Hundreds of black waterbirds of the same species had arrived a few days ago taking possession of the harbour of Arona. This had evidently caused upheaval in our large colony of small lake gulls which usually share these waters only with swans and ducks. No high-pitched screeching sounds begging for bread these last days. Only some silent trials of fly formations diving onto the compact group of the invaders. This very afternoon, on the third and last day of their stay, the black waterbirds had moved towards the middle of the lake between Arona and Angera, forming an even more compact group than they had done before. Then, while I was walking along the lake, looking at these waterbirds, a large number of lake gulls suddenly arrived and positioned themselves on the long wall and on the pavement of the lake front. One next to the other. There were about sixty of them staring towards the waterbirds, as in this photo. No sound to be heard. A few lake gulls flew into the direction of the black waterbirds landing in the water in front of them but remaining at a safe distance. Then, about ten waterbirds made the same sort of move towards the lake gulls. A group of lake gulls suddenly flew from one of the lake front trees and landed behind the group of waterbirds and moved nervously backwards and forwards. It was fascinating to see these silent preparations for what looked like to become a territory battle. Then, suddenly one of the waterbirds flew up from the water and was in a few seconds followed by all the other ones and in their turn by all the lake gulls which seemed to accompany them out of sight. After a few minutes I saw them returning to their usual dominion: Arona's harbour. Intense moments indeed.