SHILLCOCK NH (1991) Short contributions: Great Black-backed Gull Larus marinus attacks Goosander Mergus merganser. LIMOSA 64 (1): 26-26.

In February 1984, at Bovenwater in Zuidelijk Flevoland, a Great Black-backed Gull Larus marinus attacked two fighting Goosanders Mergus merganser. One Goosander was attacked without success; it escaped by flying. The other bird was attacked violently, grabbed by its head an almost pushed under water. This bird freed itself and escaped by diving. It is suggested that these Goosanders were attacked because they were solitary.

[free pdf] [dutch summary]