其中以時間性遺漏量最多,佔總遺漏數量49.24 %。規模介於1,000~2,999隻的鷹群數量佔總過境量51.08 %。過境時間介於6時至15時,選擇陸路與海路的鷹群其主要過境時段分別為8時與9時。鷹群在進入雷達掃描範圍時的飛行高度下緣介於42.08~140.6 m之間,離開雷達掃描範圍時的飛行高度上緣介於41.73~332.4 m。飛行速度介於31.19~78.64 km/hr。過境鷹群與風向之關係以選擇順側風的鷹群最多。
This research used the echo image of Doppler weather radar to analyze the migration behavior of migratory Chinese Sparrow Hawk (Accipiter soloensis) in September 2014 on Hengchun Peninsula. We measured and recorded the pattern such as flyways, flock size and dimesion, arrivial time, flight altitude and speed, and wind condition. We further compared these data with ground observation and result of 2005 to examine possible reason of the dramtically decreasing bird count indicated by ground observation in September of 2004. During the study period, radar images showed 139 flocks with size ranging from 163 to 9,734 birds. A total of 20,5267 sparrow hawks were estimtated by radar, and among them 73.82% migrated by land via Eluanbi and Mobitou while 26.18% by sea, with a few passed though western peninsula, which was never found before. My reuslt showed that ground observers underestimated the bird number by 56.38% (115,737 birds). Temporal omission accounts for 49.24% of all omissions. Flock size between 1000 and 3000 birds accounts for 51.08 % of all flocks. The species arrived from 6:00 to 15:00 with number peaking at 8:00 and 9:00 for land route and sea route, respectively. The minimum flock altitude observed when flock were shown on the radar image ranged from 42.08 m to 140.6 m and the maximum flock altitude ranged from 41.73 m to 332.4 m when leaving radar image. The bird flew with speed of 31.19 to 78.64 km/hr. Most flock moved under tailwind direction.