There were a group of about four Welcome Swallows flying over the river to the shore on the far side from me. They would land on the far bank, then take-off, often disappearing for a while before returning. On looking at the photographs closely I realised they were gathering mud, probably for nest building. I did not get a chance to check but I noted they were generally flying off in the direction of the house-sized water pumping facility, so I wondered if they were building nests there.