The eldest youngster quickly jumped up onto the rim of the nest tub & took up a defensive posture - ive noticed that on taking up this stance the birds initially close their eyes for a short spell - as if to confuse any would be predators.
A closer view
After a few moments they settled down
Side on view - at this point, one of the adults flew into view - the youngster seemed to forget about his peace being interupted, a good time to head off & leave them to it.
Female sitting on rim of nest.