During times when nectar is scarce, bees have been known to go and take honey from other hives. This is known as robbing. Like a feeding frenzy, bees will start taking from another hive until there is nothing left. It can devastate a hive very quickly and leave your hive starving. Fortunately, there are several things you can do to prevent a hive from being robbed and possibly stop a robbing if you see one starting.
Keep your hive strong. Inspect your hive regularly. Make sure the population is high and the bees are in good health. A healthy hive with healthy bees will prevent attackers.
Make sure your bees are well fed. Hungry bees get desperate and will be on the lookout for easy opportunities.
Avoid feeders inside your hive. I recommending placing feed outside the hive. If you use hive top feeders or front hive feeders then intruders may come to take some feed. This will start attracting bees from other hive to start robbing.
Signs of Robbing:
Lots of activity in front of a hive. Almost like a swarm.
Bees fighting in the front of the hive. You will see tiny bee wrestling matches occurring.
If you see these signs, the best thing to do is put your entrance reducer on the front of the hive. This allows the bees inside the hive to easily defend their position. This is usually enough to stop the robbing from occurring.
Keep your hives strong and protect your honey.