Intersexual segregation in winter foraging of great spotted woodpecker Dendrocopos major in riparian forests infested with invasive tree species

We investigated the pre-breeding intersexual foraging habitat preferences of the great spotted woodpecker Dendrocopos major in six old, unmanaged riparian forest stands in Central Hungary, which are composed mainly of the invasive North American green ash Fraxinus pennysylvanica and boxelder Acer negundo, and native poplar Populus sp. and willow Salix sp. trees in lower abundances. With the influence of river management, the two invasive species have usurped native tree species in numerous Central European riparian forests. We studied the intersexual utilization of tree species, tree condition, stem diameter, foraging height, horizontal sections, substrate diameter, substrate condition, and foraging technique. The birds showed intersexual segregation in numerous studied variables despite the high niche overlap between sexes. Similar patterns were also found in other woodpecker species as well. We think that the most important part of this segregation could be the difference revealed in the choice of tree species, as males tended to be more specialized for native softwood tree species with rougher bark structure. Despite the high abundance of invasive tree species, neither sex preferred them. The further population decrease of native tree species could increase within-species competition and negatively affect the studied bird species.