Keeping honey bees comes with its own responsibilities. To prepare for winter, you may need to mix multiple bee colonies together into one big hive in order to strengthen their resources throughout the winter. Weak bee colonies may not survive the onslaught of winter. It is always recommended that you combine them so that you will still have some bees left after the cold season is over. If you insist on keeping the weak colonies separate all winter, you will end up losing most of the bees.
Combining colonies is also done for hives that have lost their queens.
You must understand that you cannot just combine two colonies without some sort of an introductory adjustment period. The worker bees will fight to death, and the queens can end up being killed during the process. Thus, the introductory period is the time where you combine the colonies subtly and gradually.
Combine bee colonies by first putting a newspaper between them. The bees will tear holes on the newspaper so they can fight, but they cannot tear the paper right away. The colony odors will slowly mix during the time it takes for the bees to destroy the newspaper between them. Once they have successfully ripped the paper, they will not fight anymore, because the two colony odors will have been completely homogenized by then.
A sheet or two of ordinary newspaper will do. Put it on top of the brood box. Place it between the two hives that you are trying to combine. The bees will attack the newspaper. Once the paper has been torn apart and a hole has been created between the two hives, the bees will not fight anymore. Some beekeepers provide slits on the newspaper as a starting point, but doing so is not necessary. You only have to wait one or two days to combine the two colonies.
If there are two queens, you have no choice but to kill the weaker one. The queens will fight, and if you do not destroy one of them, you will end up losing all the queens. There must only be one queen in a bee colony. You can also opt to take care of the other weaker queen away from the colony. Keep it inside a queen cage, feed it with candy, and provide it with at least a dozen nurse bees. You can use it later.