Last week I finished medicating (apistan, terramycin, etc) and wrapping up (1 layer tar paper) my three hives.

After being away from the house since then, I left for work this morning at 7am to find that the strongest hive, and only the strongest one, had a huge number of bees clustered on the front of the hive, above the entrance reducer.

Any ideas why on earth they would do this?

Other items to note about this hive.

1) This hive still has some brood developing in it.
2) This hive was SO full of bees and honey that I left it stacked three deeps high.
3) As with the above items, when I finished medicating all the hives, I found this hive had a very large number of drones in the colony.

Any thoughts on this? anything else I should look for or do? :?: