Nothing appears to have been done to it. The head and tail are not glued on - I checked with my gem microscope, what superficially look like seam lines aren't. No glue. The glass, not surprisingly, isn't actually black, but shows dark reddish brown at small fracture points. I tested one of these patches with a hot point to see if it was glue or resin and would melt, it simply fractured from the heat stress and popped off leaving a typical conchoidal glass fracture below.

The white material in the swirls looks to me like corroded glass and not like plaster, if that's what the other possible candidate is.

Anything else incriminating I should be looking for?

I still think its resemblance to a bird is merely a nice coincidence.