Every year, the Welcome Swallows come back from their summer somewhere on the mainland and put their nest back into shape, using mud taken from the dam one beakfull at a time, ready to raise another batch of youngsters.
It is nearly always the same nest. A few years ago they switched to a new one a few metres away from the original, and have used that one since.
Whether it is always the same pair, we don’t know. They seem to know their way around the place, and keep to the same habits. Possibly when one partner dies, another one takes its place; we have no way to tell.