Investigating the effect of environmental variables on distribution of three woodpecker species (Black woodpecker, Great spotted woodpecker and Green woodpecker) in Shast Kolateh Forest, Gorgan

Forests are considered as important sources of biodiversity around the world. Nowadays, forest ecosystems have the most important protective role. The forest ecosystems are the main habitat for many wildlife species that among them we can refer to the diverse species of the birds, including woodpeckers. Woodpeckers are considered as the indicator of the forest bird biodiversity. The elevation and forest structure are the most important environmental variables that affecting the woodpecker distribution.
In this study, three elevation classes were selected in the Shast Kolateh forest, namely 0-400 m containing parottia- carpinus- quercus forest type, 400-700 m including carpinus- parottia and parottia carpinus forest type, and 700-1000 m wherein beech trees were considered as the dominant species. The bird sampling was conducted using point count sampling procedure. The woodpecker species and the number of all observations in relation to each species in each of 103 sampling plots were recorded in summer and autumn.
The results of CCA ordination graph for three different woodpecker species with environmental variables and elevation showed that the most abundance of Black and Green woodpecker was occurred in 700-1000 m and 400-700 m a.s.l, respectively. Furthermore, there was no significant relationship between the abundance of Great spotted woodpecker and elevation.  
Discussion and The results revealed that the Great spotted woodpecker and Green woodpecker are more flexible in habitat selection and Black woodpecker unlike to the other woodpecker species is a dependent species to the forest habitats with beech cover type and mature forest structure, so it is essential to control severe exploitation of such habitats.