Weird chicken behavior: Why do they act like this?

[OllieOliverCharlie]

I have 6 RIR pullets who are about 11 weeks old. Every night, about 10 minutes before they walk themselves into their coop, they go crazy. They start flying at whoever happens to be walking by. If they manage to jump over their fence (which they have) they will fly onto the person's shoulder/head/arms. I don't understand why they do this, because if we try to pick them up without them flying on us on their own, they run away. It doesn't make any sense! They don't act like this at any other time during the day, only right before they go to sleep. Why do they do this? Is something wrong?

 

[azygous]

In all my years of raising chickens, I've never seen this. I'll be interested in hearing if anyone else has, and what it means.