彰化沿海地區紅樹林結構與鳥類群聚之關係

Abstract

紅樹林擁有許多生態功能，但是過度均質化的紅樹林可能使生物多樣性降低，這些缺點較少在研究中被提及。對於沿海地區的鳥類，紅樹林快速擴張也造成鷸鴴科鳥類數量減少。在鳥類的棲地選擇，泥灘地為水鳥主要的棲地，但前人研究也有觀察到一些陸域的鳥類，會進入紅樹林停棲。許多沿海棲地中也可以觀察到鷺鷥活動。本研究希望探討鳥類在不同沿海地貌、紅樹林結構間的棲地選擇。研究樣區主要位於臺灣彰化縣沿海地區，包含三種地貌─紅樹林、泥灘地與草澤，並將鳥類分為三類群（鷸鴴、陸鳥、鷺鷥）比較。結果顯示鷸鴴、陸鳥中，相同類群的鳥種其棲地偏好相似，而相同地貌的物種組成相似。鷸鴴偏好紅樹林覆蓋度低的棲地，陸鳥偏好覆蓋度高。鷺鷥多利用高的紅樹林。鷸鴴的棲地選擇可能受到食物資源以及避敵策略影響，陸鳥和鷺鷥的行為與棲地選擇有顯著關聯。陸鳥與鷺鷥都在紅樹林停棲，但鷺鷥覓食時會使用灘地和草澤。另外，周圍地景會影響紅樹林的陸鳥物種組成。進行棲地管理時，雖然營造多樣的棲地有助於提高生物多樣性，但面對近年來鷸鴴科鳥類的減少，應該優先保留泥灘地提供遷徙性鷸鴴棲息。

Mangroves provide many ecological functions. However, excessively homogenized mangroves might reduce biodiversity, and these disadvantages have been rarely mentioned in previous studies. In coastal areas, the rapid expansion of mangroves has reduced the number of shorebirds (usually known as birds under Charadriiformes, including sandpipers and plovers). As for bird habitat selection, mudflats are the main habitats for shorebirds. There are some landbirds (birds do not depend on water, but they can also use it when they are in need of water, food, or roosting site) species would rest in mangroves. Egrets (birds under Ardeidae) can also be observed in many types of coastal habitats. This study was aimed to investigate bird habitat selection in different land cover and mangrove structure variables. The study site was mainly located in coastal area of Changhua County, Taiwan, including three land cover types—mangroves, mudflats, and marshes. The birds were divided into three groups (shorebirds, landbirds, and egrets) for comparison. The results showed that for shorebirds and landbirds, species bellowing to the same group had similar habitat preferences. Sampling plots of same land cover types had similar species composition. Shorebirds preferred low mangrove coverage habitats, landbirds preferred high mangrove coverage, and egrets preferred tall mangroves. Habitat selection of shorebirds might be affected by abundance of invertebrates and anti-predator strategy. Both landbirds and egrets rested in the mangroves, but egrets usually foraged in mudflats and marshes. Moreover, the surrounding habitats could affect the number of landbirds entering the mangroves. Although creating diverse habitats would help to improve species diversity, due to global population decline of shorebirds in recent years, mudflats restoration should be the priority of habitat management in order to protect migratory shorebirds.