Okinawa Rail

BirdJapan

Dec 11

Gallirallus okinawae

The Okinawa rail is Japan's only flightless bird — found exclusively on the island of Okinawa. Before nightfall, it uses its powerful clawed feet to climb trees, where it sleeps to avoid nocturnal-hunting pit vipers. In the morning, it drops back down in a graceless fluttering of wings.

For decades, an unidentified feathered cryptid ¹ lived in the forests of Okinawa. The island is part of the Ryukyu Chain, which stretches in an arc from the tip of Kyushu, Japan's southernmost large island, to Taiwan. Okinawa, lying near the middle of the arc, is the largest of these scattered isles and, with its subtropical climate, it is the southern twin to the frozen island of Hokkaido in Japan's far north. Okinawa is a land of intense sun, coral-sand beaches, and lush evergreen forests. It throngs with butterflies, lizards, and fruit bats, while migratory turtles and humpback whales bask in its warm coastal waters. One creature of Okinawa, however, long remained an enigma — existing only as a collection of recordings, photographs, and scattered feathers.

Trailing the Rail

One day in 1964, a sound recordist named Tsuruhiko Kabaya was rolling the tape on Mt. Nishime, in northern Okinawa, when he began to pick up strange sounds he'd never heard before; a medley of shrill screams and clattering laughter. These somewhat terrifying calls, Kabaya attributed to a rare, but known species on Okinawa; the Okinawa woodpecker.

Later, in the early 1970s, it was an American researcher called Dr. Lester Short who first noted a rail sighting after glimpsing a skinny, tailless, chicken-shaped bird. Dr. Short was a woodpecker expert — on Okinawa to research the bird Kabaya had supposedly recorded — and wrote off his sighting as being an already known rail which lives on the Yaeyama Islands further south.

In 1973, a bird watcher discovered a peculiar corpse. A collection of its feathers — brown and barred black and white — was preserved, labelled as an unidentified bird. Then, in 1975, a photograph was taken of the living animal and similarly labelled as an unknown bird species.

The news of this feathered mystery on Okinawa had spread as far as Tokyo, and a team from the Yamashina Institute for Ornithology set off for the island to demystify the creature. After several sightings between the years 1978-80, the researchers finally captured one adult and one youngster. Going on to successfully catch several more specimens, the team was confident that they'd uncovered a completely new species; the Okinawa rail.

Sudden Fright

Locals of Okinawa had their own names for the rail before it was ever officially described by science. Yanbaru Kuina translates to "rail that lives in this Yanbaru region", and Yamadui means "a bird of the mountains". The former name describes its range — the Yanbaru area, covering the northern third of Okinawa — and the latter describes its habitat, sort of. While the rail does live on mountains (Mount Yonaha, Okinawa's tallest mountain, at 503 metres or 1,650 ft, is within its range), it's liable to make an appearance anywhere there are trees, from sea level to the highest peaks. It also wanders into marshes and grasslands, and even cultivated fields. But the Okinawa rail is most at home in shady forests of Itaji evergreens and Ryukyu pines, in areas with dense ground foliage where it can remain hidden.

Another local name for this rail, Agachaa meaning "a sudden fright", refers perhaps to this rail's vocalisations, which could be used to score a horror scene. It cries out during the transitory periods, during dusk and dawn, or in the nighttime hours. Like a monster in the dark, it squeals and screams in a shrill voice, and its laughter-like clattering echoes through the forest. No doubt this could cause "a sudden fright" to anyone out alone at night — maybe spawning stories of monsters amidst the trees.

Or perhaps the rail frightens people with its sudden appearance and its swiftness. It's most often spotted when it crosses roads, trails, and clearings, and it's capable of sprinting at great speeds. A strange shadow, dashing across your path in the dim light, could certainly give you a sudden fright.

The Cryptid Uncovered

However, seen in the clear light of day, there's nothing much "frightening" about the Okinawa rail. Measuring around 35 cm (14 in) long and weighing some 450 grams (about a pound), the rail isn't a large bird. Its trim, ovular body is propped up on a pair of long, bright red legs. The feathers along its back are a boring olive-brown but its underside features a barred pattern of black-and-white. White streaks stream from behind each of its crimson-coloured eyes, and a bright orange-red bill draws attention to its face.

As birds go, the Okinawa rail looks a little...unfinished. It doesn't have much going on at its back end — almost completely lacking tail feathers, apart from a tiny tuft. And, as is so common with rails ², it is completely flightless — the only flightless bird in Japan. Its wings are rounded and short, too small to carry its body weight, and the muscles meant to move them are underdeveloped and weak.

The Sprinting & Climbing Rail

The loss of its flight has wound the clock back, in a way; bringing the Okinawa rail closer to its theropod dinosaur ancestors. This becomes most apparent when you look at its skeleton. The majority of the rail appears to be legs; made up of strong bones and ending in long clawed toes, four to a foot (three fore, one aft). Its wing bones, by comparison, are tiny twigs folded up to its ribcage. Its sternum and keel — to which the pectoral and wing muscles are anchored in birds — are similarly underdeveloped.

Instead, it seems that all of the rail's investment went into making those lengthy legs and a formidable bill. It uses its bill to feast on a varied forest-floor buffet; including lizards and locusts, earthworms and acorns, and, most avidly, snails. To get at their gooey insides, the rail picks them up in its bill, carries them to its favourite "snail-preparation station" (a large rock), and cracks open their shells upon it — leaving behind piles of broken snail shells from its escargots dinners.

As mentioned previously, the rail is an athletic sprinter, able to dash and weave through thick bushes as if they were incorporeal things made of smoke. But just because it's lost its flight, doesn't mean it's lost verticality. The forest is a place subdivided into layers — like the World Tree from Norse myth, each stratum of a tree, from its roots to canopy, constitutes its own realm. The Okinawa rail has learned to travel these realms without the need for wings. It becomes arboreal at night, sleeping on thick branches or sloping trunks to avoid terrestrial dangers, like the venomous habu pit viper that slithers about in the dark. As evening falls, the rail chooses a large tree, with deeply fissured bark, such as a pine or a beech. It then grasps onto the trunk with its considerable toes, digging into the crags and crevices with its ivory claws, while its muscled legs carry it upwards, a step at a time. The next morning, it gracelessly flutters back down to the ground with a flurry of its undersized wings.

Child Endangerment

While an adult rail can avoid predators by climbing, its eggs and chicks are left exposed to the dangers that lurk after dark. The Okinawa rail is a ground-nester; constructing a no-nonsense nest made of some loose leaves and grasses, and (between late March and June) plopping down 4 to 5 pale, brown-speckled eggs. These hatch into a posse of black, furry-feathered chicks that can stumble about on their tripod-like legs soon after hatching. Both parents care for their young, but there's little they can do against a sneaky pit viper and, all too often, habu snakes slink off with a mouthful of eggs or an unfortunate chick.

Why doesn't the rail adopt (or re-adopt) a tree-nesting strategy? The rail and habu have likely evolved alongside one another, so why would the rail allow its nest to be so vulnerable? Good question. Perhaps ground nests, camouflaged amidst leaf litter and foliage, actually have a lower rate of predation than more exposed arboreal nests. Perhaps this is just a win for the habu in an evolutionary arms race.

An Invaded Haven

A small Indian mongoose (*Urva auropunctata*) on Okinawa Island.

The habu doesn't only menace rails. The humans of Okinawa were also none too happy sharing an island with potentially deadly serpents. Their solution came in the form of a belligerent and voracious mammal known as the small Indian mongoose.³ In 1910, seventeen mongooses were caught in India, abducted, and deliberately released in Naha City in southern Okinawa Island. They killed and bred and spread; moving northwards, eventually reaching the Yanbaru Forest in the 1990s.

Nominally, they were there to exterminate pit vipers and pests like rats. This might have benefited the Okinawa rail — if the mongooses stuck to their intended targets. But, of course, they did not. The small mongooses ate everything; from other mammals to native reptiles to bird eggs. Not even adult rails were safe in the trees.

The mongoose was just too deadly a hunter — that's why it was introduced, after all. The rail was in real danger of disappearing as a result of human actions, before we even knew it existed. This wouldn't be the first time for a rail species either. On the isolated volcanic island of Ascension, in the South Atlantic, there once lived an endemic species of rail. Little was known about the bird — some fossils, a sketch, and a short description — before it likely perished in the 18th century following the introduction of rats, and if not then, it surely didn’t survive long after 1815, when cats were introduced to the island.

A couple of feral cats on Okinawa Island.

In addition to mongooses, the island of Okinawa has long had a sizable population of feral cats. The Okinawa rail evolved in a world where the only danger slithered along the ground at night and climbing a tree could extricate it from any such threats — Okinawa is absent of the native foxes or weasels, that are present on mainland Japan. The rail wasn't ready for tree-scaling carnivores; ones that can hunt both day and night (mongooses) as well as the hours in between (cats). The elusive Okinawa rail, once near-entirely nocturnal, was forced to shift its habits towards diurnal activity, only to encounter the feral dogs that hunted by day. It was an attack on all fronts, by an army of invading mammals.

At the time of the species' discovery, the estimated number of Okinawa rails was 2,000 individuals. By 2005, less than 25 years later, the population had fallen to some 700 rails and it was designated a 'critically endangered' species. Meanwhile, the mongooses on Okinawa Island numbered around 30,000.

A Future for the Rail

The evidence was clear; the Okinawa rail would spiral into extinction if things continued as they were. The first course of action was to prevent the mongoose swarm from moving further north, and then eliminate them from the Yanbaru area altogether. Employing 'capture-based control measures', the current goal is for all areas north of the SF Line to be mongoose-free by 2026.

What about the cats? Between 2004 and 2018, around 1,400 stray cats were housed and transferred out from the rails range. Domestic cats were fixed and microchipped, and a public awareness campaign sought to prevent the occurrence of more stray cats and dogs — as well as promote responsible cat ownership, since even some pet cats are known to hunt daily in the Yanbaru Forest.

These efforts bore fruit; a reduction in invasive hunters gave the rail some breathing room. To further bolster the rail population, a captive breeding and egg-hatching program was begun by the Okinawa Wildlife Foundation. There were several hurdles along the way — achieving artificial insemination, finding the right incubation temperature for the eggs, and maintaining genetic diversity within a breeding population of 80 rails — but in 2019, two birds from the program were released and each formed a pair with a wild individual and bred successfully. It may seem a small victory, but for a species that once teetered on the edge of extinction, it's a hopeful start.

Humans and Rails

In the caves of southern Okinawa, 20,000-year-old fossils have been uncovered; remnants of the Okinawa rail. The species probably once lived across the entire island before human development reduced its population and pushed it into the more secluded areas of the northern forest. Humans were the first invasive mammals to displace the rail from its home. Indeed, the increasing network of roads that crisscross Okinawa today may pose a larger threat to the rail than any cat or mongoose. A public awareness campaign — aiming to "highlight road-kill hotspots and encourage drivers to reduce speeds in Yanbaru" — successfully lowered the annual number of roadkill for the two following years. However, the fatalities still fluctuate year to year, and the issue is an ongoing one. Without continued community support, the Okinawa rail will once more be victim to too many careless accidents.

A giant statue of the Okinawa rail at Cape Hedo, which doubles as an observatory deck.

Some locals of Okinawa have passionately embraced their unique rail. The village of Kunigami, for example, has adopted the Yanbaru Kuina (the local name for the rail) as the symbol of their village — quite literally, as it features in the village's logo. The rail also offers farewell to visitors, with a sign reading: “You’re welcome again to Kunigami, the village of the Yanbaru Kuina”. September 17 sees the celebration of ‘Yanbaru Kuina Day’, with the ‘Kuina Festival’ featuring "guided walks, eco-activities, arts and crafts and an appearance by Kui-chan, the Yanbaru Wildlife Conservation Center mascot". Visitors to the village can also buy doughnuts (a local speciality), with packaging that features two rails sharing the same sweet treat. Afterwards, they can trek north of Kunigami, to Cape Hedo, and climb the giant statue of an Okinawa rail that doubles as an observatory deck.

There is an obvious love and appreciation for the rail here and Okinawans have made a concerted effort to save the species. In July of 2021, the Yanbaru Forest was registered as a UNESCO natural heritage site for its abundance of unique flora and fauna — the Okinawa rail chief among them. No doubt this will help preserve the rail's remaining bastion of habitat. The species' conservation status has been reassessed by the IUCN since conservation efforts began; improving from 'critically endangered' to 'endangered. One figure from 2019 put the total population at 1,500 birds — a marked increase from 700 in 2005 — however, as of its 2020 IUCN assessment, the total number of mature rails sits at 480 individuals, and the population trend is decreasing. The Okinawa rail currently teeters on a precarious ledge; between a hopeful future and a decline back into jeopardy. With some help, the rail can use its powerful legs and grasping toes to climb onto a safe and stable branch.

A tiger keelback snake (*Rhabdophis tigrinus*) on top and a *tsuchinoko* on the bottom.

¹ Japan has its own culture of cryptozoology, although in Japan, rather than being called cryptids, the elusive creatures of doubtful existence are known as UMA (Unidentified Mysterious Animals).

Perhaps the most famous UMA is the tsuchinoko. Its name literally translates to “mallet/hammer child”, and it supposedly looks like an abnormally stocky snake. It's not some giant monster — it's only as long as your average grass snake — it just has a very girthy midsection, as if it swallowed something much too large.

Perhaps this element of plausibility is what kicked off the “tsuchinoko boom" in the 1970's, when this UMA reportedly began popping up all over Japan. The hunt was on. Several sightings and indistinct photographs were put forth as evidence of its existence until a farmer in rural Okayama Prefecture stumbled upon the remains of a corpse. Newspapers, magazines, and television shows flocked. Then a biologist was brought in. His verdict: it was "probably a yamakagashi — a tiger keelback snake (Rhabdophis tigrinus) — but not a normal one". Perhaps its last meal was a particularly ambitious one, leading to an untimely end and an overstuffed body.

From top to bottom; a South Island takahē (*Porphyrio hochstetteri*), Lord Howe woodhen (*Hypotaenidia sylvestris*), and Inaccessible Island rail (*Laterallus rogersi*).

² Rails have a tendency to stop flying. This bird family (Rallidae) contains some 40 living species and many of them are either completely flightless or nearly so. Most go about losing their flight in the same way the Okinawa rail did — they fly to an isolated island, settle down in an ecosystem with no ground predators, and, with predation pressure lifted, they have no reason to continue making the heavy investments required for flight, and over generations, the ability degrades.

Today, flightless rails are found from New Zealand (South Island takahē) to Australia's Lorde Howe Island (Lord Howe woodhen) to New Caledonia (New Caledonia rail) further north, to the other side of the world in the South Atlantic, on Inaccessible Island (Inaccessible Island rail). The rails have also suffered, at the hands of humans, more than any other living family of aves. In the past 400 years, humans have caused the extinction of at least 26 rail species.

You can read more about the evolution of flightlessness and rails (living and extinct) here!

³ This same species, the small Indian mongoose has been introduced to over 60 islands worldwide for the same purpose — exterminating pests. From Okinawa, the mongoose was (in 1979) brought to a Japanese island to the northeast called Amami Ōshima. However, with great effort, it has since been removed completely from the island. But that is a story best told by an Amami Ōshima endemic bird; Lidth's jay.

**Where Does It Live?**

⛰️ Evergreen and broadleaf subtropical forest with dense undergrowth.
📍 Yanbaru Forest, in the northern part of Okinawa Island in the Ryukyu Islands of southern Japan.

‘Endangered’ as of 13 August, 2020.

IUCN

Size // Small
Wingspan // 48 - 50 cm (18.9 - 19.6 in)
Length // 30 - 35 cm (11.8 - 13. 8 in)
Weight // 435 g (~1 lb)
Activity: Diurnal/Nocturnal ☀️/🌙
Lifestyle: Solitary 👤
Lifespan: N/A
Diet: Omnivore
Favorite Food: Snails 🐌
Class: Aves
Order: Gruiformes
Family: Rallidae
Genus: Hypotaenidia
Species: H. okinawae

There have long been rumours of a cryptic creature living in the forests of northern Okinawa Island. A sound recording in 1964, a sighting in the early 70s, a corpse in '73 and a photograph in '75 — for years the creature eluded capture. Eventually, this mystery attracted the attention of an ornithological research institute in Tokyo. A team from the institute officially confirmed the creature's existence in 1978 and after catching several live specimens, it was described as an entirely new species to science; the Okinawa rail.

The Okinawa rail lives only on a single island; Okinawa Island — a part of Japan's southern Ryukyu Island Chain. On this subtropical island, the rail inhabits the Yanbaru area, which covers the northern third of Okinawa, more specifically in the Yanbaru Forest.

To escape dangerous nocturnal predators, like the local habu pit viper, the rail uses its powerful legs and toes to climb trees — since it cannot fly — where it sleeps out the night.

While adults escape to arboreal safety, their eggs remain on the ground in nests of loose grasses and leaves — and probably in some considerable danger. The fuzzy black chicks that do hatch soon begin to stumble about after their mum and dad, who both care for the young.

One local name for the Okinawa rail, Agachaa, translates to "a sudden fright". Although the rail itself isn't very scary — only being some 30 cm (11.8 in) long — its habit of sprinting suddenly across paths and roads, or crashing out of trees in the morning, might be startling enough to inspire the nickname. Alternatively, its calls, which sound like shrill screams and clattering laughter, might be its most frightening feature.

The rail eats a varied forest-floor diet, but it's particularly fond of snails. It brings them to a large rock, upon which it cracks open their shells, and then eats their gooey insides. Broken shells often pile up near these escargot dining sites.

20,000-year-old fossils of this rail have been uncovered in southern Okinawa, suggesting that the species once ranged across the whole island, but has since been pushed into the wilder north.

While the island of Okinawa is naturally absent of mammalian predators like foxes and weasels, humans have introduced stray dogs, feral cats, rats, and, more recently, mongooses.

Seventeen small Indian mongooses were intentionally released onto Okinawa Island in 1910, in a bid to combat the invasive rodents and native pit vipers. The mongooses reached the rail's last hideout, the Yanbaru Forest, in the 1990s, with populations peaking at around 30,000 mongooses.

Faced with nocturnal predators that it had no defences against, the once exclusively nocturnal rail started becoming increasingly diurnal, only to encounter the feral dogs that hunted by day.

Another threat to the rail is that of becoming roadkill. The increasing number of roads, coupled with the rail's need to cross them, has caused not a few accidents.

At the time of the Okinawa rail's discovery, the estimated number of individuals was 2,000. By 2005, less than 25 years later, the population had fallen to some 700 rails and it was officially designated as a 'critically endangered' species. As of a 2020 IUCN assessment, the total number of mature rails sits at 480 individuals and is believed to be decreasing.