Great northern divers are now to be seen along the British coasts — almost anywhere — but mostly around Scotland. They will sometimes come close inshore, and into harbours such as Poole Harbour, in Dorset, where several have recently been seen from boats. They are magnificent birds, especially in summer, when they have a chequered, black-and-white back and a green gloss on the head. In winter they are dark grey and white, yet they are still handsome as they swim past with their long, thick neck held erect, topped by their massive head and a long, sharp beak.
They will come quite close to people, even being inquisitive about them, and are well worth watching because they perform many tricks. Sometimes they swim around with their head under water as they look for fish below them. If they are uneasy they will float for a while with only their head showing above water as they watch for danger. When they dive you never know where they will come up because they can stay under water searching for fish for as long as two minutes.
They also come inland occasionally to reservoirs and very large lakes. They hardly ever visit small waters because they need a lot of space to get under wing when they fly up. They are very long birds in the air, with their neck out and feet projecting behind them.
Andrew Moon, a contributor to British Birds magazine, reports an unusual experience with one last January. There was a great northern diver and a flock of 25 tufted ducks and goldeneyes near it on the King George VI Reservoir in Surrey. The diver dived, then suddenly came up in the middle of the flock, bent its neck into an aggressive “S” shape and chased all the ducks away.
This individual had wintered on this and other southwest London reservoirs in the three previous years, and Moon wondered if it had come to regard these reservoirs as its winter territory.