I maybe wrong, need to check the book which I have to confirm, but I thought the bird (cormorants?) shooting with a rifle was with defective 6.5x54 ammo.

Most of the famous old timer hunters wrote more about the animals they shot and didn't always note what rifle/cartridge they were using in each case. John (Pondoro) Taylor was one of the few who specifically noted in his narratives what he was using to take each game animal.