At first the Harriers were a challenge to photograph. They were flying in large circles and were moving too fast to capture easily. We finally saw a gray male circling a thicket and his movements were predictable enough that I caught some fairly sharp pictures by letting him fly into the frame. The Harriers are remarkably similar to owls with their flat round faces. The shape gives them a better ability to hear the small rodents in the grass ahead of them.
As we approached the end of the auto-tour, one of the Harriers finally landed in the grass. It stayed still long enough to get a few more shots. The females are brown instead of gray.
The Harriers range from Central America to Canada and the Arctic, depending on the season, and are also found in Europe. They are year-round residents in the Great Valley. They are fairly easy to identify in flight because of the owl-like head, and a distinctive white band at the base of their tail.
POSTSCRIPT 7/6/17: The Latin name of the Northern Harrier has been changed to Circus hudsonius