Here's a cute little video just released by Irena Schulz of Bird Lovers Only (of Snowball, the dancing cockatoo fame). I don't know about her bite strength information, though. She says that a Greenwing macaw has a bite strength of 2,000 psi, and that they can snap a broomstick in half. I actually have a scene like that in Little Birdies!, so I did a bit of research there. As far as I know, 2,000 psi is crocodile and large snapping turtle territory, the only species I know of that can actually snap a broomstick with one bite. I believe macaws were in the 350-to-500 psi range, plenty strong enough to crush a gold ring, in Irena's case. Either way, the beak demands respect!