Brandishing a fierce bill rather than a deadly sword, ruby-throated hummingbirds seem to share the Highlander's philosopy: There can be only one.
Ruby-throats are deadly serious about this. Because they need vast quantities of food to stoke the inferno that is their metabolism in order to survive, they aren’t much into sharing. They claim a feeder for themselves and themselves alone (though a male may let a female feed after she has mated with him), strictly enforcing a zero-tolerance no-fly zone around it.
This leads to fierce, sometimes even lethal, battles. Locked in combat, hummingbirds will come crashing down to the earth. Full contact, you can hear their bills colliding in midair as they attack each other. And if the initial attacks don’t drive off the challengers, then the dominant hummer will simply attempt to run the interloper down. Well-fed as the Lord of the Feeder, he will keep chasing the challenger until it has spent all its energy and perishes accordingly.
What this means is that you will rarely see more than one ruby-throated hummingbird at any given feeder at a time. Imagine my surprise, then, to see six hummingbirds at a single feeder (I also have other feeders throughout the yard). In the picture below, you can even see five them settled down and feeding. I took a bunch of pics, as well as some video, and then just sat and watched in amazement.