It is actually Feldjäger or Feldjaeger. A Feldjäger is the german military police, kind of, they're mainly after soldiers who are trying to escape the armies or commit insubordination and treasonery. So I kind of doubt that they were present on the battlefield. Just for those who are curious. :3
Until the germans realised that the Pickel on the Haube is like you are shouting to the snipers: PLEASE, FOR GODS SAKE, KILL ME. I AM SITTING RIGHT HERE IN THE TRENCH. There's a reason why the german army stopped wearing it later in WWI.