In reply to Bottom Clinger:
There was one thing that really made me think about their intelligence.
I took a grape out as he'd been calling for one and was going to put it on a low railing beside the lawn. By the time I brought it out he'd hopped off on to the grass.
I put it down on the lawn and put my finger down to it to emphasise that it was there for him. No reaction apart from a stare.
After a while I cottoned on that he might be affected by the fact that it was in full view of any other birds in the area so I picked up the grape and put it down on his side of a large piece of wood so that it was hidden from view in many directions but he could see it.
He began a very slow zigzag back and forth with pretences of looking under leaves but with a resultant vector taking him ever closer to the grape though he was determinedly pretending not to be seeing it. It was almost as if he was tacking towards it.
Finally, when he got within a foot or so of it he looked around and then dived for it before flying off loudly chittering with excitement.
Post edited at 12:32