What's this butterfly doing?

Here's a sequence I took in my photography class at the Tucson Botanical Gardens Butterfly Magic exhibit. The brown butterfly landed, spread its wings, and didn't budge the whole time the blue one was flying around and landing on it. Finally the blue one flew away. I don't know anything about butterfly behavior. Was this aggression or was the blue one vying for a better spot? Is this the same kind of thing that happens at bird feeders? (See Dharma Bums post of January 25: Choice Blend at the Bird Feeder - which, by the way, contains fine haikus and interesting political thoughts.)