Great grey owls are crepuscular and nocturnal hunters. They are difficult ot find but relatively tolerant of owl-watchers. Most of Yellowstone’s great greys migrate to lower elevations in the winter nut some stay year round. I had never seen or heard of a great grey owl at the time I saw this one on Blacktail Plateau. Fortunately I did not have to know what it was to marvel at it in the gently falling snow.