When I arrived at 9.30 this morning, I tried not to disturb the bird that I could see frantically working inside the, as yet, hollow nest opposite. I was successful and slipped in unnoticed and she carried on untroubled. The male came along just a few minutes later and started to sing before he joined her in the nest. I made a guess that he had just arrived at the nest site for the first time as he didn't sing like that for the next three hours, but more about that at the end of this piece. At the moment the nest is starting to look more rounded and it seems to be fully lined now, however there are still days and days of building to be done. I have read that nest building can take as long as 3 weeks, if so this would put us on around the same time frame as last year when the first egg was laid on the 26th March. There was lots of noisy chattering when he joined her with that churring, bubbling sound. This noise is quite audible above the noise of tumbling water and seems to be associated with nest building. I said previously that this was a greeting but I am certain now that it is a sound used whenever they enter the nest, perhaps later when chicks are in the nest it is a greeting to them? It was interesting to note that the male is more vocal and made the noise even when he entered the nest alone and while the female was absent. It certainly drew my attention to the nest which is odd because in every other respect they are very cautious. Nest building went on for just about three hours, both birds fetching and carrying material and they would take it in turns to be up in the nest. Sometimes one bird would arrive at the nest and the other would immediately depart but mostly the female would wait on rocks beneath the nest for her mate to finish before she flew up. Every beak full of moss was thoroughly dunked in the river and completely soaked before it was used. This may make it easier to manipulate in to the existing structure. I watched this wetting of nesting material continually last year so it is an obvious ritual that is always carried out. Building material was mainly moss, either gathered from the dry bank or wet rocks. On two occasions, grasses and leaves were brought back. Both birds took part in building today but the male, at one point was seen to start feeding for 20 minutes or so before carrying on with building duties. I didn't see the female take this kind of feeding break. At the end of the session there was a dramatic change in the demeanour of both birds which signalled an end to this particular part of their daily routine. The male had already left and gone down stream to patrol his territory. After a few minutes he came back and called musically. The female, with much excitement left the nest and started to dip and bob, which she hadn't done in the previous three hours. She responded to the males presence with wing fluttering and dipping and I thought that copulation might take place. They both hurriedly departed together and in the same direction upstream presumably to feed in the area where they seem to spend the later part of the day, 300 hundred meters or more from the nest. It was more than obvious that they had stopped for the day as their behaviour was so dramatically different from the previous three hours.