Hmmm, nine thousand species of birds on Earth, several thousand mammals, a thousand or so reptiles and amphibians, hundreds of thousands of insects and other arthropods. He builds are ark one fifth of the biblical size, and he can only get four species on board.
Well, I'm convinced!
Your numbers are actually a little low: as of 2004 there are around 8,163 reptilian species, 4,629 known mammalian species, 5,699 Amphibian species, and 10,000 species of birds.
LOL!