Foraging sites of the Eurasian Three-toed Woodpecker (Picoides tridactylus) in relation to sex in primeval forest stands of the Białowieża National Park

Abstract

Despite a clear preference of the Eurasian Three-toed Woodpecker Picoides tridactylus for spruce trees as foraging sites by both males and females, some studies showed intersexual resource partitioning that allows competition for food to be minimized. The objective of the study was to characterize foraging sites of the Three-toed Woodpecker in the primeval stands of the Białowieża National Park (BNP, Poland) in relation to sex. Although the woodpeckers foraged on seven tree species, both males and females foraged predominantly on spruce (83% and 90% of the observations, respectively). Selection indices showed a significant preference for dead spruce trees for both sexes and additionally for live spruce trees in the case of females. Spruce trees where woodpeckers foraged were twice as thick as those available, regardless of whether they were dead or alive. The only feature differentiating the feeding sites of males and females was the diameter of the part of the tree at foraging locations. This suggests that there is some niche partitioning between the sexes of the Three-toed Woodpecker in primeval stands of the BNP. Our research clearly showed that even in the very rich environment of the BNP, abounding in various forms of dead wood, large dead spruce trees are crucial for the Eurasian Three-toed Woodpecker.