Finally it was evident that there were four baby swallows after all.
Their fluffy heads were showing above the nest most of the time: eyes still closed, white-lipped beaks shut tight until a parent appeared.
They look quite comical; I suspect because they resemble the old blackface makeup of the Al Jolson era.
Then they snap their beaks open and show the yellow-orange interior for a long period, blindly hoping food will be placed in there.
The adult’s beak is black-rimmed, so it will be interesting to see just when the colour changes.
As the parent opened its own beak, I saw that the inside of its mouth is also orange, which I hadn’t realised.
Still no sound from the babies, but the parents chatter a lot, so I guess they’re silently learning, taking it in as babies do.