These images are from a recent trip into Geneva. All the birds around l’Île Rousseau are usually pretty mellow around each other. However I have noticed that the mergansers can be a little more irritable than the others, and on this particular day they were outright aggressive…perhaps pickings had been slim that day. In any case, on one occasion a merganser had taken it out on a mute swan, actually ending up on the swan’s back! In these images, it’s just an altercation between mergansers over a piece of bread.
If you enlarge the second image you can see the pursuing merganser’s eye amid the spray.