It's all in how you train your eyes. My wife of thirteen years has learned to spot deer like that too now. She does not hunt, but after years of me pointing them out, her eyes are trained to pick out an an ear, the curve of the rump, the white V on the tail or whatever.
Sometimes she even spots them before I do now.
I've never been good as spotting pheasants in the ditch, but I don't get much opportunity to practice. My uncles in NW Kansas were amazing at seeing the ditch parrots.