For most of us barn swallows are a bit of a nuisance, they seem to build their nests at the most awkward spots... like right over your doorway on your deck.  A zoo in Seattle really like them though.I happen to find them pretty funny, as long as they're not making a complete mess.  They are pretty brave as they swoop at your head or the cat walking accross the yard.  And let's face it, they're busy birds, it's pretty amazing how they build their nests.

The Woodland Park Zoo in Seattle found a barn swallow bird nest, and instead of knocking it over, they put up a camera, watch it here.

http://zoo.org/animalcam#.UdnrAvnrymg