On the cover we see the 2007 Serbian WWF issue on the black woodpecker. (Dryocopus martius). This is a large woodpecker, 40-46 cm long with a 67-73 cm wingspan.
It lives in mature forest across the northern palearctic. It is the sole representative of its genus in that region. Its range is expanding in Eurasia. It does not migrate.
The plumage of this crow-sized woodpecker is entirely black apart from a red crown. In males, the entire crown is red, but in females only the hindcrown. The sexes differ even as nestlings.
The black woodpecker's flight is straight, not dipping like other woodpeckers. As we see on the stamps, the nest is a tree-hole into which four or more eggs are laid.