One other avian cognition story. My ex-gf had this huge, very bright cockatoo, who preferred to drink from bottles or cans (because that's what humans did) but would drink from an open container in his cage if he didn't have a bottle handy. It was a fairly deep steel bowl, and he liked to stick his head in there and screech because it sounded weird. I was in there playing with him and whistled, then put my head in a bucket and whistled, and he cackled, and did the same thing. Then he froze and thought -- I could tell -- and screeched a weird distorted sound, that was his imitation of what he heard when he screeched with his head in the bowl. Then he looked at me, put his head in the bowl, and screeched the distorted sound and listened to that sound, tried imitating that, and so forth, for a few minutes before he lost interest. But watching him make the cause-and-effect realization and start experimenting with it, was a seriously eerie experience, a moment when I realized what his brain was capable of comprehending, albeit briefly.