The Alaotra grebe, a kind of duck that lived only in Madagascar, has been officially declared extinct.
From The Telegraph:
The grebe was wiped out by habitat destruction, by the introduction of a carnivorous fish called the snakehead murrel and by nylon gill-nets which accidentally caught and drowned many birds.
“No hope now remains for this species. It is another example of how human actions can have unforeseen consequences,” said Leon Bennun, director of science at BirdLife International.
Image source: telegraph.co.uk