Feeding a late fall swarm

A swarm moved into our building in September. Since most late swarms don't survive the winter, it wasn't worth moving them into a hive. They did barely survive, at least until now. Here they are on March 7—just a small cluster and almost no food. With nuc colonies and packages costing over $100, it seems cost effective to give them a little extra care. I've added a Boardman feeder. It took them two days to notice it. Later I'll transfer them to a hive. When I fix the siding, I'll leave an entrance to the old cavity which will act as a bait hive for wandering swarms.