.>So this is obviously not navigation error (exception: neonics?). Are these foragers looking for weak hives to exploit?

My guess is that these bees are finding themselves a long way from home at dusk - perhaps through being caught out by bad weather - and then just joining the nearest colony that they can find.  But that is just a guess..<<


That happens, as does influxes of bees if a truck full of bees stops nearby.  But our counters show that this 'loss'/'gain" plays out all day long.
We had 27 colonies with bi-directional counter running simultaneously throughout the spring - fall, at three different geographical locations for five years. 

The 'traditional' drift - down lines, with wind occurs.  But the weak colonies staying weak, the strong colonies staying strong is obviously not simply drift.
When we simulated bees lost from a truck on a highway, we saw bees coming into apiaries and heading for the 'collector' colonies, which could be anywhere, including the center of the apiary.

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