I have a pair of swallows who nest in my carport in the same spot every year. A previous tenant had put levelor blinds up there (why?) and I took them down. the birds nested on the rail of it but this year they managed to stick their nest to the wall using only mud.
I saw the mom and dad perched on the handlebars of my spin bikes and thought it an unusual behavior for them so I went out to look.

The mud didn't hold. The nest was on the ground, five babies had been knocked out of it but were still clustered together in nest form! I picked them up and arranged them back in the nest but still didn't know where to put it.
In a burst of ingenuity I knew how to get it back pretty close to where it was. This involved a snow shovel and a stepladder, I am the Maguyver of the avian world.
So far, everyone is living happily ever after.