How close is you nearest fellow bee yard? Do you have the only bees within 3 miles of you causing you bees to inbreed? Here I have at least 6 or more bee yards that my queens will mate with.
the distance to fellow is 0,6 km
But when I have mating nucs in remote yards, there are somewhere hives, which I do not know where. I get there Carniolan blood to my Italian queens.
I believe that bee colonies live in empty farm houses.