Effectiveness of a Bird-habitat Improvement Project in Sihcao Wetlands

27 Mar Effectiveness of a Bird-habitat Improvement Project in Sihcao Wetlands

View Original

Abstract

四草野生動物保護區當中的高蹺鴴繁殖區(A1)及北汕尾水鳥保護區(A2)，於2002-2004年之間陸續進行大規模棲地改善工程，目的在增加高蹺鴴繁殖族群及提昇鳥類多樣性。我們在2003年12月至2010年7月於保護區進行鳥類調查，並對照鹿耳門溪北岸廢棄魚塭的同期鳥類調查資料，以及A2區1998-2000年的施工前文獻資料，評估該項工程是否達到預期效果。結果發現A1區在施工之後，繁殖期高蹺鴴族群量並未逐年增長；度冬期水鳥群聚結構則在2003-2005年之間發生劇烈變動，兩年內物種轉換率達52%，主要改變為水岸高草游涉禽增加、水域泥岸涉禽減少；2005年之後群聚結構才趨於穩定。A2區在棲地改善工程之後，候鳥度冬期的水鳥總個體數並未增加，種類多樣性則非但未增加，甚且逐年遞減；2003-2009年之間水鳥種類多樣性減少21%。A2區施工前的度冬期水鳥群聚結構，在1998-2003年之間沒有明顯變動。但施工及完工之後，於2003-2009年之間，則持續呈現具方向性之改變，主要是水岸高草游涉禽增加、泥灘涉禽減少。由於對照樣區群聚結構在此期間呈穩定狀態，顯示A1及A2區鳥類群聚結構劇烈變動為獨立事件，其原因極可能來自棲地改善工程。是項工程沒有成功增加A1區高蹺鴴繁殖族群，而在A2區，非但未使水鳥種類多樣性增加，反而導致其嚴重銳減。是項工程的必要性未經科學評估，亦未明確釐清課題，且基礎生態資訊掌握不足，導致規劃失當。然而棲地改善的成效評估及生態監測報告並未指出工程未達預期效益之問題，主要原因是監測缺乏目標、抽樣及分析不當、以及結果未正確解讀。我們認為任何棲地改善或復育工程均必須基於生態學資料，並廣納各界建言，避免僅根據特定少數人意見而為之。

English Abstract

A habitat improvement project for wetland birds in Area A1 and A2 of Sihcao Wildlife Refuge was conducted from 2002 to 2004 aiming at increasing breeding population of black-winged stilts (Himantopus himantopus) and bird diversity in the refuge. To evaluate the effectiveness of the project, we conducted bird surveys in the wildlife refuge and a discarded fish farm 2 km away as a control site from December 2003 to July 2010. We investigated bird assemblage change using linear regressions and ordination techniques. Bird assemblage between 1998 and 2000 was compared to that after the habitat improvement in A2. In A1, black-winged stilt population did not increase after the project was devised. The bird assemblage turnover rate was 52% between 2003 and 2005. In A2, bird assemblage was stable before the project, but after the project, bird richness decreased by 21%, with waterfowls increasing and waders decreasing significantly. Bird assemblage at the control site was stable between 2003 and 2009, suggesting that the habitat reconstruction project may be the cause of bird assemblage changes in A1 and A2. The project failed to meet the intended goals due to insufficient evaluation of its necessity, failure to pin down the issues to address, as well as inadequate biological information to begin with. However, the failure was not revealed by subsequent monitoring projects, whose objectives were ambiguous, methods inappropriate and results inaccurately interpreted. We argue that wetlands and their dependent birds are vulnerable and sensitive to habitat changes. As such a much rigorous framework to evaluate, conduct and monitor habitat improvement is urgently required before any such project is launched.