金門農耕地之棲地變化及地景組成與鳥類群聚之影響

Abstract

金門農耕地的作物隨季節而改變，以11月至12月種植小麥（Triticum aestivum）、3月至4月種植一作高粱（Sorghum bicolor）以及6月至7月種植二作高粱為主，而島上林地、農耕地、草生地、水塘等各類棲地鑲嵌程度高。本研究主要探討作物類型（小麥、一作高粱與二作高粱）、作物的生長時期（抽穗開花期與乳熟期）以及不同的地景組成對鳥類密度（density）、種豐富度（species richness）、種歧異度（Shannon-Wiener′s index）以及6種常見危害鳥種族群密度之影響；且分別以樣區不同半徑（300m與500m）內的地景組成，檢視對鳥類群聚介量與危害鳥種族群密度的影響是否有差異。我共選取11個小麥樣區、23個一作高粱樣區與30個二作高粱樣區，並利用穿越線法（line transect）及定點計數法（point count）進行鳥類相調查。結果發現，食物資源與季節為影響鳥類群聚與環境之間關係的主要因素。無論在半徑300m或500m的尺度，作物生長時期對鳥類密度、種豐富度、種歧異度以及八哥（Acridotheres cristatellus）、斑文鳥（Lonchura punctulata）、麻雀（Passer montanus）、珠頸斑鳩（Strptopelia chinensis）、紅鳩（Strptopeliatr anquebarica）的密度有顯著影響（p<0.05）；在半徑300m尺度，作物類型對鳥種豐富度、種歧異度與八哥、環頸雉（Phasianus colchicus）、麻雀、珠頸斑鳩、紅鳩的族群密度有顯著影響（p<0.05），而在半徑500m的尺度，作物類型才對鳥類密度有顯著影響；地景組成中以建成地對鳥類密度、種歧異度影響最大，當建成地比例越高則鳥類密度愈高、種歧異度愈低，而鳥種豐富度則不受地景因子影響。因此，探討農地之微棲地變化及農地周圍地景組成與農地鳥類群聚結構之研究，有助於釐清鳥類群聚與環境之間的關係。

Kinmen consists of different land use types, such as forests, agricultural lands, grasslands, ponds, and the others. About 27 percentage of the total area in Kinmen is covered by agricultural land, of which sorghum (Sorghum bicolor L.) and wheat (Triticum aestivum L.) are the most important and widespread seasonal crop in agricultural land. To understand the relationships between bird distributions and agricultural habitats, I studied the effects of cropping practice (crop type of season), crop growing stage (premature and mature period of crop) and landscape composition at two different scales (within 300m and 500m radius of the site) on farmland birds. The study sites where bird censuses were performed by line transects and point counts comprimsed 11 sites in wheat fields, 23 sites in the first cultivated sorghum and 30 sites in the second cultivated Sorghum. Bird density, species richness, Shannon-Wiener’s diversity index, and damaged birds’ density (including Crested Myna (Acridotheres cristatellus), Scaly-breasted Munia (Lonchura punctulata), Ring-necked Pheasant (Phasianus colchicus), Eurasian Tree Sparrow (Passer montanus), Spotted-necked Dove(Strptopelia chinensis), Red-collared Dove (Strptopeliatr anquebarica)) were assessed. The analysis was conducted using multivariate analysis at two different scales: within 300m and 500m level. The results show that cropping practice and crop growing stage were the principal determinants of the bird assemblage and damaged bird density(p<0.05). The bird density, diversity and damaged bird density differed significantly in their landscape compositions at distinct scales(p<0.05). Moreover building was a major factor of the studied landscape variables affect the bird assemblage and damaged bird density. The present results suggest that food resources and season variation were the most important determiants of farmland bird assemblage, and multi-scale analyses can greatly enhance our outstanding of bird distribution and of their interaction with the environment.