5 eggs and then 5 chicks in a tiny mud daubed nest.
Each day I took a picture, and each picture showed the rapidly growing brood, and the rapidly diminishing space in that nest. I observed that the babies would force their way through the crowd to the top, then position their derriere over the edge of the nest, and – bombs away – on the floor below. Soon there was a big pile of guano littering our deck under the nest.
When they had left the nest, and I took it down, there was not one dropping inside.
I do not recommend letting barn swallows build at your home. In addition to the mess, they are extremely aggressive, and will attack any and all interlopers on their territory. Not only that, they will also return the next year and insist on rebuilding on the ancestral site. It takes diligence and a broom to discourage them.
Bluebirds have a different method. For several years we have had the privilege of having bluebird broods in a birdhouse at the edge of our lawn. Lots of pictures to show for it, and they return each year. Currently, they are raising their second brood.
For some time I watched the male go to the house, poke his head inside, and then fly away with a small white package in his beak. When I cautiously opened the front of the house I found that the babies poop right on the front edge of the nest, just inside the entrance hole. The male picks it up, and carries it away, and not just anywhere, but far away.
When the brood leaves, you will find not one dropping in that nest.
Now, on the other side of this story are the tree swallows. Again, a nest built inside a bird house, and the nest is the epitome of perfection. It is lined with feathers all neatly interwoven to provide a cozy and comfortable place to raise the young.
However, their sanitary proceedures seem to be lacking, for when they finally leave the nest and I take it out of the box, it is brimming with droppings.
I guess birds really are a lot like people!