Black and Blue

"As the crow flies" is a phrase I've heard all my life and from my childhood understood it to mean the shortest possible distance between two points, and not necessarily the distance one must really travel to get there.  I never thought much about what it really meant or where it came from until much later in life as I watched the crows around here actually fly.  They do seem to almost always be going somewhere with a great purpose, nose down and flying quickly in a straight line.  Seldom do I see one take a short jaunt (unless he's eating road kill and just moves to get out of the way of my car).  Seems they always go somewhere a half mile or more away.  Sometimes it's like if they wanted to go fifty yards south, they would first fly a mile north, turn around, caw a few times, and fly a mile and fifty yards south, straight as an arrow both ways.