New Zealand lacked mammalian land predators for millions of years, and was a marvel of biodiversity up until the arrival of man, who introduced rats and other new species. Stephens Island lies between the two big islands of New Zealand, and became a refuge for species that had been hunted to extinction everywhere else. Then humans moved to Stephens Island in 1894 to operate a lighthouse. They were three lighthouse keepers and their families, including David Lyall and his cat Tibbles.
Shortly after David Lyall took position as the assistant lighthouse keeper at Stephens Island, Tibbles started bringing him such presents. Although Lyall had been on the island for only a short time, he could put a name to most of the birds Tibbles brought him, except for one peculiar specimen. This bird was small, olive on the back, pale on the breast, with body feathers edged with brown. It had a narrow whitish yellow streak above the eye, short wings, and a long, straight bill. Lyall had never seen this bird before, and for that matter, no biologists ever had. Sensing that he was on the verge of a new discovery, Lyall sat down one evening and by the light of a paraffin lantern, started to prepare the specimens. He sent a number of them to some of the most renowned ornithologists of the time, including Walter Rothschild, Walter Buller, and H. H. Travers.
Walter Buller immediately recognized it as distinct species and began preparing a scientific description to be published in an upcoming journal. Walter Rothschild, a British banker and zoologist, acquired several specimens from Lyall for a handsome price. It was Rothschild who suggested the scientific name Traversia lyalli in honor of David Lyall, the discoverer, and naturalist H. H. Travers, who helped him procure the specimens.
Within a year, Tibbles no longer brought in Traversia lyalli, or the Stephens Island wren, as her prey. The bird couldn't be found alive, either. Although there have been a few sightings in later years, the wren went extinct. Every existing specimen of the species was caught and killed by Tibbles. Read the story of the wren that is no more at Amusing Planet. We only know about it because Lyall was an amateur ornithologist. Imagine how many other species humans have wiped from existance without us ever knowing. -via Strange Company
While the title of the linked article implies that one cat hunted the wren to extinction, Wikipedia adds more details to the story. When the lighthouse keepers and their families moved to the island in, it is believed that more than one cat was brought along. At least one cat was pregnant and escaped into the wild. Within a year, the island had a growing population of feral cats. By 1897, shotguns were brought in to exterminate the cats, and by 1925, there were no more cats on Stephens Island.