Size and Weight:
About the Stephens Island Wren:
Tens of thousands of years ago, the arrival of aboriginal humans on New Zealand drove some indigenous species to extinction--and a few that didn't go extinct managed to relocate to Stephens Island, a small island about two miles off the New Zealand coast. One of these fortunate creatures was the Stephens Island Wren, the only living specimens of which were discovered by English settlers, who landed on Stephens Island in 1892 with the intention of building a lighthouse. Otherwise unremarkable looking, the mouse-sized Stephens Island wren was noteworthy for being completely flightless, an adaptation usually seen in larger birds like penguins and ostriches.
You can probably guess what happened next. At some point during the construction of the lighthouse, a pregnant cat (brought all the way over the Pacific from England) managed to make its way onto the island, and it and its brood quickly hunted the small, defenseless Stephens Island Wren to extinction. In the course of the carnage, one of the lighthouse keepers, David Lyall, managed to collect some preserved specimens, which he sold to collectors for substantial sums of money; today you can find the Stephens Island Wren on display in various museums (the American Museum of Natural History in New York has four in its vast collection).