 The invisible rail is superficially similar to the purple swamphen , <unk> <unk> , which has recently been found in Halmahera , but that species is larger , with a short , thick red bill and a red forehead shield ; it also has purple underparts and a white undertail . The invisible rail is different from the <unk> rail , <unk> <unk> , in that it is larger and lacks the barred plumage of that species ; there is no overlap between the ranges of the two species . 
