I've gotten a number of responses to the humorous comment I added to my post on the ibis yesterday.
I thought everyone would get the absurd image of an ibis chewing its way through wire to be obviously ludicrous.
The 'gap' seems to come from shadows along the ridges along the upper edge of the mandible, especially the thickest ones running along the tomia [the top edge of the lower mandible and the lower edge of the upper mandible]. I think the shadows are accentuated if the bird is heat-regulating, with its bill slightly open.
Many photos of ibis's bills show this effect.
The excellent photo that John Sterling posted this morning shows this effect on the bird in Baker.
Personally, I see no reason to say that this bird is not wild.