Mason Bees

I have a couple of Mason Bee houses by the patio and they are all a buzz with industrious bees making their nests in the tubes. I was busy potting up some plants when I heard a furious buzzing, a really high-pitched buzz-whine of a bee. I thought it sounded rather odd so I followed the sound back to one of the house and gingerly lifted the house off its peg, thinking that maybe a bee had gotten itself trapped somehow around the back or caught in a spiderweb (sorry spiders, you aren't allowed to eat my bees) and was trying with all its might to get out. As I was standing there, house in hand, staring dumbly at it, out flew the bee. "Ahhhgh!", I said. "Ahhhgh!", said the bee. "What are you doing messing with my house?"
It wasn't in distress, it was big, fat and shiny and very black-blue. A glorious specimen. I now wonder if the furious buzzing was coming from her fanning dry the mud-plugs by which she blocks off each egg from the other in the nesting tube.