While researching some accounts reffering to the Washington Island Gadwall (Mareca strepera ssp. couesi Streets), I stumbled accros a footnote that made me wonder … a bit at least.:
“The native birds of Tahiti are in a sad state; the Porphyrio is extinct, as is the small grey, Thrush-like Omaomao [Tahiti Reed-Warbler (Acrocephalus caffer (Sparrman))], famous for its beautiful song, and the magnificent large Fruit Pigeon [Polynesian Imperial-Pigeon (Ducula aurorae (Peale))], of which a few existed as late as 1920.” 
Well, aside the fact that the name “Omaomao” is rather applied to the Garrett’s Reed-Warbler (Acrocephalus musae ssp. garretti (Holyoak & Thibault)), the Tahiti Reed-Warbler is still alive.
What amazes me is that the author mentiones the term “Porphyrio” in a absolutely casual way, and this certain author, Charles Nordhoff, knew what a Porphyrio is, he kept six New Zealand Swamphens (Porphyrio melanotus (Temminck)) in the garden of his house while living on the island of Tahiti.
There is furthermore a painting by Paul Gaugin, made in 1897 during a stay on Tahiti, it is called “Vairumati” (see below) and shows a female islander sitting on a chair and to her left a strange-looking white bird that very much reminds on a swamphen.
I personally do not think that Gaugin painted a real bird here because the same bird appears in several of his paintings, always in the same pose, differing only in the coloration.
It nevertheless is almost certain that a swamphen species once inhabited the island of Tahiti, and that additional species inhabited all of the other Society islands, however, the only true evidence for that assumption are the subfossil remains of McNab’s Swamphen (Porphyrio mcnabi Kirchman & Steadman) found on the island of Huahine.
I only somehow doubt that this Tahiti Swamphen disappeared only around the 1940s … but, who knows.
 Charles Nordhoff: Notes on the birds of Tahiti. The Avicultural Magazine ser. 5. 8(5): 119-120. 1943