Water rail
Template:Short description Template:Speciesbox
The water rail, western water rail or European water rail (Rallus aquaticus) is a bird of the rail family which breeds in well-vegetated wetlands across Europe, Asia and North Africa. Northern and eastern populations are migratory, but this species is a permanent resident in the warmer parts of its breeding range. The adult is Template:Convert long, and, like other rails, has a body that is flattened laterally, allowing it easier passage through the reed beds 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 incubated 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 omnivorous, 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.
TaxonomyEdit
The rails are a bird family comprising around 150 species. Although the origins of the group are lost in antiquity, the largest number of species and the most primitive forms are found in the Old World, suggesting that this family originated there. However, the genus Rallus, the group of long-billed reed bed specialists to which the water rail belongs, arose in the New World. Its Old World members, the water, African and Madagascar rails, form a superspecies, and are thought to have evolved from a single invasion from across the Atlantic.<ref name=taylor29/> Genetic evidence suggests that the water rail is the most closely related of its genus to the Pacific Gallirallus rails,<ref name=Christidis/> and is basal to that group.<ref name=Trewick/> The water rail was first described by Carl Linnaeus in his 1758 10th edition of Systema Naturae under its current scientific name, Rallus aquaticus.<ref name=Linnaeus1758/> The binomial name is the Latin equivalent of the English "water rail"<ref name=BTO/> that had been used by English ornithologists Francis Willughby in 1676<ref>Template:Cite book</ref> and by Eleazar Albin in 1731.<ref>Template:Cite book</ref>
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.<ref name =blandford>Template:Cite book</ref> It was restored as a full species R. indicus, by Pamela Rasmussen in her Birds of South Asia (2005).<ref name= ras>Template:Cite book</ref><ref>Template:Cite journal</ref> Her treatment has gained acceptance, and is followed in Birds of Malaysia and Singapore (2010).<ref name= malaysia>Template:Cite book</ref> 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.<ref name= tavares/>
FossilsEdit
The oldest known fossils of an ancestral water rail are bones from Carpathia dated to the Pliocene (1.8-5.3 million years ago). By the late Pleistocene, two million years ago, the fossil evidence suggests that the water rail was present across most of its present range.<ref name=tavares/> This species is well-recorded, with over 30 records from Bulgaria alone, and many others from across southern Europe.<ref name=boev2005/><ref name=marco/> and China.<ref name=lucas/> A rail from Eivissa, Rallus eivissensis, was smaller but more robust than the water rail, and probably had poorer flight abilities. In the Quaternary, the island lacked terrestrial mammals, and this distinctive form presumably descended from its continental relative. It became extinct at about the same time as human arrival on the island,<ref name=Mcminn/> between 16,700 and 5,300 BC.<ref name=Alcover/> The nominate race of water rail is now a very rare resident on Eivissa.<ref name=Kellner/>
DescriptionEdit
The adult of the nominate subspecies is a medium-sized rail, Template:Convert long with a Template:Convert wingspan. Males typically weigh Template:Convert and females are slightly lighter at Template:Convert.<ref name=CRC/> The upper parts from the forehead to tail are olive-brown with black streaks, especially on the shoulders. The sides of the head and the underparts down to the upper belly are dark slate-blue, except for a blackish area between bill and eye, and brownish sides to the upper breast. The flanks are barred black and white, and the undertail is white with some darker streaks. The long bill and the iris are red, and the legs are flesh-brown. The sexes are similar; although the female averages slightly smaller than the male, with a more slender bill,<ref name=taylor293/> determining sex through measurements alone is unreliable.<ref name=fuertes/> The juvenile has a blackish crown and a white chin and throat. The underparts are buff or white with darker bars, and the flank markings are brown and buff, rather than black and white. The undertail is buff, and the eye, bill and leg colours are duller than the adult. The downy chick is all black apart from a mainly white bill.<ref name=taylor293/> After breeding, the rail has an extensive moult, and is flightless for about three weeks.<ref name="iucn status 12 November 2021" /> Individual adults can be identified by the markings on the undertail, which are unique to each bird. Adult males have the strongest black undertail streaks.<ref name=ripley/> It has been suggested that the dark barring on the undertail of this species is a compromise between the signalling function of a pure white undertail, as found in open water or gregarious species like the common moorhen, and the need to avoid being too conspicuous.<ref name=Stang/>
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.<ref name=brown/> 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.<ref name=taylor293/>
VocalisationsEdit
The water rail is a vocal species which gives its main call, known as "sharming", throughout the year. This is a series of grunts followed by a high-pitched piglet-like squeal and ending in more grunts. It is used as a territorial call, alarm and announcement. Members of a pair may call alternately, the male giving lower and slower notes than his partner. The courtship song, given by both sexes, is a Template:Not a typo often ending with a trill from the female; the male may sing for hours. The flight call is a sharp whistle, and other vocalizations include a loud repeated creak given by the male when showing the nest site to the female, and a purring given by both parents when at the nest with chicks. The rails are most vocal when setting up a territory and early in the breeding season, when calling may continue at night. Chicks initially cheep weakly, but soon develop a Template:Not a typo begging call.<ref name=taylor293/>
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.<ref name=herremans/>
SubspeciesEdit
There are three recognised subspecies.<ref name=taylor293/>
- R. a. aquaticus Linnaeus, 1758. This is the nominate subspecies that breeds in Europe, North Africa, Turkey, western Asia to the Caspian Sea and western Kazakhstan, and in a narrow band east to central Siberia.<ref name=taylor293/>
- R. a. hibernans Salomonsen, 1931. The Icelandic race, which has slightly warmer brown upperparts than the nominate form. The bars of the flanks are dark brown, not black, and the bill is somewhat shorter; the grey of the underparts may have a brown tinge.<ref name=taylor293/>
- R. a. korejewi Zarudny, 1905. (includes the dubious forms deserticolor, tsaidamensis and arjanicus). This subspecies breeds in south central Asia from southern and eastern Iran east to Eastern China (Sometimes in Beijing, Shanghai etc.), and in the Indian subcontinent in Kashmir and Ladakh. It is slightly larger than the nominate race, with paler brown upperparts and slightly paler slate underparts. It has a weak brown stripe through the eye.<ref name=taylor293/><ref name=ali/>
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.<ref name= tavares/>
Distribution and habitatEdit
The water rail breeds across temperate Eurasia from Iceland and Ireland discontinuously to North Africa, Saudi Arabia and western China. Its distribution in Asia is poorly studied.<ref name=taylor293/>
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.<ref name=tavares/>
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 Western Isles, suggesting that the Icelandic form was a partial migrant.<ref name=BWP/> 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.<ref name=BWP/> A specimen of the nominate population labelled as "Baluchistan" and collected by Richard Meinertzhagen is considered of doubtful provenance.<ref name=Rasmussen2005/> 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.<ref name=taylor293/>
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, reedmace, irises, bur-reed or sedges.<ref name=taylor293/> 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.<ref name=DeKroon/> Where it occurs, saw-sedge provides good breeding habitat, its tall (Template:Convert) dense structure providing good cover for the nesting rails.<ref name=Mommers/> The preferred habitat is Phragmites reedbed with the plants standing in water,<ref name=jenkins/> with a depth of Template:Convert, 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,<ref name=taylor293/> and it occurs in Kashmir in flooded sugarcane fields.<ref name=ali/> 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.<ref name=virkkala/> 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.<ref name=61N/>
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 tits (reed "wigwams" 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.<ref name=Cocker/> Although mainly a lowland species, the water rail breeds at Template:Convert in the Alps and Template:Convert in Armenia.<ref name=taylor293/> An Italian study suggested that reed bed birds need a minimum area of wetland for breeding, which for the water rail is about Template:Convert,<ref name=ijz/> although the highest densities are in marshes of Template:Convert or more.<ref name=virkkala/>
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,<ref name=taylor293/> or even out onto exposed ice.<ref name=Mullarney/> 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.<ref name=Jenkins1995/> 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.<ref name=taylor293/> This species sometimes wanders well outside its normal range and vagrants have been found in the Azores, Madeira, Mauritania, the Arctic,<ref name=BWP/> Greenland, Malaysia and Vietnam.<ref name="iucn status 12 November 2021" />
BehaviourEdit
This rail is a skulking species, its streaked plumage making it difficult to see in its wetland habitat. Its laterally compressed body allows it to slip though the densest vegetation, and it will "freeze" if surprised in the open.<ref name=Coward/> It walks with a high-stepping gait, although it adopts a crouch when it runs for cover. It swims, when necessary, with the jerky motion typical of rails,<ref name=BWP/> and it flies short distances low over the reeds with its long legs dangling. Although their flight looks weak, water rails are capable of long sustained flights during their nocturnal migrations,<ref name=ali/> and are sometimes killed in collisions with lighthouses or wires.<ref name=Coward/> British-ringed birds have been recovered from as far away as Poland, Czechoslovakia and Sweden.<ref name=glue/>
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.<ref name=taylor293/>
BreedingEdit
The water rail is monogamous and highly territorial when breeding. The birds pair off after arriving at their nesting areas, or possibly even before spring migration. In large wetlands with good conditions birds may nest Template:Convert apart. Territories vary in size, but Template:Convert is typical. The pair give courting and contact calls throughout the breeding season. The male selects the nest site which he shows to the female while posturing with raised back feathers, wings arched over his back, tail spread and bill pointed vertically downwards. This display is accompanied by a loud call. Before mating, he raises his wings and tail, and bows with his bill touching his breast. The male feeds the female during courtship, and, when incubating, she may leave the nest to display to the male, walking round him, calling softly, rubbing her bill against his and taking short runs to and from him.<ref name=taylor293/>
The nest is made from whatever wetland vegetation is available and built mostly by the male, usually in a single day. It is raised Template:Convert 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 Template:Convert across and about Template:Convert high. It is well hidden and approached by narrow tracks.<ref name=taylor293/><ref name=Coward/><ref name=seebohm/>
The typical clutch is 6–11 eggs across most of the range,<ref name=taylor293/><ref name=BWP/> but appears to be smaller (5–8) in Kashmir at around Template:Convert altitude.<ref name=ali/> Laying dates vary with location, from late March in Western Europe and North Africa, to late May in Kashmir and June in Iceland.<ref name=taylor293/> The clutch size may be smaller early or late in the breeding season.<ref name=Jenkins1999/> 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<ref name=BWP/> that sometimes merging into a single patch.<ref name=seebohm/> 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, Template:Convert, is therefore typical for the species as a whole. The eggs weigh about Template:Convert,<ref name=taylor293/> of which 7% is shell.<ref name=BTO/>
Both parents incubate the eggs, although the female takes the larger share of this duty.<ref name=ali/> The eggs are incubated for 19–22 days to hatching,<ref name=BTO/> with at least 87% success.<ref name=glue/> 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.<ref name=taylor293/> They are independent of their parents after 20–30 days<ref name=BTO/> and can fly when aged 7–9 weeks.<ref name=taylor293/> 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,<ref name=Coward/> but small chicks may be tucked under the wing.<ref name=Cocker/> Sitting birds may stay on the eggs even when approached closely, attack the intruder, or feign injury as a distraction.<ref name=taylor293/> 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.<ref name=glue/> The maximum recorded age is 8 years 10 months.<ref name=BTO/>
FeedingEdit
Water rails are omnivorous, although they mainly feed on animals. These include leeches, worms, gastropods, small crustaceans, spiders, and a wide range of both terrestrial and aquatic insects and their larvae. Small vertebrates such as amphibians, fish, birds and mammals may be killed or eaten as carrion. Vertebrates are impaled with a strike of the bill which breaks the prey's spinal cord. Plant food, which is consumed more in autumn and winter, includes the buds, flowers, shoots and seeds of water plants, berries and fruit.<ref name=taylor293/> In south Asia, paddy (harvested rice kernels) may sometimes be eaten.<ref name=ali/> The young rails are fed mainly on insects and spiders. Food obtained on land or from mud is normally washed in water before it is eaten.<ref name=taylor293/> After rain, rails may probe soft ground for earthworms.<ref name=ripley/> This species will occasionally feed in the open even when not forced to do so by cold weather; Edmund Meade-Waldo described seven rails feeding in an open meadow.<ref name=m-w/> Despite its skulking nature, the water rail appears to thrive in captivity when fed on animal food such as raw meat or earthworms;<ref name=yarrell/> one individual was taught to jump for worms suspended from a fishing rod.<ref name=Cocker/>
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.<ref name=taylor293/> 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 ringers' mist nets. One bird killed a twite caught with it in a Heligoland trap.<ref name=Cocker/> They are also nest predators, particularly of small birds that nest in reeds such as the great reed warbler.<ref name=Hansson2000/> Water rails may defend a winter feeding territory, although this is smaller than when breeding, with individuals perhaps less than Template:Convert apart;<ref name=taylor293/> favoured sites may hold hundreds of birds.<ref name=lack/> Aggressive behaviour outside the breeding season may extend to attacks on other marsh rails such as spotted and Baillon's crake.<ref name=Ciach/>
Predators and parasitesEdit
_lores.jpg){kind=link}
Predators of the water rail include a number of mammals and large birds. The American mink was partly responsible for the extinction of the Icelandic population,<ref name=tavares/> and cats and dogs have also been recorded as killing this species.<ref name=glue/> At least locally, otters will also eat rails and other water birds.<ref name=delaHey2008/> The Eurasian bittern, another reed bed bird, will consume rails,<ref name=zls/> as will grey herons.<ref name=Coward85/> Water rails are particularly vulnerable to the heron when forced out of the cover of the reeds by very high tides.<ref name=Cocker/> Wetland-hunting harriers are predictable predators,<ref name=clarke/> but more unusually, the rail has also been recorded as a prey item of the tawny owl,<ref name=Yalden/> short-eared owl,<ref name=Glue1977/> Eurasian eagle-owl,<ref name=Bayle/> greater spotted eagle,<ref name=Alivizatos/> common kestrel,<ref name=cave/> and night-hunting peregrine falcons.<ref name=dwt/>
Parasites include the sucking lice Nirmus cuspidiculus and Pediculus ralli,<ref name=denny/><ref name=clay/> the tick Ixodes frontalis,<ref name=tick/> and the louse fly Ornithomyia avicularia.<ref name=hill/> The water rail can be infected by the avian influenza virus<ref name=aiv/><ref name=Fereidouni/> and the bacterium Borrelia burgdorferi, carried by Ixodes ticks, which is also a human pathogen causing Lyme disease.<ref name=Schwarzova/> Three lice, 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.<ref name=Palma/> The parasitic flatworm Ophthalmophagus nasciola was found in one rail's nasal sinus,<ref name=Dronen2007/> and at least three species of feather mite have been detected on the plumage.<ref name=Atye/> The louse Philopterus ralli and the nematode Strongyloides avium have been found on the closely related brown-cheeked rail R. a. indicus.<ref name=Sakamoto1968/><ref name=Uchida/>
StatusEdit
.jpg){kind=link}
The water rail's numbers are declining, but it has a large population of 100,000–1,000,000 adults and a huge breeding range estimated at Template:Convert; it is therefore classed as least concern on the IUCN Red List.<ref name="iucn status 12 November 2021" /> In most European countries, the population is either stable or decreasing slightly due to loss of habitat. The rail's range and numbers are increasing in Morocco, with breeding as far south as Oued Massa.<ref name=BWP/> Little is known about the Asian range, but korejewi is a common breeder in Pakistan and Kashmir.<ref name=Rasmussen2005/>
Introduced predators are a threat to vulnerable island populations. In addition to the extirpation 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 farms on Lewis,<ref name=nz/> from whence they spread through Harris, North Uist and South Uist.<ref name=ohbp/> Mink and ferret eradication programmes have enabled the rail to return to islands including Lewis and Harris,<ref name=snh/> and further projects are ongoing or planned on the Scottish mainland.<ref name=bbc/> Locally, habitat may be affected by the drainage of marshes, canalisation of water courses, urban encroachment,<ref name=newatlas/> and by pollution.<ref name=Carpene/>
Water rails have been eaten by humans for thousands of years;<ref name=boev/> they were eaten by the Romans,<ref name=jones/><ref name=Grimm/> and depicted in wall paintings at Pompeii,<ref name=Watson/> and consumption continued through the Middle Ages to modern times.<ref name=Woolgar/>
ReferencesEdit
Cited textsEdit
External linksEdit
Template:Sister project Template:Sister project
- Ageing and sexing by Javier Blasco-Zumeta & Gerd-Michael Heinze (PDF, 5.2 MB)
- Template:BirdLife
- Template:Avibase
- Template:InternetBirdCollection
- Template:VIREO
- Template:IUCN Map
- Template:Xeno-canto species
Template:Portalbar Template:Taxonbar Template:Featured article