Density and Diversity of Cavity Nesting Bird Community in Golestan National Park, Iran

This study was designed to examine the effects of environmental variables affecting density and diversity of cavity nesting bird community in Golestan National Park. 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 122 sampling points. The first axis of CCA successfully separated two groups of the birds. The first group (namely secondary cavity-nesting birds), including Wren, Great Tit, Coal Tit, Robin, and Red-breasted Flycatcher had positive correlation with the number of trees less than 10 m in height, the number of trees with dbh of less than 20 cm and 20-50 cm. The second group (namely primary cavity-nesting birds), including Great-spotted Woodpecker, Lesser-spotted Woodpecker, Black Woodpecker, Nuthatch, and Treecreeper had positive correlation with tree height, snag height, snag dbh, snag decay stage, log height, log dbh, log decay stage, and the number of trees with dbh more than 100 cm. The number of dominant species (N₂), Shannon diversity index and Camargo evenness index had the highest values in relation to the height and dbh of sangs, the height and dbh of logs, the number of tall trees with dbh more than 100 cm and advanced stages of decay, while the lowest values of diversity indices were correlated with the number of trees less than 10 m in height and the number of trees with dbh of less than 20 cm and 20-50 cm. The results of this study highlighted the importance of habitat variables, especially snags, logs and old trees, for conserving and enhancing of birds especially cavity-nesting leading to conservation of the forest ecosystems