Fine-scale habitat use by black woodpecker Dryocopus martius: A year-round study in the Hyrcanian forest, Iran

We investigated the fine-scale habitat use by black woodpeckers all year round. We aimed to describe what environmental factors mostly affect species occurrence at a fine-grained scale in the Caspian Hyrcanian forest, Northern Iran, in a poorly studied portion of the species range. Presence and absence of birds and habitat variables (forest cover types, structural and complexity characteristics of vegetation and topography) were measured within a 25-m radius at 103 sampling points, and seasonal models for habitat selection were built. Plots occupied by woodpeckers consistently showed typical characteristics of old forests, with a high number of snags and many large trees (diameter at breast height > 20 cm and tree height > 20 m). Despite such a consistent association, the comparison of occurrence probability according to the most supported models across different seasons showed significant differences in habitat suitability between summer and autumn and between autumn and spring (P < 0.05), and marginally significant differences between winter and spring and winter and summer (P < 0.1). Such a difference revealed the occurrence of slight seasonal variation in habitat use at a fine scale. Due to the marked preference shown by black woodpecker for forest habitats with beech cover type and mature forest structure, it is essential to control severe exploitation of such habitats. Habitat suitability is strongly affected by the abundance of snag and old trees, the conservation of which is crucial for the species and likely for several other ones dwelling in the same forest habitats. black woodpeckers are associated with mature forest and the species conservation depends to a large extent on how forests are managed.