We got up at 4:00, quite a feat for a couple of night owls, and drove down to the refuge in time for a 7:30 van tour which took us to the scene of the action. There we were allowed to set up cameras and spotting scopes behind a line about 200 ft from the lek. The weather was dark and cloudy so the 400mm f/5.6 camera lens was pretty marginal at that distance. Another birder next to us was using a massive 600mm f/4 lens and she was complaining as well.
Here is a view of the lek, a region of short grass where the males can be seen easily.
These are cropped and enlarged images of the Prairie Chickens in different poses. All of these are males. They have orange air sacs on the side of the neck that they inflate to make their "booming" noise. The "ears" sticking up are actually long feathers that normally lie flat and cover the air sacs.
Occasionally, the males will leap into the air and flutter back down a few feet away.
As a special bonus, as we were watching the lek, a Northern Harrier began hunting in the field to our right. It did not appear interested in the Prairie Chickens. The shot shows the Harrier "hawking" over potential prey.
We also saw some Black-Bellied Whistling Ducks, Red-Wing Blackbirds, and Turkey Vultures.