We often have a male that takes more nest boxes. This happens because its instinct tells him to find new places to build nests. You noticed that they do not like to lay a second batch of eggs in the same nest box, especially if the nest box is small. Also their current chicks disturb them and often even climb over the eggs. You can easily see that the males prefer to sleep in any other place than their nest boxes during the night. If the male finds an empty nest box and he gets to sleep there for 1-2 nights, he becomes the master of the box.
The first thing that must be done to avoid this is to make sure all the nest boxes without a “master” are closed. This way, other pigeons can’t take them. When you introduce a new male to the empty nest box, you must keep him closed in the box for a few days, and then you must make sure no other pigeon takes his box until he knows to get back to it and feels the owner of the box.
If another pigeon already has a nest box that you want to give to a newly introduced male, keep the first one closed in his nest box until the new one gets used to his new box. Try to put another pigeon with him when he’s inside, and if he beats it, taking it out, most probably, he’s the owner of the box. However, you must keep an eye on them after you release the initial owner, because it will go for the box for sure in the beginning. If they fight really bad, catch him and let the real owner beat him (gently) and then drop him outside the box. Repeat this if he goes for fight again. If the new owner can take him out by himself, you won. If not, repeat until the bad guy remains in his right box.
A pigeon that takes more boxes even if you try hard to educate him is a real trouble. There’s another way to calm him down – remove him from that loft room, keeping him in another loft for 1-2 weeks. Most probably, he’ll be a good guy after that, when you bring him back (don’t forget to lock his nest box while he’s gone!).
Another thing that must be done to avoid these problems is to close all the nest boxes from which you sent pigeons for a race. The ones that remained at home will take over their boxes immediately and the tired pigeon coming from the race will have to fight instead of rest when he gets back – not good!