Saturday scenes: what's that in the birdbath?

Among the odd artifacts along city streets, some of the oddest are various figures in birdbaths. Okay, perhaps this is meant to be a half-shell, but I am sure when there is rain, it functions as a birdbath.

These two are undoubtedly birdbaths, however different their occupants.

This one is just weird.

While this one is almost dainty by comparison, if you like that sort of thing.

The birdbath as planter seems just prosaic.

All observed which Walking San Francisco.