http://vimeo.com/37998000#In this video I show footage from two different incidents in which a Great Gray Owl detects an "enemy"...in one case a Bald Eagle, and in the other a Common Raven. Note how the owl stretches itself vertically to become "skinny," and then backs up to be next to the trunk (presumably to blend in) and then presents its narrowest profile towards the raven or eagle.
Filmed in the Sax-Zim Bog of northern Minnesota. Ironically, the eagle incident was filmed on March 3, 2011, exactly one year before the raven footage.
Filmed with a Canon 7D and a Canon 400mm f5.6 lens.