Dryocopus martius
Biggest woodpecker in WP (crow size). All black with red crown (male) or nape (female). Unmistakable. Flight Nutcracker-like, "inefficient" and fluttering, almost without undulations.
Most sounds diagnostic and very far reaching. Drumming very powerful and long (1.8 - 3 sec.) with slightly falling intensity and accelerated ending. Each beat clearly distinguishable as in Tree-toed Woodpecker, but duration much longer. Drumming:[1375]Flight call a characteristic resonant trill "krrreekrrreekrrreekrrree". A characteristic short, sharp and plaintive "keeaaa" with descending pitch often uttered when excited. Song a quick series of "klee" calls resembling Green Woodpecker, but with a purer tone and upward infliction at end of each syllable. A few slower drawn-out introductory calls before the phrase gets going is diagnostic.
Wikipedia: map (se also Xeno-canto below)
Birdlife ecology