The invisible rail inhabits the dense , spiky sago swamps of Halmahera , particularly where forest adjoins the boggy areas . Claims that the rail occurs in alang @-@ alang grass are thought to have arisen from confusion with the pale @-@ vented bush @-@ hen . German ornithologist Gerd Heinrich , who prepared for his Halmahera trip by rolling in stinging nettles , wrote of the sago swamp habitat in the 1930s :