Correction to my last post: The melody of "Wilhelmus van Nassauwe" is secondary for this song; in an earlier songbook I found out that it was sung to the tune of an older hunting song, which fits well to irregular troops.
The tune is best known as the beginning to Eichendorff's song Students of Prague and starts: Nach Süden nun sich lenken die Vöglein allzumal... (The birdies are flying South now)

Wilfried