Last fall I had a hive robbered out by some feral bees. Now, I'd been seeing the ferals still buzzing around the hive through late winter on warm days, I figured they were picking it clean. Turns out, they moved in. Must have happened really late fall and I totally missed it. The other day it was in the low 60's and I saw ferals bringing out dead bees and was all "robbers would not be doing that" and so we popped off the top box, and sure enough there was a nice sized cluster.
So, I apparently have feral bees to keep now!
These ladies are tough, though, let me tell you. Popping the lid a second time I stuffed some fondant into the hive for them and we got chased off by two angry ladies. Also, they'll fly on cleansing flights and bring out the dead when it's about 50 degrees, I've seen them out on the entrance board as low as 43 degrees out. They also seem to always have guard bees on duty at the hive entrance when they are flying, and check out all incoming bees, they're super defensive.
I'm looking forward to keeping them next to a new package of Italians coming in spring, to see how they are as far as disease and pest control and honey production. Not looking forward to how hot it seems this hive of bees might be, but definitely it will be an adventure come spring and summer!