I have had about 20 hives all my live. I have seen sveral times what inbreeding makes in small yard.
It revieles out when you buy every year 2-3 new queen and comapre them to your yard hives.
how it happens:
- you have a good hive and you take from it 10-15 new queens. Next year half of your drones are brothers.
Next year you still have a good hive, and the queen is sister of half yard drones. If you are lucky, next year your all hives are inbreed.
One year I bought 3 queens 300 km away. It revieled that those 3 colonies were after winter same size as in autumn. Other 15 colonies had suffered from nosema and many very badly.
So new queens revieled that my apiary was not tolerant to nosema. and I had made lots of work to get a good bee stock with crossings.
- During last 3 years I have found that my best huge hives have got blood from Carniolans. That waked me up that it is not good thing to take new queens from one best hive.
Now I take queens from several good hives and kick out only queens which are angry, not good laying and so on.
Even if I buy every year new queens, and I rear new queens, hybrid vigour tells that pure best is not allways best.
One year I bought an old queen from professional beekeeper and I told that I need a queen where I can get new queens.
I reared 10 queens. Next spring that mother queen hive was so sick by nosema, that it stopped laying even if it had 4 frames of bees after winter.
So by accident I had reared to half of my apiary nosema sensitive queens.
.I have many more stories, but that is life.