This is a study done on corvids but it could have been done with parrots and they would have gotten the same results. And they found that it is their highly social life that is the driven factor behind generosity (remember the study done with African grays?) which tells, once more, how important it is for a parrot to have companions of their own or similar species.
https://www.sciencedaily.com/releases/2 ... 112557.htm