…corvids and psittacines [have cognitive powers superior to most apes]. That’s really the culmination of studies beginning in the
1970’s (most famously Irene Pepperberg’s studies on grey parrots and Herrnstein’s on pigeons) and is something that has only just become, I think, mainstream biological thought around now: but it rests on as firm experimental obsrvation as any studies of primates (certainly of orangutans). Corvids and psittacines simply outperform even chimpanzees in many ways. …On the other hand, the selective pressures on birds are pretty nasty. Their biochemistry seems a hell of a lot better than ours (witness the longevity of these things). So perhaps it’s an alternate route to great intelligence: if you know that say four out of five young are going to die anyway you can take the risk of 80% of the offspring being quickly developed morons. I don’t know enough about the field to validate that but I think it’s an interesting idea.