Density and Diversity of Bird Community in Hedgerows Surrounding Farmlands

Hedgerows are the habitat of many wildlife species including avian species. The present study was conducted to examine the effects of size and structure of hedgerows affecting bird community densities in Gorgan Township. Density and diversity of birds and their association with environmental variables were studied using distance sampling method and ordination procedure. Birds and environmental variables were detected within a 25 m radius of each of 94 sampling points. In the study period, a total of 630 observations, representing 15 avian species were recorded. In the summer, House sparrow and Great tit had the highest density while Crested lark and European roller had the lowest density. The first axis of CCA had successfully separated two groups of the birds. The first group, including House sparrow, Crested lark, and Swift had positive correlation with the number of Pomegranate trees, the number of Hackberry trees, and the number of Dewberry shrubs. The second group, including Magpie, European roller, European bee-eater, Blackbird, Great tit, Hoopoe, Long-tailed tit, Nightingale and Carrion crow had positive correlation with the height of hedgerows, the width of hedgerows, the number of Fig trees, the number of Ailanthus trees, the number of Oak trees, the number of Caucasian elm trees and the number of Hedgethorn trees. In the winter, House sparrow and Great tit had the highest density while Robin and Blackbird had the lowest density. The first axis of CCA had successfully separated two groups of birds. The first group, including House sparrow, Crested lark, Hoopoe, and Carrion crow had positive correlation with the number of Pomegranate trees, the number of Hackberry trees, and the number of Dewberry shrubs. The second group, including Blue tit, Robin, Great tit, Long-tailed tit, Nightingale and Coal tit had positive correlation with the height of hedgerows, the width of the hedgerows, the number of Fig trees, the number of Oak trees, and the number of Caucasian elm trees. In the both season (summer and winter), the number of dominant species (N2), Shannon diversity index, the number of species, and Camargo evenness index had the highest values in relation to the width of hedgerows, the height of hedgerows, the density of Caucasian elm trees and Oak trees, while the lowest values of diversity indices was correlated with the density of Hackberry trees, Pomegranate trees and Dewberry shrubs. The results of this study highlighted the importance of size and structure of hedgerows for conserving of density and diversity of avian species leading to conservation of biodiversity.