> Look again. The bird's head does not move backward at all, only
> forward.

I'll look closer if and when it returns. The stabilising of the gaze I can grok: I've seen that with chickens and pigeons, and it's related to the "spotting" done by a spinning ballerina who doesn't want to get giddy. But I could have sworn our magpies exaggerate the fore-and-back movement.