The Northern Harrier, or "Marsh Hawk" has been well known to me from childhood. If you are a person like me that has spent a serious amount of your life in and around waterfowl marshes it is one of the most commonly seen raptors. With it's low flying, floating style as it slowly jukes over the cattail tops and it's distinctive white rump spot, it is even with it's, unique within raptors, male-female color differences the LEAST confusable raptor. It is as generically as much of a windswept marsh under leaden skies as cattails. But seeing one up close is very difficult. They are always on the wing, rarely perching. And as they vector back and forth looking for mice and insects, they really DO know you're there and without visible effort always float off the other direction.
Norther Harrier (Marsh Hawk)