What happened next was something quite different. The male who as I have said previously is very excitable, reacted in an aggressive way to another dipper that flew through the territory. This incensed "our" breeding male who flew the "fighter-plane" patterns chasing around, swooping in circles over the water and then landing on one of his favourite boulders calling with a bubbling musical call, quite unlike the normal single syllable flight call, a mixture of call and song. He repeated this behaviour for quite some time. The strangers presence made them very wary and when they then came near to the nest a while later they were very suspicious and wouldn't approach, at this point a Wessex Helicopter flew low over the woods and this was just too much for the birds who were definitely spooked and left with some haste.