極端氣候對水雉（Hydrophasianus chirurgus）繁殖成功的影響

Impact of Extreme Weathers on Breeding Success of Pheasant-Tailed Jacana (Hydrophasianus chirurgus)

水雉是行政院農業委員會公告的保育類動物，在台灣本島一些濕地偶可發現，族群數量十分稀少，且僅局限於少數棲地繁殖。2006至2008年間於高雄縣舊鐵橋人工濕地，每年都持續出現水雉的繁殖。自2008年1月起至12月止在此濕地進行繁殖調查，發現水雉活動大部分集中在浮葉植物生長茂密且人爲干擾較少的區域，繁殖前濕地內最高族群量爲6隻，進入繁殖季後僅剩1對在此繁殖。在2008年繁殖季中，共築巢5次，總計產下18顆蛋，平均產卵數爲3.6個（n=5），但都繁殖失敗未發現有雛鳥孵出，每個繁殖巢中蛋出現存活的時間平均爲6.4天（n=5），繁殖失敗後到再度築巢產下另一巢第一顆蛋的平均間隔時間爲11.5天（n=4）。5個巢均位於同一水池面積約爲25×30m的印度莕菜植群中，新舊巢間距離平均爲4.5m（分別爲8、1、6及3m）。2008年水雉在舊鐵橋人工濕地繁殖失敗的原因皆可歸因於氣候因素，每當颱風、颱風外圍環流或區域性的大風雨，常造成繁殖巢材流失或分離，以致巢內的蛋掉入水中，由找到殘留在水下植物基部的蛋可以得到證實。爲考慮氣候因素對水雉繁殖的影響，未來繁殖棲地的營造應該增加浮葉植物的密度，植物種類也應以葉面積較小的浮葉植物較爲適合。

Pheasant-tailed jacana is catalogued as a rare and precious species of bird protected by law in Taiwan. It is found occasionally in wetlands and breeds only in a few habitats. At the Old Bridge Artificial Wetland in Kaohsiung County, jacanas bred yearly from 2006 to 2008. In January to December 2008, I made field observation and found that they were mostly in areas of the wetland with dense floating-leaf plants and less human interferences. There were 6 jacanas in the pre-breeding season but only a pair remained during the breeding season. The pair built five nests and laid a total of 18 eggs; average clutch size was 3.6 eggs. However, all of the eggs failed to hatch after an average incubation period of only 6.4 days. The time intervals of the nest buildings averaged 11.5 days. The five nests were built in an area of 25×30m covered with floating-leaf plants (Nymphoides indica). Distance between a newly built nest to the previous one for the 5 nests were 8, 1, 6 and 3m, respectively, at an average of 4.5m. Their breeding failures were attributable to extreme weathers due to typhoons, circumfluence of typhoons, or local storms that destroyed the nests, causing eggs to fall into water. They were proved by findings the eggs at the base of floating-leaf plants in water. With consideration of the impact of extreme weathers on jacana s breeding, it is recommended to improve its breeding habitat by enhancing the density of the floating plants with smaller leaf plant varieties.