The Great Spotted Woodpecker is the most common and widespread woodpeckers in Europe.
It has black and white plumage, a prominent oval-shaped white patch on each wing and a red underbelly (trousers). 
Males have a red patch on the rear of the head which females don't have.
Juveniles can be identified by their red crown (clearly visible on the photos) which they loose after their first mould (August - September)

A juvenile. Haff Réimech Nature Reserve, Luxembourg, 13 August 2024