Barn swallows to shoot or not to shoot

I put barn swallows, pigeons, squirrels, etc in the same group. If they are messing up my house or garage, they will be shot on sight. Nothing is worst than going into an area to work or get something and critters have been in there and messing everything up. I did a pretty good job of getting rid of the squirrels around my house. They got in the attic and made a mess. I have a few coming back now but will take care of them soon. The way you describe your barn, I would order a new tin of pellets and have a couple of trash bags ready.
 
You could look at it as population control. ie, assuming they have no natural predators, what limits them from reproducing to excess? Usually food supply and disease would be other natural controls.

Some population reduction may be beneficial for you and them.

This also raises a question about hunting based on beauty vs utility. eg, deer, raccoons, rabbits, etc are cute but can be very destructive. Spiders, snakes, etc don't have the cute factor, but they're very beneficial. At least to farmers, gardeners, etc.