Article about something I already posted about: the study done on grays and B&Gs that found that grays help one another, even when they are strangers. The reason why I post this even though we already know about this is that this article cites a possible reason why the grays did it and the macaws did not: namely, that macaws evolved to live in small, close family groups while grays flocks are very large. See? Always go back to the way they evolved to live in the wild and you will find the right answer to your question!
https://www.psychologytoday.com/za/blog ... -tolerance