Habitat Selection Of Egrets Based On GIS Technology

Egret is a kind of widely distributed wetland water bird. Due to its high demands on the environment, it is an important indicator species of environmental quality. Since the opening of Xixi National Wetland Park, throngs of visitors have been posing a serious interference on wetland birds, and the surrounding urban constructions have also reduced living spaces of birds and other animals.This paper takes the egret as the research subject and analyzes its chronological dynamics and spatial differences to reveal the relationship between the ecological processes and habitats from the perspective of environmental factors. By constructing GIS models of egrets' habitat, this paper reveals the relationship between ecological health and human's impact, providing a significant basis for wetland construction, protection and management.The data concerning the landscape required for the research mainly comes from two remote sensing images:the 2006 and 2009 remote sensing images respectively. Remote sensing data of 2006 is a King Quick bird image, and that data of 2009 is a spot panchromatic one. The data also makes references to the Xixi Wetland construction layout and functional zoning maps. The remote sensing survey proves that wetland habitat area comprises 41% of the total Xixi Wetland Park and non-wetland habitat area accounts for 59%. Many pond habitats and river habitats with a quite good connectivity within them constitute the main characteristics of the habitat type of Xixi Wetland Park.From the observations of the 79 observation points in Xixi National Wetland Park, it can be found that there exists a great difference among the frequencies of the occurrence of egrets in each observation point. No egrets are detected in 40 observation points, accounting for more than fifty percent of all observation points. Thus, it can be concluded that not all spots in Xixi Wetland Park are suitable for the survival of egrets. Chronologically, the period from May to December witnesses the gradual decreasing of observation points that can observe egrets. From the perspective of the distribution area, egrets appear mostly in the inner parts of the park and they can hardly be observed on the periphery of the park. In addition, there is a great difference among the situations of egrets in different open areas of Xixi Wetland Park, which shows the serious impact of the number of visitors on egrets.To reflect the interfering impact of roads and buildings on egrets' habitats, after testing, the paper confirms the ideal buffer distance is 100 meters, and makes use of GIS to analyze the percentage of areas of different habitat types in each observation point, and the analysis is based on different frequencies of the occurrence of egrets in different observation points. The results show that the larger the water area is, the smaller the building area is, and the larger the area of other vegetation (grass, agricultural land) is, the farther away from roads and buildings the habitats are, the better survival chances the egrets will have and vice versa is not favorable to the survival of egrets.From the above findings and with the basis of the analysis of a large number of survey and data, this paper confirms the relationships between diverse habitat factors of egrets, such as road-interference distances, vegetation types and food conditions, and interference conditions. These all affect the construction of the proper model of egrets'habitat. After testing the model, it turns out that the accuracy rate reaches 92.3%, hence the model has a high credibility and practical value and can provide habitat protection and planning for wetland parks.