The massacre is taking place on Gough Island (map), a British territory almost smack-dab in between the tips of South America and South Africa. The only humans living on the island belong to a small team running a weather station.

Gough Island has long been recognized as an important seabird colony, since it hosts roughly ten million birds of more than 20 species. The island is also thought to be the only breeding ground for the Atlantic petrel—2 million breeding pairs produce 1.6 million chicks a year.

The new study, though, reveals that the petrel chicks are in constant danger from house mice, which have grown to supersize proportions since being introduced to the island 150 years ago.

(Related: "Viking Invaders