Spring is here?

What is going on?  Mid-winter and temperature in the 70's.
And what does this mean for the bees.  I know that they start a spring build-up, usually in late February.  However, what stimulates the build-up seems to be pollen and the girls have been bringing in a lot of pollen for a couple of weeks.  I decided today to add supers (how appropriate for super bowl Sunday). 
I had added a second brood box to #3 12 days ago, so I took a look to see if the bees were availing themselves of the added space.  They were.

Nectar and pollen

Brood with pollen and nectar

These are two adjacent frames from the top box.  Remember, these frames were empty drawn comb when they were put in the hive only 12 days ago!
I put the super on #2 without looking in.  I looked into the top box of #1 and there were two frames with an excellent brood pattern; I looked no further.
The hives all seem very healthy and are in the midst of the spring build-up.  It is a good thing I added the supers as they need the room and the added space helps in swarm control.  I considered putting in drone frames (for varroa control) but I could not decide which box to put them in and I was tired.