[E. Pluribus Unum]

The main problem with birds is the grit some species ingest to mechanically grind their food. It also grinds any lead they might ingest, breaking it down into smaller, more soluble pieces.

Fish don't have an actively grinding alimentary canal. It's just sort of a tube.

[1010RD]

OK, so it get’s ground down smaller, but why is it more soluble outside of an acidic environment?

Is the stomach acid in the birds sufficient to cause it to go to salt?