Re: When to transfer overwintered nuc into brood box??
Some things just come with experience. Everyone manages their hives differently. Its been mild here and my hives have been raising brood like crazy. Pick a nice warm day and open them up to evaluate. Have a deep box ready in case you decide to swap them over at that time. If they are wall to wall inside that nuc box they will appreciate some more room. If you have any drawn comb add it to the deep. Check the honey and pollen stores while your inspecting them.
"Tradition becomes our security, and when the mind is secure it is in decay".....Krishnamurti