It has been said that juvenile male Harriers have paler underwing coverts than juvenile females. This is not really true, there is considerable overlap, and sexing juvenile Harriers based on plumage is inaccurate at best. The eye color does differ in juveniles (males yellowish, females brown), but that is almost impossible to see in flight. And, shape and flight style of males and females differs slightly but it takes lots of practice to be comfortable noticing this. Females are of course larger, but this is really only noticeable with a direct comparison. The best way to sex juvenile Harriers in the field is NOT TO! Check out these birds below (shown small for a reason), would you feel comfortable telling the sex of any?