I watched a bird hierarchy in action from my work window the other day. There was a loaf of bread on the roof of the autobody shop that I look over and a bunch of pigeons were pecking away at it. Next thing a crow shows up and starts menacing the pigeons, who back off but keep trying to get little pecks in without getting too close to the crow. Next thing a seagull arrives forcing the crow to back off but at this point the pigeons get a little bolder and peck on the other side of the loaf from the seagull. The seagull was trying to drag the enormous loaf away but had to make do with dragging it across the roof. The crow kept menacing the pigeons but wouldn't get anywhere near the loaf until the seagull was gone. The pigeons out-waited them all and ate their fill quite happily.