I'm going to go with Robo on this.. the bee trees I know of I leave alone. Set up swarm boxes near them.. Unless this is a chunk of tree someone cut and you retrieved?
I have often found, EVEN when a colony in a tree, old house etc dies during the winter, the cavity is VERY often repopulated that very spring. Its like finding a pot of gold under a rainbow when I locate a new feral colony.
As of this moment, I had only lost one hive when I checked in Feb. But I am very certain, the sub zero temps since then have taken their toll. It is supposed to hit 60 degrees here Monday, for the first time in 5 months, so I can see exactly what I have left.
I expect that I will be splitting my best colony into several nuc's when the queens I have ordered arrive. I had intended to pull light splits from the production colonies as they started to boom.. that may not be an option now. We have to do the best we can with what we have left.