Foraging behavior of the Great Spotted Woodpecker (Dendrocopos major) and the Middle Spotted Woodpecker (Dendrocoptes medius) during breeding season in the Białowieża National Park, Poland

The Great Spotted Woodpecker and the Middle Spotted Woodpecker during the breeding season in the Białowieża National Park forage mainly on the same tree species: European hornbeam, small-leaved lime, pedunculate oak and Norway maple. Therefore, it seems that they should forage in different sites on a given tree species or use different foraging techniques to minimize competition for food. Our research aimed to find out if this is in fact the case. Foraging observations of woodpeckers were carried out between 1999 and 2011 in April, May, and June. We found no differences between both woodpecker species in the choice of foraging sites on lime, hornbeam, and maple trees. In contrast, a significant difference was observed for oak trees, where the Middle Spotted Woodpecker foraged mainly on trunks, whereas the Great Spotted Woodpecker mostly on branches. Significant differences in the frequency of foraging techniques between the two woodpecker species were observed for lime, hornbeam, and oak, whereas no such differences were found in the case of maple. The differences in the foraging techniques of the woodpecker species on individual tree species is a factor that minimizes competition for food between them, while allowing them to forage at sites with similar parameters. The exception is oak, where foraging sites are spatially separated. This finding, and, at the same time, the difference in foraging techniques between the two species of woodpeckers, may suggest that oaks are an important source of food resources for which individuals of both species compete.