 The breeding habitat of the water rail is permanent wetland with still or slow @-@ moving fresh or brackish water and dense , tall vegetation , which may include common reed , <unk> , irises , bur @-@ reed or sedges . In coastal areas , sea rush is common in saltmarsh breeding sites , with sedges and bur @-@ reed dominant in somewhat less saline environments . A study in the Netherlands and Spain showed that the rush provided better concealment than the other maritime plants . As elsewhere , nests were constructed from the nearest available plants . Where it occurs , saw @-@ sedge provides good breeding habitat , its tall ( 1 @.@ 5 m ( 4 @.@ 9 ft ) ) dense structure providing good cover for the nesting rails . The preferred habitat is Phragmites reedbed with the plants standing in water , with a depth of 5 – 30 cm ( 2 @.@ 0 – 11 @.@ 8 in ) , muddy areas for feeding and a rich diversity of invertebrate species . Locations with nearby willows or shrubs are favoured above large areas of uniform habitat . In addition to natural fresh or marine marshes , this rail may use gravel or clay excavations and peat workings as long as there is suitable habitat with good cover . It may be found in rice paddies or on floating islands , and it occurs in Kashmir in flooded sugarcane fields . A Finnish study showed that the main factor influencing the distribution of water rails was the extent of vegetation cover , with the highest densities in the most vegetated areas ; the presence of other marshes nearby was also significant . However , factors such as temperature , rainfall , length of shore line and extent of peat , important for some other marsh birds , were not statistically relevant . The areas with the highest densities of the rail also had the greatest numbers of three species considered at risk in Finland , the great reed warbler , Eurasian bittern and marsh harrier . The northern limit of breeding seems to be determined by the transition from nutrient @-@ rich wetland to poorer , more acidic water . This leads to the replacement of common reed by a more open vegetation type dominated by marsh cinquefoil , which is unsuitable for the rails . 
