These interesting Northern Harriers were photographed in Fort Worth and Dallas, Northcentral Texas in the '90s:-
A) this adult female type at Village Creek Drying Beds, Fort Worth is reminiscent of nominate cyaneus in that P8 has only four dark bars (plus tip; per Pyle Part II), the underside of the tail seems to show rather sparse and irregular dark marks, and the head and underbody seem to lack warm tones:
B) This ringtail type in Dallas county was seen to fly in low at a resting flock of Ring-billed Gulls and grab one from the panicking flock that saw it too late; it managed to stay on top of the gull and eventually kill it, despite that fact that Ring-billed Gull averages 25% heavier than Northern Harrier (per Sibley Guide):
