 The invisible rail , Wallace 's rail , or drummer rail ( Habroptila <unk> ) is a large flightless rail that is endemic to the island of Halmahera in North <unk> , Indonesia , where it inhabits impenetrable sago swamps adjacent to forests . Its plumage is predominantly dark slate @-@ grey , and the bare skin around its eyes , the long , thick bill , and the legs are all bright red . Its call is a low drumming sound which is accompanied by wing @-@ beating . The difficulty of seeing this shy bird in its dense habitat means that information on its behaviour is limited . 
