I believe it is very good to have at least two birds in a home. They do not need to be caged together to enjoy one another's company. They love to interact from inside separate cages. Our first two birds were our bourkes and our senegal, and they used to engage in parallel play and eating. The senegal imitated the bourkes, and both loved to chatter back and forth. Now I have a lot of birds, and they all seem to enjoy chattering together and eating at the same time and playing at the same time.
I happen to have both a maximilian pionus and a parrotlet. Although my first two birds were from separate continents, I do find that all of my South American birds seem to communicate a bit better with one another than with my African birds, who seem to communicate the best with one another. This doesn't mean they don't like the birds from the other continents, but they really, really, really enjoy someone from their own continent. (I also now have two Australian birds, but one of them is very new to our home, so I don't know if the two birds from Australia will form a special bond or not.)
I do not allow my parrotlet and my pionus to have physical contact with one another. The pionus could easilly kill the parrotlet, but the parrotlet, I am told, could also do quite a bit of damage to the feet of the pionus.
I do, however, let them out of their cages together as long as I am in the same room. The parrotlet is flighted, but the pionus doesn't fly. She just stays on her play stand. So far, the parrotlet doesn't fly too close to the pionus, but I suppose it could happen. My pionus is very gentle with my other two little birds, so I don't worry that she would be aggressive toward the parrotlet, but if the parrotlet ever tries to get too close to her, I won't let them out at the same time any longer. I know the pionus would never be the instigator of aggression toward the parrotlet, but I also know that if the parrotlet started to attack her, she would kill it in self defense. She is very good at reading the other birds, and she will move herself away if she can.
If you have found a white cap that is already gentle, go for it. White caps do have the reputation of being the least reliable as a species of all pionus, but individual white caps, if they are sweet, are as sweet as any sweet individuals of the other species. I do not know if they are as tolerant of other birds as are the maxis, but, you always have the option of only letting one bird out of its cage at a time if you need to do that. By the way, white caps are quite a bit smaller than maximilians and bronze wings.
Last edited by nanay; 10-17-2011 at 08:03 PM.