This late in the year, if you have any robbing going on. As I do, than they could be picking up the dead bees. After the bees fight, I have seen dozens of yellowjackets eating the bees.
They like to hang out at ground level of strong hives, and snatch every little thing that the bees throw out. Even larva, ect. I have seen bees remove larva from the hive, and I was going to get it when they dropped it to see what it was, it looked like the bee handed it to the yellowjacket they took it so fast, within seconds there were over 8 yellowjackets fighting over it. Now that I think about it, they are probably removing some drone brood about now, just watch them, I'll bet thats what they are after also.