Swallows nesting

I had been looking for where the swallows might have been nesting, given they were absent from their usual position in the wood shed. Finally the location of their new nest was revealed as being within the old aviary. Once used for breeding budgerigars, it has been unused for some time. That said, the swallows have worked out an access point, swooping down and entering between the roof post and iron sheeting. How they do this at the speed they do, navigating the tiny space available is beyond me. So after watching them come and go for a day I decided to explore further as their continued activity suggested that they were busy for a reason.....and what a reason. Perched just above head height, on a ledge inside the doorway is a beautiful little mud nest. Lined with feathers, what I originally thought to be a nest ready for eggs, was in fact filled tight with baby birds. I had to drag a rock in to stand on so that I could look down into the nest itself, but this improved view revealed that what I originally thought was a feathered lining was the babies themselves. They are wedged in so tight I have been unable to count them as yet....but am guessing perhaps three babies. They have an inbuilt mechanism to sit quietly so that predators are unaware of their location. So they sat, eyes closed, barely moving, snug in their little nest, protected from the wind. I imagine this changes as soon as a parent comes back with food....then it will be on, all of them clamouring for food. Incredible to think that these migratory birds will soon be headed off on a long distance trek.