Wiktionary
great northern diver
n. (context UK Ireland English) A large member of the diver family, ''Gavia immer,'' commonly breeding in North America, where it is known as the as common loon.
Usage examples of "great northern diver".
On their way out to the great mere, where an osprey had been seen that summer and where hard winter might bring down the odd great northern diver, they saw Captain Griffiths riding along his former track and peering about.