>>Such drift would presumably follow the diffusion model

>Why would one presume this? 

In my experience drifting takes many forms and no assumptions can be safely made.

I bought some blonde packages last year and installed them at one  spot  in a big yard of dark bees.

A while later, I was surprised to see blonde bees showing up in pretty well all hives in the yard.

We  also  are all aware, I am sure, of the effect of having a strong flow in only one direction from a yard where we find the hives on the side near the flow are taller and heavier than the hives on the far side.

Then there are drones...

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