Bats in Barrel Tile Roofs in Riverview, FL
The void is part of the roof
Barrel and Spanish tile is everywhere in the subdivisions built here since 2000, and the shape of the tile leaves an open void at the end of every course. That void is dry, it holds warmth overnight and it sits above the wall line out of reach of anything on the ground. For a small colony it is close to purpose built, and the attic can stay completely sealed while it is occupied.
Because the gap is how the roof works rather than a defect in it, it never shows up as damage. What is visible from outside is staining down an exterior wall below the roof edge. Checking the attic finds nothing, because the colony is in the tile rather than the roof space.
Closing tile without wrecking the roof
The tile ends have to be blocked while the roof keeps breathing and draining. Mortar or spray foam pushed into the voids traps moisture against the underlayment and buys a roof problem in place of a bat problem, so purpose made tile closures go in instead.
On a roof still inside its manufacturer warranty the method is not a detail. Work goes course by course, brittle tile gets loaded carefully because it cracks under careless foot traffic, and the closures used are ones a roofer will not object to when the next inspection comes round.