The Research Of Coexistence Pattern Of Corvidae Birds In Tiantong, Zhejiang Province

The coexistence mechanism of birds is a hotspot problem of research on avian community ecology. During July 2013 to June 2014, the author conducted field work in Tiantong park of national forest and the surrounding area which is located in Ningbo, Zhejiang province, and investigated the community of Corvidae birds in the area of research by the line transect method. Four common Corvidae birds consisting of Magpie (Pica pica), Redbilled Blue Magpie (Urocissa erythrorhyncha), Eurasian Jay (Garrulus glandarius) and Grey Treepie (Dendrocitta formosae) were taken as the research object. We seted samples in the Corvidae birds’ habitat and collected ecological parameters. According to the data of field plots, this paper dealt with the microhabitat selection, resource partition and interspecific relationships of the four species of birds by calculation and comparison of resource utilization rate, niche breadth and niche overlap. After analyzing the relationships between environmental factors of 10m scale and landscape factors of 100m scale by applying Canonical Correspondence Analysis (CCA), the longterm coexistence mechanism of the four species of birds distributing in Tiantong region was analyzed and the topological structure pattern was drawn out. The research result can provide important reference value for the maintenance mechanism of avian diversity and scientific advice for avian conservation measures of Tiantong region. The results of this paper are shown as follows:1. The resources utilization of Corvidae birdsThe analysis results of 10 kinds of resources utilization rate show that,the bamboo forest is highly used by Red-billed blue magpie (0.21), the coniferous forest is highly used by Eurasian Jay, and the residential area is highly used by Magpie. By contrasting the data of each kind of bird’s utilization rate, it turns out that there are highly significant differences (P≤0.01) between Red-billed blue magpie and the other three birds on bamboo forest, there are significant differences (0.01≤P＜ 0.05) between Magpie (Red-billed blue magpie) and the other two birds. With the MDS analysis results, we find out that difference Corvidae bird has difference preference on resources, it’s the reflection of Corvidae birds’ resource partitioning.2. The multidimensional niche of Corvidae birdsThe analyses of niche breadth and overlap on four dimensions conclude that, the niche breadth index on habitat matrix of Magpie (0.672) and Red-billed blue magpie (0.621) is highest, the annual average difference of Corvidae birds’niche breadth index is not obvious, the annual niche breadth index on feeding matrix of Grey Treepie is a little higher than Eurasian Jay, the annual niche breadth index on foraging space of Red-billed blue magpie (0.725) is highest than the other three birds. The seasonal dynamic of habitat is an important factor that influence the niche breadth index on each dimension. There are complex set relationships relationship among the four dimension. The Corvidae birds broaden the niche breadth to reduce interspecific competition at different periods of time.3.The analysis of environmental factors in 10m scaleThe CCA analysis results of 15 environmental factors show that, the structure of the horizontal direction habitat has remarkable effects on the disposition of Magpie and Red-billed blue magpie, the structure of the vertical direction habitat has remarkable effects on the disposition of Eurasian Jay and Grey Treepie, human disturbance has a significant influence on Corvidae birds apart from the Magpie. Food abundance has a significant influence on all species of Corvidae birds. It turned out that the adaptability to human disturbance of Magpie is better than the other three Corvidae birds, Red-billed blue magpie comes second, while arbor coverage has remarkable effect on Eurasian Jay. The Monte-Carlo test of all canonical axis shows high F value (6.340), and the P value is less than 0.01, which proves CCA analysis to be effective.4.The analysis of landscape factors in 100m scaleThe CCA analysis results of six landscape factors show that, Water landscape has remarkable effects on all species of Corvidae birds, there is a strong dependency between Magpie (Red-billed blue magpie) and three types of landscape including humanities landscape, residential landscape, and grassland landscape. The attraction of woodland landscape for Eurasian Jay and Grey Treepie is higher than other landscape, The distribution of four species of Corvidae birds in agricultural landscape is relatively homogeneous. The Monte-Carlo test of all canonical axis shows high F value (6.038), and the P value is less than 0.01, which proves CCA analysis to be effective.5.Corvidae birds’ecological mechanism of coexistenceThe formation of Corvidae birds’community structure is the result of combined action of various factors including microhabitat selection, niche differentiation, resource partitioning, interspecific competition, environmental factors, and landscape factors. All of these factors reflects the complex coexistence mechanisms of Corvidae birds from different angles and different scales. The topological structure pattern is drawn by these mechanisms. The pattern indicates that the coexistence of Corvidae birds results from comprehensive function of multiple factors.