Update . . .

. . . on our House Martins

The nest has been much improved and has a side entrance, which they are using at the moment to fly in and out of. This is constant so we have to assume they are feeding young. They are so fast, I had to watch for a long time before I managed one flight photo (extra).

We realise now that, although our windows are modern and unsuitable for nests, they all have a sort of ledge at the top. We have no idea whether this has a purpose or is just a design feature, but it is perfect for the Martins.