I am assuming you can do spring splits as soon as you have capped drone cells? Yes/no?
As far as capped goes, I've always read that poeple wait until the drone pupae matures to the purple eye stage. Which would make sense because the queen emerges and is ready to mate a lot earlier than drones.
Some people wait until the drones are flying because you want a big population in the DCA area and you don't want the drones from the hive you are inspecting that may be ahead of the other hives in your area.
According to the literature, queens are ready to mate within a few days of hatching. Drones aren't mature enough until 12 days after hatching. Coupled with the 14 day pupae stage for drones ( vs 8 days for a queen), there is almost two weeks difference between a capped to mature queen, and a capped to mature drone.
So yes, if you have capped drone cells, they should be mature enough to mate with a split queen that emerges around 2 weeks after the split. If the hive is actively rearing drones, it would appear that they have some clue that the mating season is approaching. Having an adequate abundance of mature drones, to ensure proper mating, may mean waiting a week or two after seeing the first capped drone brood. Early queen rearing attempts seem to have better success by timing it to coincided with swarm season, while many report that best results only occur after swarm season.
As always - very regional, and Ace makes a good point.
Good luck!
Yes, the rule of thumb is purple eyed drones...I usually wait until I see new drones.
As mentioned, bee colleges always teach to wait until you have purple eyed drones.
Jim