I'll respond as both Adoption Coordinator and parrot home...
We get this question all the time from adopters. Our answer is always the same (outside of the littles that are caged all the times - finches, non hand friendly budgies, etc), we always tell adopters that getting a bird for your bird rarely works out the way the person hopes. Only get another bird if you have the time, space, resources and desire to have separate cage areas, separate play / social areas, separate play / social time with you, space for 2 playstands and so on.
Birds are unpredictable... if a bird is very bonded to their chosen person, they can be jealous and resentful of having another bird in the home. They could openly hate each other and be aggressive to a point its dangerous to have them in the same area at the same time. On the other hand, the two birds can strongly bond (even same sex) and become a couple and want little to do with the people in the family. And then there are ones that fall in the middle, where they essentially ignore each other, but that means you need to provide social time and enrichment to two birds. The question is are you prepared and ready to accept any of those 3 possible outcomes?
As a bird home... we have interesting experience. We often have a foster in our home too, so can share from quite a bit of different situations. But a great example is my macaw, Max. I also have a bare eye cockatoo, they both are bonded to me and wonderful with me, they have absolutely no interaction with the exception if one does a panic flock call to warn me the UPS or mail person is about the break in and kill me, the other will scream too. Otherwise they do not verbally respond to each other, literally they have no level of connection. Reality, when Ivory (BE2) is sitting with me and Max sees her snuggling or getting all the attention, he will come over to climb up and chase her off. Ivory is flighted, so if she does not leave on her own, she gets 'tossed' to fly over to one of the many bird stands we have in our living area. While generally they ignore each other, they have never shown real aggression towards each other, even when Max goes to chase Ivory, its more like a dog bark, or a kid yelling to go away, never an actual attack (tho we don't test that and let them directly interact). But, in that breath, something to note, while Max tolerates me having a BE2, he was absolutely irate when we had another blue and gold in the home. And even when he goes over to visit at the shelter with me, I've tried introducing him to a couple other macaws I love and he is extremely possessive and super aggressive, not just the go away, but full out needing to separate them because he tried to attack. When Johan was here in the home, Max bite me a few times after I gave attention to Johan (not vicious to draw blood, just enough to get his point across that he was a very angry jealous little boy and his Momma should not be playing with another blue and gold). So, we've learned that while I can have a cockatoo or any of the other non macaw fosters we've worked with over the years, absolutely no way in heck would Max accept me bringing home another macaw. So, that is a thought to keep in mind....
I personally have seen more people think their bird would do well with a companion only to realize that when they pick a human, most parrots prefer their person over other parrots. Many will tolerate other parrot's presence in the home, but out of the 14 birds we have in our home, the only birds that are 'companions' to another bird are Victoria's two green cheek conures (which have pair bonded and are not quite the people birds they were before deciding they were a couple); the cockatiels (two are sisters that Victoria handraised, so they are very bonded to each other but still seem to see Victoria as mom) and then my little group of misfit budgies (they are not hand tame budgies, they live in a small group so the point was that they had a small friendly group).
Anyway, I've babbled on.... from both sides of the fence, the question really is - do you want another bird and do you have the time to commit to having another 'child'?
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Apparently his feathers were very grubby and he had no tail from being in a such a small cage. He's currently molting and in much better condition after being given vegetables and fruit and vitamins and regular bathing. The person he is currently with said they would like to keep him but their Macaw doesn't agree!
He definitely deserves it.
