[mdax]

One of my top bar hives was started from a swarm, when I inspected I found there were only one comb of bees and no queen. Several other bars have new comb, about a quarter built out.

If I transfer a bar of brood from a strong hive and give them a mated queen what would be the smallest number of bees to be viable?

 

[Silverbackotter]

One of mine that came out of this winter only had a handful of bees. So I would guess a frame of capped brood and a queen would keep them going.

If you aren't having to buy the queen you don't have much to loose.

Hank

 

[sweetas]

Not quite the same, but I had a swarm about a litre in size do very well

 

[ruthiesbees]

You might also need to give them a bar of pollen/nectar so they can raise the brood. I have a similar situation with TBH#3. My queen, that was ordered in Jan, came in the end of April. Didn't need her anymore because I had issues with TBH#1, so didn't have enough bees for a true split. However, I gave hive #3 the new queen and 4 drawn bars and about 2 cups of bees from a package install from TBH#2. That was Apr 28. On May 3, I moved over a bar of open brood with workers, and another bar of pollen/honey. I've also been feeding them since Apr 28. They are doing well, but of course not going gangbusters like the other 2 hives.

You will probably need to repeatedly give them more resources until their numbers get way up there.