Rallidae

(vertebrate zoology) A large family of birds in the order Gruiformes comprising rails, gallinules, and coots.

(Rallidae)

Class: Aves

Order: Gruiformes

Suborder: Grues

Family: Rallidae

Thumbnail description
Small to medium-sized birds with short and deep to long and slender bill, moderately long neck, broad wings, short, soft tail, and strong legs

Size
4.7–24.8 in (12–63 cm); 0.7 oz–9.13 lb (20.41 g–4.14 kg)

Number of genera, species
33 genera; 134 species

Habitat
Wetlands, grasslands, forest, and dense scrub

Conservation status
Extinct in the Wild: 1 species; Critically Endangered: 4 species; Endangered: 12 species; Vulnerable: 16 species; Near Threatened: 9 species; Data Deficient: 4 species

Distribution
Worldwide, except for polar regions and waterless deserts; widely distributed on oceanic islands

Evolution and systematics

The Rallidae is by far the largest family in the Gruiformes. In some classifications the family has been assigned to its own order Ralliformes, while others have allied with to the Charadriiformes; DNA evidence suggests that it shares a common ancestor with both gruiform and charadriiform birds. Skeletal morphology suggests a close alliance with the Psophiidae (trumpeters) and the Heliornithidae (sungrebes and finfoots), and a phylogenetic study of the Gruiformes using morphological characters, published by Bradley Livezey in 1998, places the families Psophiidae, Aramidae (limpkin), Gruidae (cranes), Heliornithidae and Rallidae together in the suborder Grues. On the basis of DNA evidence that the Rallidae may have had a distinct lineage for a long time, it has also been proposed that the rails should be elevated to their own suborder, the Ralli, alongside the Grues.

Fossil evidence tells us little about the origins of the Rallidae. The earliest rail fossils are from the Lower Eocene, about 50 million years ago, but the family may have existed earlier than this. DNA-DNA hybridization studies suggest that rails may have diverged from the other gruiform groups as long as 86 million years ago, in the Upper Middle Cretaceous. The first adequate diagnostic material on fossil rail genera comes from the Upper Oligocene and Lower Miocene, 20–30 million years ago, and by then the birds had attained a morphology similar to that of modern rails. Most continental fossil rails from Pliocene and Pleistocene deposits have been assigned to modern genera.

The geographic origins of modern rails have been obscured by the antiquity, cosmopolitan distribution, and inadequate taxonomy of the family. However, Storrs Olson has shown that the greatest number of rail species and peculiar genera, and the most primitive species, are found in the Old World tropics. The New World has fewer groups, most of which are apparently derived from Old World stem groups. A few genera appear to have specialized and radiated in the New World, some of which (e.g. Rallus and Fulica) have reinvaded the Old World.

Several classifications have been proposed for the family. The generally accepted classification, published in 1973 by Olson, listed 35 genera in two subfamilies, the Himantornithinae and Rallinae, the former containing one species, Himantornis haematopus, the nkulengu rail of Africa. Livezey's classification also recognizes these subfamilies. Sibley and Ahlquist have suggested that the flufftails (Sarothrura) of Africa and Madagascar diverged from the rest of the group about 60 million years ago and should be separated into a family Sarothruridae within its own superfamily, the Sarothruroidea.

In this work we follow Olson and Livezey's subfamily treatment and Olson's taxonomic treatment regarding genera—modified to some extent by subsequent studies. Within the family, 33 genera containing 134 extant species and 312 subspecies are recognized, following the list published in 1998 in the book Rails: a guide to the rails, crakes, gallinules and coots of the world by Barry Taylor.

Two "natural groups" within the Rallidae are usually recognized: the crakes, rails, and wood-rails, most of which are terrestrial; and the gallinules (including moorhens) and coots, which are more aquatic. The term "rail" is applied to the whole family and also to longer-billed species in many genera, while "crake" is applied mostly to the smaller, short-billed, species, particularly in the genera Laterallus and Porzana. "Gallinule" can cover all the birds in the second group except the coots, though it is often restricted to Gallinula and Porphyrio.

Physical characteristics

The rails are a relatively homogeneous group of birds, ranging in size from the tiny black rail (Laterallus jamaicensis), 4.7 in (12 cm) long and weighing 0.7 oz (20 g), to the flightless takahe (Porphyrio mantelli) 24.8 in (63 cm) long and weighing up to 9.2 lb (4.2 kg). The sexes are usually similar in size but in a few species the male is markedly larger than the female.

Rail plumage is often cryptic, common colors being somber browns, chestnut, black, blue-gray, or gray, but the Porphyrio gallinules are predominantly iridescent purple, blue, or green. The upperparts are often spotted, barred, or streaked and the flanks strongly barred, while the undertailcoverts may contrast strongly with the rest of the plumage. In most species the sexes are very similar in appearance, exceptions including the flufftails and the New Guinea Rallina forest-rails. Only the watercock (Gallicrex cinerea) shows any significant seasonal change in plumage color or pattern. The juvenal plumage is often a duller, less patterned version of the adult plumage.

The downy plumage of most species is black or dark brown, but the nkulengu rail chick is cryptically patterned with brown, black, and white, closely resembling precocial chicks of other orders. Some chicks, especially those of coots (Fulica), have distinctively colored filoplumes or bristles. Coots, gallinules (Porphyrio), and moorhens (Gallinula) have brightly colored bare skin on the head, and such prominent features act as signals for feeding.

The bodies of rails are often laterally compressed, allowing easy movement through dense vegetation, and the neck can be quite long. The wings are short, broad, and rounded. In some species the alula has a sharp claw, used by the young, and possibly also by adults, when climbing. Short flights are usually low and weak, but some species migrate or disperse over long distances. The tail is short and soft.

The bill shape is variable: from long and thin to short and fine, straight or slightly down-curved; or short and laterally compressed; or short and heavy. It is often brightly colored. Gallinules and coots have a frontal shield that may be of a contrasting color to the bill. Shield and bill colors often become duller in the nonbreeding season, when the shield may also shrink.

Rails have strong, often long, legs. The toes are often long, for walking on marsh vegetation. In some species the legs and feet are brightly colored. Coots have the pelvis and legs modified for diving, and lateral lobes on the toes aid swimming.

Flightlessness is a well-known feature of the family and all flightless rails occur on islands. Of the 134 extant rail species, 41 are known only from islands, including New Guinea, New Zealand, and Madagascar, and 24 (59%) of these are flightless. Flightlessness has evolved many times within the family, often and repeatedly on predator-free islands. The energetic cost of flight is high and flight muscles and associated structures average 20–25% of body weight in typical birds. Where such costs do not convey the benefits of dispersal and escape from predators it is obviously advantageous to become flightless. The muscles and bones of the wing and pectoral girdle are greatly reduced, the feathers become loosely constructed and the leg muscles usually become better developed.

The strong tendency of rails to become flightless suggests a predisposition to the condition, and rails are pre-adapted to coping with some of its restrictions. Thus many volant species are behaviorally flightless, avoiding predators by running. Many are temporarily flightless during wing molt, and the postnatal development of flight in most species is slow.

Distribution

Rails occur throughout the world, being absent only from polar regions, waterless deserts, and mountains above the snow line. Of the 33 rail genera, four (Porzana, Porphyrio, Gallinula, and Fulica) occur worldwide. The genus Porzana includes 13 species of small rails, one of which, Baillon's crake (Porzana pusilla), ranges from western Europe through Africa and Asia east to Japan and Australasia.

The genus Porphyrio has five species of medium to very large gallinules, including the purple swamphen (Porphyrio porphyrio), which has a similar range to Baillon's crake. In the genus Gallinula, the common moorhen (Gallinula chloropus) occurs from the Americas east through Africa and Eurasia to the Malay Archipelago; farther east it is replaced by the very similar dusky moorhen (Gallinula tenebrosa). Although moorhens are commonly regarded as wetland birds, two species occur in forest: the Samoan moorhen (Gallinula pacifica) and the San Cristobal moorhen (Gallinula silvestris). The center of the coots' species diversity is in South America, where eight of the 11 species occur.

The relatively unspecialized genus Gallirallus, with 10 extant and five recently extinct species, is distributed largely from Indonesia through Australasia to western Pacific islands. Seven extant species are flightless, as were all the recently extinct species. The islands in this region also support 17 other endemic rails, eight flightless, and seven of these in five endemic genera. The genus Gymnocrex contains three species of very distinctive, long-legged forest rails of Indonesia and New Guinea, one of which, the Talaud rail (Gymnocrex talaudensis) was discovered only in 1996.

Africa and Madagascar have 23 endemic rail species, with 15 species in six endemic genera, including Sarothrura (the flufftails). In comparison, 51 rail species occur only in the Americas, including 27 in eight endemic genera, the most diverse of which is Laterallus, with nine species. South and Central America are home to all seven species of the wood-rails (Aramides). Six of the nine Rallus species occur only in the Americas, including the well-known clapper and king rails (Rallus longirostris and R. elegans).

Most Holarctic rails are migratory, and five of the nine species that breed in the western Palaearctic winter in sub-Saharan Africa. All rails that breed in North America are migratory to some extent. Relatively little is known about the migrations of species that breed from India east to Japan and south through the Oriental region, but evidence suggests that many birds that breed in the northern regions of Asia move south after breeding. Even less is known about the movements of South American rails, but most of the species known or suspected to be migratory or dispersive inhabit wetlands or wet grassland. All rails occurring widely in Australia are migratory, dispersive, nomadic, or irruptive. In Africa, some species move away from the equator to breed during the rains.

The widespread occurrence of rails on oceanic islands reflects these birds' powers of dispersal and their tendency to vagrancy. The high degree of long-distance vagrancy in the family is also indicative of the readiness with which rails are blown off course by unfavorable winds as a result of their relatively poor flight performance. The purple gallinule (Porphyrio martinica) is a vagrant to South Africa, but there are no instances of African rails occurring in the Americas.

Habitat

The cosmopolitan distribution of the family reflects the ability of rails to adapt to a great diversity of habitat types, both natural and artificial, including wetland, grassland, savanna, scrub, and forest.

Although the greatest number of species occurs in wetland habitats, many species occupy forest habitats in tropical regions. The most primitive living rail, the nkulengu rail, is a forest bird, as are the members of other primitive or unspecialized genera such as Aramides, Canirallus, and Gymnocrex. Species in the most specialized or derived genera such as Rallus, Porzana, Gallinula, and Fulica are aquatic or marsh-dwelling. This suggests that forest was the primitive habitat of the family.

Rails occupy all types of vegetated wetlands, plus some open water habitats. Freshwater wetland habitats include swamps, bogs, marshes, floodplains, pans, ponds, ditches, rice fields, and vegetation fringing streams, rivers, canals, and lakes. Some species, such as the white-browed crake (Porzana cinerea) of Asia and Australasia, and Porphyrio species, prefer floating vegetation, on which they search for food. Some rails occur at coastal wetlands such as lagoons, saltmarshes, tidal creeks, and mudflats, while mangroves are an important habitat for species such as some South American Aramides wood-rails. Coots, the most aquatic rails, occupy fresh to saline waterbodies.

Forest habitats range from low to high altitudes and include primary and secondary growth, riverine and swamp forest, overgrown and abandoned cultivation at forest margins, banana groves, cassava plantations, and dense evergreen or deciduous thickets. Substrates may be clear, with leaf-litter, soft earth or mud, or may have dense herbaceous vegetation. Some species, such as the gray-throated rail (Canirallus oculeus) of Africa and Woodford's rail (Nesoclopeus woodfordi) of the southwest Pacific, occur at forest streams, swamps, or muddy patches, but others are not associated with wet areas.

A few species occur in dense grassland habitats, which may be wet to predominantly dry, the latter including savanna, pampas, meadows, and crop fields. Grassland habitats may be permanently or seasonally occupied; for example, the African crake (Crex egregia) occurs in seasonally moist to wet grassland, which is frequently burned during the dry season, forcing the birds to emigrate after breeding.

Most rails do not have specialized diets and this enables many to exploit ephemeral or atypical habitats. They are able to colonize islands where, in the absence of competitors and predators, they can radiate to occupy almost any available terrestrial niche. They are capable of adapting to harsh conditions on remote oceanic islands. The recently extinct Ascension rail (Atlantisia elpenor) lived on Ascension Island, where the terrestrial environment consists of bare, waterless tracts of lava and ash. It apparently obtained its food and water from the eggs and regurgitated prey of the seabirds, which formerly nested on Ascension in great numbers. The spotless crake (Porzana tabuensis) of the Pacific region, has successfully colonized islands. It normally occurs in a great variety of wetland and scrub habitats, but on some islands it occupies dry rocky habitats with no water.

For rails that feed chiefly on invertebrates, the structure of the vegetation and the nature of the substrate are the most important factors influencing habitat choice. The Virginia rail (Rallus limicola) avoids marshes with high stem densities or large amounts of residual vegetation—features that impede movement—whereas vegetation height is not important if adequate overhead cover is present. It needs shallow water and a substrate with a high invertebrate abundance, and is most common in wetlands with 40–70% upright emergent vegetation interspersed with open water, mudflats, or matted vegetation. The buff-spotted flufftail (Sarothrura elegans) occupies natural forests and thickets, but also areas dominated by alien vegetation. Its invertebrate food is equally abundant on substrates below exotic vegetation and those below indigenous plants.

Behavior

Most rails are solitary or occur in pairs, family parties, or small groups. The most gregarious species are the coots, most of which associate in large monospecific flocks outside the breeding season. Some gallinules and moorhens also associate in loose flocks when not breeding. The black-tailed native-hen (Gallinula ventralis) of Australia may occur in flocks of up to 20,000 birds during its periodic irruptions.

Wetlands and lush grasslands are structurally simple and may be highly productive, with food concentrated in a narrow spatial range. In such conditions it may be possible for males to control territories in which two or more females can breed, relegating less successful males to suboptimal territories, or to none at all. This strategy may apply to the yellow rail and the corncrake, while polyandry in the striped crake may have evolved in response to great variability in breeding conditions and the availability of abundant food in the breeding habitat.

In the promiscuous Porphyrio and Gallinula species, social structure and mating systems are complex. The common moorhen is normally monogamous, but immatures from earlier broods, and sometimes other mature birds, often help care for chicks. Polyandrous trios and cooperative nesting also occur, while intraspecific brood parasitism is regular. Monogamy prevails in most races of the purple swamphen, but in two races birds often live in communal groups. In New Zealand, stable groups, usually of kin, hold permanent territories and are polygamous, usually with two to seven breeding males, one to two breeding females, and one to seven nonbreeding helpers (offspring from previous matings). Unstable groups are usually non-kin and are promiscuous, with much aggression and many male members, and are largely unsuccessful. Within a stable group mate-sharing is total and multiple paternity prevails. Dominant females lay in a common nest and all group members care for the young. Habitat saturation and a shortage of prime breeding territories appear to be responsible for this breeding strategy.

Agonistic behavior in rails is common and often conspicuous. In the purple swamphen, the position of the tail and wings is important in agonistic display, while differing body postures indicate aggression or anxiety. Moorhens and coots share similar agonistic displays, in which the degree of prominence of the frontal shield is often an important component.

Rails are territorial, many species defending territories only while breeding. Winter feeding territories are maintained by the water rail (Rallus aquaticus), the spotted crake (Porzana porzana), and the African crake, and this phenomenon is probably more widespread than is known.

Most rails are very vocal, with an extensive repertoire, as is to be expected in birds that inhabit dense cover where visual contact is often very limited and communication by sound is important. Calls include screams, squeals, trills, whistles, whines, hoots, moans, booms, rattles, clicking and ticking notes, snoring noises, humming and buzzing sounds, trumpets, roars, grunts, barks, frog-like croaks, and snake-like hisses; calls of some small species may be very insect-like. The advertising and territorial calls of many species are given in a repetitive series, are often loud, and are given most commonly in the early morning, the evening, and at night.

Most rails normally keep within dense cover and are adept at moving around without causing any noise or disturbance of the vegetation. When alarmed, most run rather than fly, and they can melt quietly and rapidly into cover, compressing the body laterally for easy passage through vegetation. Rails often walk with bobbing head and flicking tail. Tail jerking is used in visual orientation and signaling between con-specific individuals, but in the common moorhen and the purple swamphen it is also directed toward potential predators as an alertness signal and pursuit deterrent.

Many rails are predominantly crepuscular. Some terrestrial and marsh species forage at night as well as by day and it is possible that nocturnal activity is largely confined to species of open habitats where visibility at night is relatively good. Rails that forage in tidal areas are often active during low tides at night. Most rails normally roost singly, in pairs, or in family groups, generally on the ground in dense cover, but sometimes above ground in dense vegetation such as bushes and trees.

Feeding ecology and diet

Rails are characteristically omnivorous, generalized feeders, often opportunistic and able to take advantage of new food sources. In general the most aquatic species, such as the gallinules and coots, are largely herbivorous, while those that inhabit terrestrial and marshy habitats are either omnivorous or take predominantly animal food, at least in the breeding season.

Many rails appear to feed largely on the most abundant foods available at any time. A few species take only a restricted range of prey or plant material, and such specialization is usually a reflection of the limited variety of suitable food available. Thus rails that forage in mangroves feed largely on crabs, examples being the chestnut rail (Eulabeornis castaneoventris) and the rufous-necked wood-rail (Aramides axillaris).

Invertebrates are the principal diet of many species, and commonly include worms, mollusks, crustaceans, spiders, and insects. Some rails take vertebrate prey, including small fish, amphibians and their tadpoles, small reptiles (lizards, snakes, and turtle eggs and hatchlings), and the eggs and young of other birds, while a few will eat carrion. Forest-dwelling rails probably eat fewer plant foods than those in other habitats.

Many types of plant foods are eaten by rails, including seeds, fruits, shoots, stems and leaves, tubers, bulbs, rhizomes and roots, as well as marine and filamentous algae, fungi, lichens, and ferns. Cultivated plants such as vegetables, cereal and fodder crops, fruit, and taro are taken by some species. Coots are almost entirely herbivorous, but some aquatic insects, mollusks, and crustaceans are taken, and coots will sometimes eat eggs, fish, carrion, duck-food pellets, and even food scraps from campsites.

Although most rails drink fresh water, some species are able to survive on oceanic islands with no fresh water. These rails may drink salt water or may obtain most of their water from their food. Thus the white-throated rail (Dryolimnas cuvieri) drinks salt water on Aldabra, and the buff-banded rail (Gallirallus philippensis) can exist on islands with no fresh water. Some rails, such as the saltmarsh-dwelling clapper rail, possess well-developed supra-orbital (nasal) glands, which function in the excretion of salt.

Bill size and shape provide a good indication of a rail's foraging habits. Species with long thin bills probe for invertebrate food in shallow water, soft ground, and litter, while those with small, fine bills take small invertebrates and seeds from the substrate, shallow water, and low vegetation. Those with straight bills of moderate length and depth take a wide variety of small to large food items, chiefly by probing, gleaning, digging, sifting leaf-litter, stabbing at large prey, and raking in earth and mud. Thick-billed species tear and slice vegetation, and dig or pull up the underground parts of plants.

Some gallinules use the foot to grasp and manipulate food. The purple swamphen uses its bill to pull out emergent plants and then grasps them in the foot while eating the bases.

Only coots regularly dive for food, but coots and Gallinula species regularly up-end when feeding. The white-browed crake often feeds while swimming, floating with the neck extended parallel with the surface and reaching out to capture insects.

Some species show seasonal variations in the proportions of animal and plant food taken, and this may reflect seasonal changes in the availability of food, the use of different habitats when birds are on migration or in wintering areas, or the need for a greater consumption of protein in the breeding season to satisfy the requirements for egg-laying. Many species increase their intake of animal food in the spring and summer, and of plant food in the autumn and winter. Most rail chicks, even those of herbivorous species, are fed primarily on animal food.

Reproductive biology

With the exception of some coots, moorhens, and gallinules, little is known about the breeding of most rails. The nest, eggs, and young of 23 species remained undescribed in 2001.

Monogamy is the predominant mating system in the family. This is to be expected because, although rail chicks are precocial or semi-precocial, they need intensive care at an early age, when they are fed, guarded and brooded by their parents. A non-monogamous mating system occurs in the wild in only five rails: the corncrake (Crex crex), the purple swamphen, the common moorhen, the dusky moorhen and the Tasmanian native hen (Gallinula mortierii), and in captivity in the yellow rail (Coturnicops noveboracensis) and the striped crake (Aenigmatolimnas marginalis).

Most species appear to breed seasonally, during the spring and summer in temperate regions and during the wet seasons in the tropics. Most exceptions to this pattern involve tropical or subtropical species that may have extended or ill-defined breeding periods.

Some species may breed throughout the year if conditions remain suitable, examples from Africa being the common moorhen and the red-knobbed coot (Fulica cristata). Studies of some rails in southwest Australia have shown that in most species the laying period is correlated with peak rainfall, day length, and temperature. The timing of vegetation development is often important to the initiation of nesting in rails of marshy habitats. Thus in the state of Ohio, peak nest initiation of the common moorhen occurs when vegetation height is 18–40 in (45–100 cm) and its growth rate is greatest. The breeding season of the Tasmanian native-hen is determined by rainfall, as it depends on fresh young plant growth.

Courtship feeding and allopreening are common, and aggressive-looking courtship chases often lead to copulation. In some species the male's courtship display involves bowing, and may involve the display of bold flank patterns or contrastingly colored undertail-coverts. Gallinules, moorhens, and coots show the most complex courtship and mating behavior. In the purple swamphen, courtship usually starts with allopreening but the male may also present aquatic plant material in his bill to the female, and the female solicits copulation by adopting the arch-bow posture. Coots and moorhens share similar components in their sexual displays, including a bowing-and-nibbling ceremony (in which one bird is submissive while the other preens it), a greeting and passing ceremony, and a courtship chase.

Nests are usually concealed in thick ground vegetation, often near or over water, but some species nest in dry areas and some in trees. Nest materials are often gleaned from the vegetation closest to the nest site, and nests are often built by both sexes. The nest is usually cup-shaped, but is domed in some species, including most Laterallus crakes. Nests in grass and emergent vegetation often have surrounding vegetation woven into a concealing canopy over the bowl, while nests in wetlands often have ramps up to the bowl. Some species build nests that float or are attached to aquatic vegetation. The giant coot (Fulica gigantea) and horned coot (Fulica cornuta) build enormous permanent nests of aquatic vegetation which, in the horned coot, is usually placed on a conical mound of stones, up to 13 ft (4 m) in diameter at its base, about 2 ft (60 cm) high and about 3 ft (1 m) in diameter at the top. The structure may weigh about 1.5 tons; each stone weighs up to 1 lb (450 g) and both adults collect stones and carry them to the nest in the bill.

Rail eggs are usually approximately oval, smooth, and fairly glossy. The ground color is white to dark tan, usually blotched or spotted with red-brown, gray, mauve, or black. Clutch size varies from one to 19 (most frequently five to 10), and dumping or laying by more than one female in the same nest may occur. Incubation is by both sexes in most species, and incubation periods are 13–31 (usually 15–19) days per egg. Hatching may be synchronous or asynchronous.

Rail chicks hatch covered in down and are precocial or semi-precocial, usually leaving the nest after one to three days. Chicks are usually fed bill-to-bill at first and are normally tended by both parents, in some species also by helpers. The fledging period is four to eight weeks but in the giant coot it is about four months. Chicks' legs and feet grow rapidly, reaching full size before the rest of the body, but the growth of the wings is generally much retarded. The young usually become independent as soon as they are fully fledged. First breeding usually occurs when the birds reach their first year.

One or two broods are usually reared, and many species will re-lay several times after failure. Nesting success varies widely in the few species for which figures are available, often depending on factors such as food supply, predation, and flooding. In general, early nests are often more successful than later ones. In North American species, nesting success is given as: 10–100% for the clapper rail, 81% for the king rail, 53% for the Virginia rail, 49–91% for the purple gallinule and over 80% for the American coot (Fulica americana). In many species hatching success is often high, whereas chick survival may be much lower.

Conservation status

The IUCN Red List of birds, published in 2000, shows that, of the 134 living rail species, 33 (almost 25%) are Threatened, including four that are Critically Endangered, 12 Endangered, 16 Vulnerable and one, the Guam rail (Gallirallus owstoni) Extinct in the Wild. A further nine species are listed as Near Threatened and four as Data Deficient. Thus the survival of 62 species (46%) of rails gives cause for concern.

Of 20 rail taxa (16 species and four subspecies) that have become extinct since 1600, 17 (85%) were flightless. The extinction of these rails provides a classic example of the particular vulnerability of island endemics. The principal causes of extinctions among island rails have been introduced mammalian predators such as cats, dogs, rats, mongooses, and pigs, indiscriminate hunting by the first people to visit the islands, and habitat destruction by introduced goats, rabbits, and fire. Introduced predators have probably been responsible for more extinctions than any other cause. Several extant island species are still at risk from the possible accidental introduction of mammalian predators to their islands.

Habitat destruction does not seem to be a critical problem for any threatened island rail at present, but is certainly a major threat to many continental species. For example, the plain-flanked rail (Rallus wetmorei) has a very restricted distribution in coastal Venezuela, where its mangrove and lagoon habitats are being destroyed by housing development, oil exploration, and diking.

Many rails are probably undergoing a continual population decline, largely through habitat loss. The wholesale and enormous destruction of indigenous forests is a severe threat to some species, especially in southeast Asia and South America. Palustrine wetlands are under threat worldwide and are disappearing at an alarming rate. Small crake species, such as the black rail, which inhabit the edges of marshes, are generally more threatened by habitat destruction than are other rails, which live in the interiors of marshes or alongside open water.

Great efforts have been made to save some threatened species, involving captive breeding and reintroduction of birds into the wild, habitat management, and predator control. The takahe and the Guam rail are two good examples.

Significance to humans

Rails have had little association with humans and have no significant place in art, literature, or legend. This is presumably because most rails are unobtrusive, cryptic, and hard to see; many people are not even aware that they exist.

However, one rail did excite the interest of ancient civilizations. The purple swamphen is depicted climbing on papyrus stems in the Egyptian wall paintings at Medum. The Greeks and Romans refrained from eating the "Porphyriõn" but imported the birds and placed them in palaces and temples, where they walked around freely as worthy guests by virtue of the nobleness of their bearing, the graciousness of their nature, and the beauty of their plumage.

Local superstitions about rails include those held by some African peoples to explain the strange calls heard from forest or marsh. The song of the buff-spotted flufftail, one of the most evocative sounds of the African rainforest, is sometimes believed to be the wail of a banshee, or the sound of a chameleon mourning for its mother, whom it killed in an argument over some mushrooms. The extinct Kosrae crake (Porzana monasa) of the Caroline Islands remains a legend among the islanders, since it was regarded as a sacred bird before the arrival of Christian missionaries.

In the Cocos-Keeling Islands, the buff-banded rail (Gallirallus philippensis) is apparently used to hatch chicken eggs in place of domestic hens. In Bangladesh the watercock (Gallicrex cinerea) is used as a fighting bird, as in cockfighting. In South America the giant wood-rail (Aramides ypecaha) is often kept in captivity and individuals are sold in village shops.

Rails have long been hunted for food and sport in many parts of the world and the Eurasian coot (Fulica atra) is still shot in Mediterranean countries for these purposes. In Europe the corncrake (Crex crex) was commonly hunted for food in the past, and is still caught in Egypt during the ancient practice of quail netting. In the United States the larger rails may still be hunted legally and in Audubon's time soras (Porzana carolina) and clapper rails (Rallus longirostris) were heavily hunted. People in Africa, Asia, and South America often trap forest rails, while marsh rails are widely hunted in Asia. Rail eggs are regarded as highly palatable, and common moorhens were formerly extensively exploited for their eggs in Asia. The giant coot is also exploited for its eggs.

The larger rails may occasionally damage crops or pasture. The Tasmanian native-hen has been falsely accused of this, and was at one stage declared vermin. The purple swamphen is said to do considerable damage to growing rice crops in India and Bangladesh, but such damage must be highly localized. The purple gallinule is regarded as a pest in rice fields in some Neotropical areas.

Species accounts

Resources

Bird, D.M. The Bird Almanac: The Ultimate Guide to Essential Facts and Figures of the World's Birds. Buffalo: Firefly Books, 1999.

Craig, J.L., and I.G. Jamieson. "Pukeko: different approaches and some different answers." In Co-operative Breeding in Birds: Long-term Studies of Ecology and Behavior, edited by P.B. Stacey and W.D. Koenig. Cambridge: Cambridge University Press, 1990.

Cramp, S., and K.E.L. Simmons, eds. Hawks to Bustards. Vol. 2, The Birds of the Western Palearctic. Oxford: Oxford University Press, 1980.

Fjeldså, J., and N. Krabbe. Birds of the High Andes. (Copenhagen and) Svendborg: Zoological Museum, University of Copenhagen and Apollo Books, 1990.

Glutz von Blotzheim, U.N., K.M. Bauer, and E. Bezzel. Handbuch der Vögel Mitteleuropas. Vol. 5. Frankfurt am Main: Akad. Verlag, 1973.

Marchant, S., and P.J. Higgins, eds. Raptors to Lapwings. Vol. 2, Handbook of Australian, New Zealand and Antarctic Birds. Melbourne: Oxford University Press, 1993.

Olson, S.L. "A synopsis of the fossil Rallidae." In Rails of the World: A Monograph of the Family Rallidae, by S.D. Ripley. Boston: Godine. 1977.

Potapov, R.I., and V.E. Flint, eds. Galliformes, Gruiformes. Vol. 4, Handbuch der Vögel der Sowetjunion, edited by V.D. Illicev and V.E. Flint. Wittenberg Lutherstadt: A. Ziemsen Verlag, 1987.

Stattersfield, A.J., and D.R. Capper, eds. Threatened Birds of the World: The Official Source for Birds on the IUCN Red List. Cambridge, United Kingdom: BirdLife International, 2000.

Tacha, T.C., and C.E. Braun, eds. Management of Migratory Shore and Upland Game Birds in North America. Washington, DC: International Assoc. Fish and Wildlife Agencies, 1994.

Taylor, B., and B. van Perlo. Rails: A Guide to the Rails, Crakes, Gallinules and Coots of the World. Sussex: Pica Press, 1998.

Urban, E.K., C.H. Fry, and S. Keith, eds. The Birds of Africa. Vol. 2. London: Academic Press, 1986.

Wanless, R.M. The Reintroduction of the Aldabra Rail Dryolimnas cuvieri aldabranus to Picard Island, Aldabra Atoll. MSc thesis: University of Cape Town, 2002.

Eddleman, W.R., F.L. Knopfe, B. Meanley, F.A. Reid, and R. Zembal. "Conservation of North American Rallids." Wilson Bulletin 100 (1988): 458–475.

Halse, S.A., and R.P. Jaensch. "Breeding Seasons of Water-birds in South-western Australia—The Importance of Rainfall." Emu 89 (1989): 232–249.

Livezey, B.C. "A Phylogenetic Analysis of the Gruiformes (Aves) Based on Morphological Characters, with an Emphasis on the Rails (Rallidae)." Philosophical Transactions of The Royal Society of London B 353 (1998): 2077–2151.

McRae, S.B., and T. Burke. "Intraspecific Brood Parasitism in the Moorhen: Parentage and Parasite-host Relationships Determined by DNA Fingerprinting." Behaviorial Ecolology and Sociobiolology 38 (1996): 115–129.

Olson, S.L. "Evolution of the Rails of the South Atlantic Islands (Aves: Rallidae)." Smithsonian Contribtributions to Zoolology 152 (1973): 1–53.

Olson, S.L. "A Classification of the Rallidae." Wilson Bulletin 85 (1973): 381–446.

"Black Rail." Illinois Birds. 30 June 1998. Illinois Natural Resources Information Network. 06 Dec. 2001

Tan, Ria. "White-breasted Waterhen." Apr 2001. Sungei Buloh Nature Park. 06 Dec. 2001

[Article by: Barry Taylor, PhD]

The noun has one meaning:

Meaning #1: rails; crakes; gallinules; coots
  Synonym: family Rallidae

Rails Fossil range: Early Eocene - Recent
American Purple Gallinule, Porphyrio martinica
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Aves Subclass: Neornithes Infraclass: Neognathae Superorder: Neoaves Order: Gruiformes Suborder: Ralli Family: Rallidae Vigors, 1825
Genera
Some 40 living, and see below.

The rails, or Rallidae, are a large cosmopolitan family of small to medium-sized birds. The family exhibits considerable diversity and the family also includes the crakes, coots, and gallinules. Many species are associated with wetlands, although the family is found in every terrestrial habitat except dry deserts, polar regions and alpine areas above the snow line.

Members of the Rallidae are found on every continent except Antarctica. There are numerous island species. The most common habitats are marshland or dense forest. Rails are especially fond of dense vegetation.^[1]

Contents 1 Ecology 2 Morphology 2.1 Flight and flightlessness 3 Behavior and ecology 3.1 Reproduction 4 Rallidae and humans 4.1 Threats and conservation 5 Systematics and evolution 5.1 Extant (living) genera 5.2 Recently extinct genera 5.3 Late Quaternary prehistoric extinctions 5.4 Fossil record 5.5 Doubtfully placed here 6 Footnotes 7 References

Ecology

The most typical family members occupy dense vegetation in damp environments near lakes, swamps, or rivers. Reed beds are a particularly favoured habitat. They are omnivorous, and those that migrate do so at night: most nest in dense vegetation. In general, they are shy and secretive birds, and are difficult to observe.

Most species walk and run vigorously on strong legs, and have long toes which are well adapted to soft, uneven surfaces. They tend to have short, rounded wings and although they are generally weak fliers, they are, nevertheless, capable of covering long distances.

Island species often become flightless, and many of them are now extinct following the introduction of terrestrial predators such as cats, rats and pigs.

Many reedbed species are secretive (apart from loud calls), crepuscular, and have laterally flattened bodies. In the Old World, long-billed species tend to be called rails and short-billed species crakes. North American species are normally called rails irrespective of bill length. The smallest of these is the Swinhoe's Rail, at 13 cm (5 inches) and 25 grams.

The larger species are also sometimes given other names. The black coots are more adapted to open water than their relatives, and some other large species are called gallinules and swamphens. The largest of this group is the Takahē, at 65 cm (26 inches) and 2.7 kg (6 lbs).

The rails have suffered disproportionally from human changes to the environment and it is estimated that several hundred species of island rail have become extinct because of this. Several island species of rail remain endangered and conservation organisations and governments continue to work to prevent their extinction.

Morphology

South Island Takahē (Porphyrio hochstetteri) from behind, showing the short, soft and fluffy remiges typical of flightless rails

The rails are a fairly homogeneous family of small to medium sized ground living birds. They vary in length from 12 cm to 63 cm and in weight from 20 g to 3000 g. Some species have long necks and in many cases they are laterally compressed. The bill is the most variable feature within the family: in some species it is longer than the head (like the Clapper Rail of the Americas), in others it may be short and wide (as in the coots), or massive (as in the purple gallinules).^[2] A few coots and gallinules have a "frontal shield", which is a fleshy rearward extension of the upper bill. The most complex frontal shield is found in the Horned Coot.^[3]

Rails exhibit very little sexual dimorphism in either plumage or size.

Flight and flightlessness

The wings of all rails are short and rounded. The flight of those Rallidae able to fly, while not very powerful, can be sustained for long periods of time and many species undertake annual migrations. The weakness of their flight, however, means that they are easily blown off course and thus are common vagrants, a characteristic that has led them to colonize many isolated oceanic islands. Furthermore, these birds often prefer to run rather than fly, especially when in dense habitat. Some are also flightless at some time during their moult period.^[4]

Many island rails are flightless because small island habitats without threatening predators often eliminate the need to fly or move long distances. Flight makes intense demands, with the keel and flight muscles taking up to a quarter of a bird's weight in Rallidae species. Reducing the flight muscles, along with the corresponding lowering in metabolic demands, reduces the flightless rail's energy expenditures.^[5] For this reason flightlessness makes it easier to survive and colonize an island where resources may be limited.^[6] Flightlessness can evolve extremely rapidly in island rails; it took as little as 125,000 years for the Laysan Rail to lose the power of flight and evolve the reduced, stubby wings only useful to keep balance when running quickly.^[7]

Behavior and ecology

In general, members of Rallidae are omnivorous generalists. Many species will eat invertebrates, as well as fruit or seedlings. A few species are primarily vegetarian.^[1]

The calls of Rallidae species vary and are often quite loud. Some are whistle-like or squeak-like, while others are "unbirdlike".^[8] Loud calls are useful in dense vegetation or at night where it is difficult to see another member of the species. Some calls are territorial.^[2]

Reproduction

The breeding behavior of many Rallidae species are poorly understood or unknown. Most are thought to be monogamous, although polygyny and polyandry have been reported.^[9]

Most often, there are five to ten eggs. Clutches as small as one or as large as fifteen eggs are known.^[9]

Egg clutches may not always hatch at the same time. Chicks become mobile after a few days. They will often remain dependent on their parents until fledging, which happens at around one month of age.^[3]

Rallidae and humans

Some of the larger, more abundant rails are hunted and their eggs collected for food.^[10] The Wake Island Rail was hunted to extinction by the starving Japanese garrison after the island was cut off from supply during World War II.^[11]

The Guam Rail is an example of an island species that has been badly affected by introduced species.

At least two species - the Common Moorhen and the American Purple Gallinule - have been considered pests.^[10]

Threats and conservation

Due to their tendencies towards flightlessness, many island species have been unable to cope with introduced species. The most dramatic human caused extinctions occurred in the Pacific Ocean as people colonised the islands of Melanesia, Polynesia and Micronesia, during which an estimated 750-1800 species of bird went extinct, half of which were rails.^[12] Some species which came close to extinction, such as the Lord Howe Woodhen, and the Takahē, have made modest recoveries due to the efforts of conservation organisations. The Guam Rail came perilously close to extinction when Brown tree snakes were introduced to Guam but some of the last remaining individuals were taken into captivity and are breeding well, although attempts to reintroduce it have met with mixed results.

Systematics and evolution

The family Rallidae has traditionally been grouped with two families of larger birds, the cranes and bustards, as well as several smaller families of usually "primitive" mid-sized amphibious birds, to make up the order Gruiformes. The alternative Sibley-Ahlquist taxonomy, which has been widely accepted in America, raises the family to ordinal level as the Ralliformes. Given the uncertainly about gruiform monophyly, this may or may not be correct; it certainly seems more justified than most of the Sibley-Ahlquist proposals. On the other hand, such a group would probably also include the Heliornithidae (finfoots and Sungrebe), an exclusively tropical group that is somewhat convergent with grebes, and usually united with the rails in the Ralli.

Extant (living) genera

Red-legged Crake, Rallina fasciata

Water Rail, Rallus aquaticus

Immature Spotted Crake (Porzana porzana)

Dusky Moorhen, Gallinula tenebrosa

• Himanthornis - Nkulengu Rail
• Sarothrura - flufftails (9 species)
• Canirallus (2 species)
• Coturnicops (3 species)
• Micropygia - Ocellated Crake
• Rallina - forest-rails (8 species)
• Anurolimnas (3 species)
• Atlantisia - Inaccessible Island Rail
• Laterallus (10 species)
• Nesoclopeus (1 living species, 1 recently extinct)
• Gallirallus - Austropacific rails (11-12 living species, 3-5 recently extinct)
• Rallus - typical rails (some 9 living species)
• Lewinia (3 species; sometimes included in Rallus)
• Dryolimnas (1 living species, 1 recently extinct)
• Crecopsis - African Crake (sometimes included in Crex)
• Crex - Corn Crake
• Rougetius - Rouget's Rail
• Aramidopsis - Snoring Rail
• Aramides - wood-rails (8-9 living species, possibly 1 recently extinct)
• Amaurolimnas - Uniform Crake
• Gymnocrex (3 species)
• Amaurornis - bush-hens (9 species)
• Porzana - typical crakes (13 living species, 4-5 recently extinct)
• Aenigmatolimnas - Striped Crake
• Cyanolimnas - Zapata Rail
• Neocrex (2 species)
• Pardirallus (3 species)
• Eulabeornis - Chestnut Rail
• Habroptila - Invisible Rail
• Megacrex - New Guinea Flightless Rail
• Gallicrex - Watercock
• Porphyrio - swamphens and purple gallinules (6 living species, 2-5 recently extinct; includes Notornis and Porphyrula)
• Gallinula - typical gallinules (7-9 living species, 1-3 recently extinct; includes Edithornis and Pareudiastes)
• Fulica - coots (c.10 living species, 1 recently extinct)

Additionally, there are many prehistoric rails of extant genera, known only from fossil or subfossil remains, such as the Ibiza Rail (Rallus eivissensis). These have not been listed here; see the genus accounts and the articles on fossil and Late Quaternary prehistoric birds for these species.

Pieter van den Broecke's 1617 drawing of the Red Rail of Mauritius, Aphanapteryx bonasia

Recently extinct genera

• Genus Nesotrochis - cave-rails (3 species; extinct prehistoric or later)
  • Antillean Cave Rail, Nesotrochis debooyi (Puerto Rico and Virgin Islands, West Indies) - may have survived until historic times
  • Haitian Cave-Rail, Nesotrochis steganinos (Haiti, West Indies) - prehistoric
  • Cuban Cave-Rail, Nesotrochis picapicensis (Cuba, West Indies) - prehistoric
• Genus Diaphorapteryx - Hawkins' Rail (extinct 19th century)
• Genus Aphanapteryx (2 species; extinct mid-18th century)
• Genus Cabalus - Chatham Rail (sometimes included in Gallirallus; extinct c. 1900)
• Genus Mundia - Ascension Flightless Crake - formerly included in Atlantisia; (late 17th century)
• Genus Aphanocrex - St Helena Swamphen (formerly included in Atlantisia; extinct 16th century)

The undescribed Fernando de Noronha Rail, genus and species undetermined, probably survived to historic times.

Late Quaternary prehistoric extinctions

• Genus Capellirallus - Snipe-rail
• Genus Vitirallus - Viti Levu Rail
• Genus Hovacrex - Hova-gallinule

and see genus accounts

Fossil record

Fossil species of long-extinct prehistoric rails are richly documented from the well-researched formations of Europe^[13] andNorth America, as well from the less comprehensively studied strata elsewhere:

• Genus Eocrex (Wasatch Early Eocene of Steamboat Springs, USA)
• Genus Palaeorallus (Wasatch Early Eocene of Wyoming, USA)
• Genus Parvirallus (Early - Middle Eocene of England)
• Genus Aletornis (Bridger Middle Eocene of Uinta County, USA)^{[verification needed]} - includes Protogrus
• Genus Fulicaletornis (Bridger Middle Eocene of Henry's Fork, USA)
• Genus Latipons (Middle Eocene of Lee-on-Solent, England)
• Genus Ibidopsis (Hordwell Late Eocene of Hordwell, UK)
• Genus Quercyrallus (Late Eocene -? Late Oligocene of France)
• Genus Belgirallus (Early Oligocene of WC Europe)
• Genus Rallicrex (Corbula Middle/Late Oligocene of Kolzsvár, Romania)
• Rallidae gen. et sp. indet. (Late Oligocene of Billy-Créchy, France)^[14]
• Genus Palaeoaramides (Late Oligocene/Early Miocene - Late Miocene of France)
• Genus Paraortygometra (Late Oligocene/?Early Miocene -? Middle Miocene of France) - includes Microrallus
• Genus Pararallus (Late Oligocene? - Late Miocene of C Europe) - possibly belongs in Palaeoaramides
• Rallidae gen. et sp. indet. (Bathans Early/Middle Miocene of Otago, New Zealand)^[15]
• Rallidae gen. et sp. indet. (Bathans Early/Middle Miocene of Otago, New Zealand)^[16]
• Genus Miofulica (Anversian Black Sand Middle Miocene of Antwerp, Belgium)
• Genus Miorallus (Middle Miocene of Sansan, France -? Late Miocene of Rudabánya, Hungary)
• Genus Youngornis (Shanwang Middle Miocene of Linqu, China)
• Rallidae gen. et sp. indet. (Sajóvölgyi Middle Miocene of Mátraszõlõs, Hungary)^[17]
• Rallidae gen. et sp. indet. (Middle Miocene of Grive-Saint-Alban, France)^[18]
• Rallidae gen. et sp. indet. (Late Miocene of Lemoyne Quarry, USA)
• Rallidae gen. et sp. indet. UMMP V55013-55014; UMMP V55012/V45750/V45746 (Rexroad Late Pliocene of Saw Rock Canyon, USA)
• Rallidae gen. et sp. indet. UMMP V29080 (Rexroad Late Pliocene of Fox Canyon, USA)
• Genus Creccoides (Blanco Late Pliocene/Early Pleistocene of Crosby County, USA)
• Rallidae gen. et sp. indet. (Bermuda, West Atlantic)
• Rallidae gen. et sp. indet. (fomerly Fulica podagrica) (Late Pleistocene of Barbados)^[19]

Doubtfully placed here

These taxa may or may not have been rails:

• Genus Ludiortyx (Late Eocene) - includes "Tringa" hoffmanni, "Palaeortyx" blanchardi, "P." hoffmanni
• Genus Telecrex (Irdin Manha Late Eocene of Chimney Butte, China)
• Genus Amitabha (Bridger middle Eocene of Forbidden City, USA) - phasianid?
• Genus Palaeocrex (Early Oligocene of Trigonias Quarry, USA)
• Genus Rupelrallus (Early Oligocene of Germany)
• Neornithes incerta sedis (Late Oligocene of Riversleigh, Australia)^[20]
• Genus Euryonotus (Pleistocene of Argentina)

The presumed scolopacid wader Limosa gypsorum (Montmartre Late Eocene of France) is sometimes considered a rail and then placed in the genus Montirallus.^[21]

Footnotes

1. ^ ^{a b} Horsfall & Robinson (2003): pp. 206-207
2. ^ ^{a b} Horsfall & Robinson (2003): p. 208
3. ^ ^{a b} Horsfall & Robinson (2003): p. 210
4. ^ Horsfall & Robinson (2003): p. 209
5. ^ McNab & Ellis (2006)
6. ^ McNab (1994)
7. ^ Slikas et al. (2002)
8. ^ Horsfall & Robinson (2003): p.207
9. ^ ^{a b} Horsfall & Robinson (2003): pp. 209-210
10. ^ ^{a b} Horsfall & Robinson (2003): p. 211
11. ^ BLI (2007)
12. ^ Steadman (2006)
13. ^ Mlíkovský (2002)
14. ^ A small species of rail: Hugueney et al. (2003)
15. ^ Dozens of mostly broken isolated skull and limb bones of a rail or crake the size of a Slaty-breasted or small Buff-banded Rail: Worthy et al. (2007)
16. ^ Quadrate (MNZ S.40957) and 2 femora (MNZ S.42658, S.42785) of a rail or crake the size of a large Buff-banded Rail: Worthy et al. (2007)
17. ^ Several limb bones of a smallish rail: Gál et al. (1998-99)
18. ^ Partial hand of a Common Moorhen-sized rail: Ballmann (1969)
19. ^ Storrs L. Olson: A new species of Nesotrochis from Hispaniola, with notes on other fossil rails from the West Indies (Aves: Rallidae) In: Proceedings of the Biological Society of Washington 87, 38:p 439-450, 1974
20. ^ Specimen QM F40203. A left carpometacarpus piece of a bird about the size of Lewin's Rail. Probably from a rail, but it is too damaged to determine its affiliations more precisely: Boles (2005)
21. ^ Olson (1985), Mlíkovský (2002)

References

Wikimedia Commons has media related to: Rallidae

• Ballmann, Peter (1969): Les Oiseaux miocènes de la Grive-Saint-Alban (Isère) [The Miocene birds of Grive-Saint-Alban (Isère)]. Geobios 2: 157-204. [French with English abstract] doi:10.1016/S0016-6995(69)80005-7 (HTML abstract)
• BirdLife International (BLI) (2007): Wake Island Rail BirdLife Species Factsheet. Retrieved 2007-07-04.
• Boles, Walter E. (2005): A New Flightless Gallinule (Aves: Rallidae: Gallinula) from the Oligo-Miocene of Riversleigh, Northwestern Queensland, Australia. (2005) Records of the Australian Museum 57(2): 179–190. ODF fulltext
• Gál, Erika; Hír, János; Kessler, Eugén & Kókay, József (1998-99): Középsõ-miocén õsmaradványok, a Mátraszõlõs, Rákóczi-kápolna alatti útbevágásból. I. A Mátraszõlõs 1. lelõhely [Middle Miocene fossils from the sections at the Rákóczi chapel at Mátraszőlős. Locality Mátraszõlõs I.]. Folia Historico Naturalia Musei Matraensis 23: 33-78. [Hungarian with English abstract] PDF fulltext
• Horsfall, Joseph A. & Robinson, Robert (2003): Rails. In: Perrins, Christopher (ed.): Firefly Encyclopedia of Birds. Firefly Books.
• Hugueney, Marguerite; Berthet, Didier; Bodergat, Anne-Marie; Escuillié, François; Mourer-Chauviré, Cécile & Wattinne, Aurélia (2003): La limite Oligocène-Miocène en Limagne: changements fauniques chez les mammifères, oiseaux et ostracodes des différents niveaux de Billy-Créchy (Allier, France) [The Oligocene-Miocene boundary in Limagne: faunal changes in the mammals, birds and ostracods from the different levels of Billy-Créchy (Allier, France)] [French with English abstract]. Geobios 36(6): 719–731. doi:10.1016/j.geobios.2003.01.002 (HTML abstract)
• McNab, B.K. (1994): Energy conservation and the evolution of flightlessness in birds. Am. Nat. 144(4): 628-642. HTML abstract and first page image
• McNab, B.K. & Ellis, H.I. (2006): Flightless rails endemic to islands have lower energy expenditures and clutch sizes than flighted rails on islands and continents. Comparative Biochemistry and Physiology A - Molecular & Integrative Physiology 145(3): 295-311. doi:doi:10.1016/j.cbpa.2006.02.025 (HTML fulltext)
• Mlíkovský, Jirí (2002): Cenozoic Birds of the World, Part 1: Europe. Ninox Press, Prague. ISBN 80-901105-3-8 PDF fulltext
• Olson, Storrs L. (1985): Section X.D.2.b. Scolopacidae. In: Farner, D.S.; King, J.R. & Parkes, Kenneth C. (eds.): Avian Biology 8: 174-175. Academic Press, New York.
• Slikas, B.; Olson, Storrs L. & Fleischer, R.C. (2002): Rapid, independent evolution of flightlessness in four species of Pacific Island rails (Rallidae): an analysis based on mitochondrial sequence data. J. Avian Biol. 33(1): 5-14. doi:10.1034/j.1600-048X.2002.330103.x (HTML fulltext)
• Steadman, David William (2006): Extinction and Biogeography of Tropical Pacific Birds. University of Chicago Press. ISBN 0226771423.
• Worthy, Trevor H.; Tennyson, A.J.D.; Jones, C.; McNamara, J.A. & Douglas, B.J. (2007): Miocene waterfowl and other birds from central Otago, New Zealand. J. Syst. Palaeontol. 5(1): 1-39. doi:10.1017/S1477201906001957 (HTML abstract)

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