Bats

Three pastors were discussing the problems they had been experiencing with bats in their church lofts.

The first said "I introduced a dozen cats, but that didn't seem to work. The bats are still there".

The second said "I had the place fumigated, but even that didn't work. It's still infested with bats".

The third said "I baptised all mine and made them members of the church.

Spoiler:

I haven't seen one of them back since!"