Mating Chestnut-Backed Chickadee?

I was in the backyard looking to see what birdies might be lurking out there when I heard a very high pitched, trilly kind of call. I found the source in our Snowball bush, two chestnut-backed chickadees. They were chasing each other around the shrub for a while and then landed on a couple of branches. One was above the other, when the one on the lower branch, again started his (I'm assuming the gender) singing again. Only this time, I noticed he was holding his head high and fluttering his wings very rapidly at his sides the whole time he was belting out his trilly song. The female (again, assumption) was above him but watching him very closely. He continued to sing for a minute or so and then they both flew off into the Walnut tree. It was very cool to see!

Fueling up for the courting?

Here he is singing and fluttering. Kinda grainy but I think you can still see.

Here she is, watching him do his dance!

We wish you all good birding!