Last week we saw a Great Northern Diver (Gavia immer) sneak up on a Red-breasted Merganser with its chicks several meters from the shore. The Diver behaved like a sheepdog and prevented the group from going on the lake. It dived towards them and forced them up to the shore repeatedly.
The Merganser was on constant look out both on and under the water surface. Although the Diver’s mate and chick were in about 1 km distance the diver thought the Merganser and its chicks were a threat which should be kept at bay.
The Great Northern Diver is known for its fierce treatment of intruders that venture into its territory. It is known to dive under other birds wounding them with its spear-shaped bill. People have witnessed them killing both duck and geese chicks this way and even adult birds, such as the Long-tailed Duck.