The pictures were taken through the windows around our front door (hence the awkward reflections), but there are at least two and perhaps three babies in the nest. Barn swallows feed by catching insects mid-air, so mom and dad are busy flitting around looking for bugs. Barn swallows are very fast and maneuverable fliers!
There are lots more barn swallows than our pair flitting about, which makes me wonder if there are other nests.
Are you observing nature at work around your house? Are you tickled pink (as we are), or do you find nature's activities inconvenient or destructive? I admit I'm not thrilled with the wasps flying around and want to search out their nests and spray them first chance, but then I wonder if the poison will be picked up by birds eating the wasps. Unintended consequences suck.