ben wrote:
One of the toilets in the house has an intermittent issue with air
bubbles.

Occasionally, when just sitting there unused, a single bubble of air
will 'blurp' as it reaches the water surface in the bowl. It might
happen once or twice in a day, or as many as ten times (possibly
more). The toilet has zero problems as far as function go.

I think we first noticed this last year but it went away after a
while. It returned a couple months ago.

I've read that a clogged waste vent could cause this. I've looked in
them (from the roof) an don't see any blockage. The other toilets in
the house don't have this problem either.

ideas?

It's a toilet gremlin. The creatures don't usually bother humans,
they may eat the occasional dog or cat that might drink from the
toilet but any good exterminator can usually get rid of them.

TDD