I used the word "hovering" because he would flap his wings rapidly to get straight up out of the tall grass and then just stay there for a time before diving back into the grass or flying to another spot, a lot like the aircraft of the same name. "The Harrier, informally referred to as the Harrier Jump Jet, is a family of jet-powered attack aircraft capable of vertical/short takeoff and landing operations. Named after a bird of prey."
And we have concluded, with Kevin's help, that it is indeed a male Northern Harrier.