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The water rail, western water rail or European water rail ( Rallus aquaticus) is a bird of the Rallidae which breeds in well-vegetated across Europe, Asia and North Africa. Northern and eastern populations are bird migration, but this species is a permanent resident in the warmer parts of its breeding range. The adult is long, and, like other rails, has a body that is flattened laterally, allowing it easier passage through the it inhabits. It has mainly brown upperparts and blue-grey underparts, black barring on the flanks, long toes, a short tail and a long reddish bill. Immature birds are generally similar in appearance to the adults, but the blue-grey in the plumage is replaced by buff. The downy chicks are black, as with all rails. The former subspecies R. indicus has distinctive markings and a call that is very different from the pig-like squeal of the western races, and is now usually split as a separate species, the brown-cheeked rail.
The water rail breeds in reed beds and other marshy sites with tall, dense vegetation, building its nest a little above the water level from whatever plants are available nearby. The off-white, blotched eggs are avian incubation mainly by the female, and the precocial downy chicks hatch in 19–22 days. The female will defend her eggs and brood against intruders, or move them to another location if they are discovered. This species can breed after its first year, and it normally raises two clutches in each season. Water rails are omnivore, feeding mainly on invertebrates during summer and berries or plant stems towards winter. They are territorial even after breeding, and will aggressively defend feeding areas in winter.
These rails are vulnerable to flooding or freezing conditions, loss of habitat and predation by mammals and large birds. The introduced American mink has exterminated some island populations, but overall the species' huge range and large numbers mean that it is not considered to be threatened.
The former subspecies R. a. indicus has very different vocalisations from the water rail, and it was considered to be a separate species in early works. It was restored as a full species R. indicus, by Pamela Rasmussen in her Birds of South Asia (2005).
Her treatment has gained acceptance, and is followed in Birds of Malaysia and Singapore (2010). A 2010 study of molecular phylogeny further supported the possibility of specific status for R. indicus, which is estimated to have diverged from the Western forms around 534,000 years ago.
The water rail can readily be distinguished from most other reed bed rails by its white undertail and red bill; the latter is a little longer than the rest of the rail's head (55–58% of the total) and slightly down-curved. The somewhat similar slaty-breasted rail of tropical Asia has a stouter bill, a chestnut crown and white-spotted upperparts. Juvenile and freshly moulted water rails may show a buff undertail like spotted crake, but that species' plumage is spotted with white, and it has a much shorter, mainly yellowish bill. The range of the water rail does not overlap with that of any other Rallus species, but vagrants could be distinguished from their American relatives by the lack of rufous or chestnut on the closed wing. The larger African rail has unstreaked darker brown upperparts and brighter red legs and feet.
When researchers played recordings of the reed warbler at night to attract that species for trapping, they found water rails and other wetland birds were also grounded, despite a lack of suitable habitat, suggesting that the rails and other nocturnal migrants recognised the warbler's song and associated it with the marshy habitat in which it is usually found.
The differences between the three other races appear to be clinal, and it is possible that they should all be merged into R. a. aquaticus.
The Icelandic population of water rail, R. a. hibernans, became extinct around 1965, as a result of loss of habitat through the draining of wetlands, and predation by the introduced American mink.
Prior to its extinction, at least some birds were present year-round on the island, relying on warm volcanic springs to survive through the coldest months, but this race was also found in winter in the Faroe Islands and Ireland, and on passage through the Outer Hebrides, suggesting that the Icelandic form was a partial migrant. The nominate subspecies, R. a. aquaticus is resident in the milder south and west of its range, but migrates south from areas that are subject to harsh winters. It winters within its breeding range, and also further south in North Africa, the Middle East and the Caspian Sea area. The peak migration period is September to October, with most birds returning to the breeding grounds from March to mid-April. A specimen of the nominate population labelled as "Balochistan" and collected by Richard Meinertzhagen is considered of doubtful provenance. R. a. korejewi is another partial migrant, with some of the population wintering from Iraq and eastern Saudi Arabia eastwards through Pakistan and northern India to western China.
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 Phragmites, Typha, irises, Sparganium or Carex. In coastal areas, Juncus maritimus 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, Cladium mariscus provides good breeding habitat, its tall () 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 , 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 Comarum palustre, which is unsuitable for the rails.
Occasionally, more unusual locations are used. One pair in Scotland nested in the open by the side of a road, and when an English nature reserve installed nest boxes for bearded reedling (reed "" with a wooden floor), rails nested both in the boxes and under the wooden floor, in the latter case sometimes with the tits in residence above. Although mainly a lowland species, the water rail breeds at in the Alps and in Armenia. An Italian study suggested that reed bed birds need a minimum area of wetland for breeding, which for the water rail is about , although the highest densities are in marshes of or more.
On migration and in winter, a wider range of wet habitats may be used, including flooded thickets or bracken. Freezing condition may force birds into more open locations such as ditches, rubbish dumps and gardens, or even out onto exposed ice. A Welsh study suggested that individual winter territories overlap, with each bird using a significant proportion of the reed bed. After site desertion in freezing weather, birds return to their former range. A density of 14 birds per hectare (6.6 per acre) was recorded. Birds wintering in Iceland rely on warm geothermal streams, and may access streams through tunnels under the snow. When not feeding, they may shelter in holes and crevices in the solidified lava. This species sometimes wanders well outside its normal range and vagrants have been found in the Azores, Madeira, Mauritania, the Arctic, Greenland, Malaysia and Vietnam.
This species defends its breeding and wintering territories. Birds will charge each other with neck outstretched when breeding, sometimes both members of a pair attacking together. Large strongly-marked males are dominant in winter, when the direct aggression is replaced by sharming while standing upright on tip-toe, head jerking and bill thrusting.
The nest is made from whatever wetland vegetation is available and built mostly by the male, usually in a single day. It is raised or more above the level of the marsh, and is sometimes constructed on clumps of roots, tree stumps or similar support. It may be built up higher if the marsh waters start to rise. The nest is across and about high. It is well hidden and approached by narrow tracks.
The typical clutch is 6–11 eggs across most of the range, but appears to be smaller (5–8) in Kashmir at around altitude. Laying dates vary with location, from late March in Western Europe and North Africa, to late May in Kashmir and June in Iceland. The clutch size may be smaller early or late in the breeding season. The breeding season can be extended by replacement and second clutches. The eggs are blunt and oval, smooth and slightly glossy; the colour varies from off-white to pink-buff, with reddish-brown blotches mainly at the broader end that sometimes merging into a single patch. Variation in egg size across the four subspecies is much less than the differences between individual eggs; the average size of the eggs of the nominate subspecies, , is therefore typical for the species as a whole. The eggs weigh about , of which 7% is shell.
Both parents incubate the eggs, although the female takes the larger share of this duty. The eggs are incubated for 19–22 days to hatching, with at least 87% success. Food is brought to the nest by the other adult and passed to the sitting parent who feeds the chicks. The precocial, downy young leave the nest within two days of hatching but continue to be fed by their parents, although the chicks also find some of their own food after about five days. They are independent of their parents after 20–30 days and can fly when aged 7–9 weeks. If a nest appears to have been discovered, the female may carry the chicks or eggs one by one to another location; the eggs are carried in the bill, but small chicks may be tucked under the wing. Sitting birds may stay on the eggs even when approached closely, attack the intruder, or feign injury as a distraction. The water rail can breed after its first year, and it normally raises two broods.
Average survival after fledging has been estimated as between 17 and 20 months, with an annual survival rate slightly less than 50% per year for the first three years, and somewhat higher thereafter. The maximum recorded age is 8 years 10 months.
Water rails follow definite routes when feeding, frequently returning to good hunting areas. These rails are versatile and opportunist foragers. They will jump to take insects from plants, climb to find berries, or dislodge apples from trees so they can be eaten on the ground. They will kill birds by impaling or drowning them, particularly if the bird's ability to escape is restricted. They have been recorded as killing a European greenfinch and a king quail in an aviary, and small birds trapped in bird ringing' . One bird killed a twite caught with it in a Heligoland trap. They are also nest predators, particularly of small birds that nest in reeds such as the great reed warbler. Water rails may defend a winter feeding territory, although this is smaller than when breeding, with individuals perhaps less than apart; favoured sites may hold hundreds of birds. Aggressive behaviour outside the breeding season may extend to attacks on other marsh rails such as spotted crake and Baillon's crake.
Parasites include the sucking louse Nirmus cuspidiculus and Pediculus ralli, the tick Ixodes frontalis, and the Hippoboscidae Ornithomyia avicularia. The water rail can be infected by the avian influenza virus and the bacterium Borrelia burgdorferi, carried by Ixodes ticks, which is also a human pathogen causing Lyme disease. Three louse, Fulicoffula rallina, Pseudomenopon scopulacorne and Rallicola cuspidatus discovered on dead water rails in 2005 on the Faroe Islands were all species that had not been found on the archipelago previously. The Cyclocoelidae Ophthalmophagus nasciola was found in one rail's nasal sinus, and at least three species of feather mite have been detected on the plumage. The louse Philopterus ralli and the nematode Strongyloides avium have been found on the closely related brown-cheeked rail R. a. indicus.
Introduced predators are a threat to vulnerable island populations. In addition to the Local extinction of the Icelandic race, mink have been responsible for marked declines in the populations of water rails and other ground-nesting birds in the Hebrides, where the mainly fish-eating otter was the only native carnivore. The mink derived from fur farming on Lewis, from whence they spread through Harris, North Uist and South Uist. Mink and ferret eradication programmes have enabled the rail to return to islands including Lewis and Harris, and further projects are ongoing or planned on the Scottish mainland. Locally, habitat may be affected by the drainage of marshes, canalisation of water courses, urban encroachment, and by pollution.
Water rails have been eaten by humans for thousands of years; they were eaten by the Romans, and depicted in wall paintings at Pompeii, and consumption continued through the Middle Ages to modern times.
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