Mice brought to a remote south Atlantic island by sailors in the 19th century are threatening seabirds including the critically endangered Tristan albatross, a British charity said on Monday.

The Royal Society for the Protection of Birds said the rodents had proliferated on uninhabited Gough Island, part of a British overseas territory, and were killing two million birds every year.

"We knew there were large numbers of chicks and eggs being eaten each year but the actual number being taken by the mice is just staggering," Alex Bond, a researcher from the Natural History Museum in London, said.

The predatory mice had evolved to become "two or three times larger" than the average house mouse and attack in groups, eating away at the flesh of chicks that suffer for days before the open wounds lead to their deaths, the society said.

The Royal Society for the Protection of Birds and Tristan da Cunha government are teaming up with international partners to eradicate mice from Gough Island in 2020, using two helicopters laden with poisonous pellets.

"Restoring the island to a more natural state will prevent the deaths of millions of seabirds," said John Kelly, the society’s manager for the Gough Island mouse eradication programme. AFP