Alright, sounds like there is no clear/official answer that I missed, then! I like the archaeology idea- that he doesn't have all the bird-themed stuff necessarily because he's from there, but because he was investigating it. But, indeed, it's all guesswork.
Of course, only now do I remember my third question, a completeness question not related to plot.
In the "secret cave passage" section of Open Water (above the statue leading towards Mithalas that ends the demo, west and down from the Kelp Forest turtle), there is a black hemispherical creature that walks in circles on a rock formation. I never found anything I could do with or to it, in any form. Is it just decorative, or does it have a tiny little secret purpose?