>So I learned something new. Drones will move willy-nilly among hives, even if they are from outside the yard?
> The guard bees don't challenge them?
Not unless it's late fall.
> Any reason why they would choose to squat in one hive exclusively?
They just drift.
>These black drones were in the super-strong hive with a laying queen from last summer, and I saw none of them in any of the other hives.
Don't know, but they drift a lot.
>But why then do the feral bees tend to be black?
I don't know. It didn't used to be that way. Most used to be leather colored Italians around here. Now they seem to be black.
> Are they a hold-over from the few old German bees that perhaps didn't get decimated by the varroa?
Here's a picture of my bees.