Effect of human-induced forest edges on the understory bird community in Hyrcanian forests in Iran: Implication for conservation and management

Understanding bird species responses to edge effect is critical for effective forest ecosystem management. We studied changes in diversity, density and abundance of bird communities and environmental variables along an edge-interior gradient in the Saadabad-Naharkhoran forested area located within the Hyrcanian forests in Iran. Bird species and environmental variables were recorded within a 25 m radius of 81 sampling points. Distance from the edge had significant impact on the abundance of some species including Great Spotted Woodpecker, Nuthatch, Treecreeper and bark gleaning birds. Among diversity and evenness indices, Simpson diversity index, Shannon diversity index, and N-1 and N-2 indices showed significant differences. Bird species showed different density patterns in our study. Some species such as Great Tit, Nightingale, Carrion Crow and Black Bird responded positively, and Great Spotted Woodpecker, Nuthatch, Wren and Blue Tit responded negatively to forest edge conditions. Bird community analysis divided bird species into two main groups. The first group includes Pheasant, Nightingale, Jay and Blackbird which showed positive responses to edge effect and had a high correlation with variables such as ground cover, number of trees with dbh 12-20 cm and temperature. The second group consisted of Treecreeper, Great Spotted Woodpecker, Green Woodpecker, and Nuthatch which showed a negative response to the edge effect and a positive correlation with snag and log dbh, snag and log height, the number of trees with dbh 100-300 cm, canopy cover, life litter depth and dbh of the trees. Results obtained from this study can be important in conservation and management of bird communities in remnant Hyrcanian forests. Also, protected areas in some parts of Hyrcanian forests can be selected based on environmental variables with a positive correlation with edge-eluding species. (C) 2016 Elsevier B.V. All rights reserved.