Swallow entering its nest

In a friend's garden today, I found a birdhouse with swallow tenants. That is new to me. In my old Sweden I have never seen swallows nesting in birdhouses. This one obviously was sitting on eggs.  It went in and stayed for a very long time, and then went out for a while, probably feeding itself. And it is important for the eggs that they can cool off for a short while. That supports the breathing of the eggs. Here the bird is returning from a feeding trip, It took great patience to get the shot. I provide two extra photos, to show how it enters the house.