I'm a total newb, so take this for what it's worth, I don't see many bees there. Are you sure that they're OK? Here's what mine did on a warm spring day.
http://www.youtube.com/watch?v=lM0qpkTN7Q0
When I opened the top up, they boiled over. Almost every frame covered. . .
http://www.youtube.com/watch?v=lM0qpkTN7Q0
When I opened the top up, they boiled over. Almost every frame covered. . .