 The invisible rail inhabits the dense , spiky sago swamps of Halmahera , particularly where forest <unk> the <unk> areas . Claims that the rail occurs in <unk> @-@ <unk> 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 <unk> <unk> , wrote of the sago swamp habitat in the 1930s : 
