[KirinChris]

We only moved to our property late September and are just now in the process of cleaning up and painting the stables.

We’ve noticed a couple of swallow nests in one of them. No idea how recently it was used but it seems to be in good condition.

Should we leave it as is? Do they come back to a nest or do other birds use it? Or will they build fresh ones?

[doganjo]

Each year, about 44 percent of all barn swallows will return to nest in the same area they nested the previous year.

If the older birds decide to renovate their old nest, they begin by throwing out and replacing old nesting material and adding more mud around the nest's rim. So it can be quite messy!

I would leave them meantime but if they aren't used in spring take them down

[Penninehillbilly]

Ours always use one of the nests already there, not sure how much mess they make, so much of husband's junk over that side of the barn, I wouldn't see it anyway. .
They are right up in the top, so we can't check them, but one year I don't think the last lot of eggs hatched, or didnt survive, the following year they used a different nest, but the year after, they were in it again.