Blakiston's Fish-Owl

BirdEast Asia

9 Apr

Written By Alexander Julius Jensen

Ketupa blakistoni

Blakiston's fish-owl is one of, if not the largest owl species in the world, with a wingspan reaching 2 metres (6.6 ft) and a weight exceeding 4 kilograms (8.8 lb). It is endangered — it's estimated that less than 2,000 individuals hunt the cold rivers of northeast Asia.

The Owl

On the branch of an ancient oak, overlooking a stretch of ice-banked river, perches a large, stooping shape. This creature is a fierce hunter, a bird-of-prey, but it looks like a big mound of fluff. Its plump, barrel-shaped body is dressed in a winter coat of dark and light brown plumage, barred and streaked, made from thick layers of the softest feathers. This individual is particularly large — a female — perhaps 70 centimetres (2.3 ft) from top to bottom. Her perch must be solid, for she can weigh upwards of 4 kilograms (8.8 lb).¹

Two tufts of feathers adorn her head — which can variably be seen as ears, eyebrows, a crown, or something like the ornaments on a samurai's helmet. For an owl, her head seems small, as she lacks the prominent facial disk of a great grey or barn owl, which they use to funnel sound into their ears. But her senses aren't lacking. Her large yellow eyes, immobile in her skull, pierce the settling darkness and her hearing is sharp enough to cut through the noise of the rushing river below.

Her feet are bare — unusual for an owl, most of whom have feathered "boots" — with spiky scales lining the underside of her toes, each of which terminates in an exceptionally long and black talon. Her feet provide an excellent grip on her perch, but they're meant for grasping more than wood.

The Hunt

Through the darkness of night, over the tumult of water, she spies a potential target. Shifting her great feathery mass, she unfurls her wings to a span of 2 metres (6.6 ft), and glides down towards the river, bearing her black talons.

Her descent isn't the silent glide of most owls. The leading edge, where air meets wing, of a snowy or barn owl is lined with comb-like, serrated feathers which smoothly guide airflow over the wing, across velvety feathers, and past the fringed end feathers — their combined effect dampening the sound of an owl’s glide to near silence.² These are the tools of a stealthy, ambush hunter; of a snowy owl hunting lemmings beneath the snow, a tawny owl plucking voles from the forest floor, or a Ural owl drifting soundlessly to snatch a young hare. Their sharp-eared prey would hear them fluttering in for the kill, and could potentially escape, if the owls weren't as silent as they are.

But our giant huntress has no need to be quiet. She is a fish-owl; her prey is currently swimming through the river currents, all but deaf to the world above the surface. Although her wings, lacking silencing feathers, flutter and woosh, the fish can't hear her anyway — she is Death, barreling towards them on not-so-silent wings. But Death stops just short of the water's edge, alighting on a fallen log, half-submerged in the water. From this "fishing platform," she scrutinizes the shallows illuminated by the glowing moon above, until she spots a fish that’s to her liking — perhaps a grey-pink salmon or trout, a small stone loach hiding amidst the gravel, or even an eel-like lamprey — and she makes a final, fatal hop into the river.

As her outstretched feet plunge into the icy water, she sweeps her open wings upwards, forming an arc overhead and displaying her barred flight feathers. Her naked toes close around her target, the spiny texture of her feet seizing against her prey's slippery scales just before her black talons sink into its flesh. Her long legs keep her dry as she stamps down, pinning her prey against the river's bottom. Then, with a few laborious flaps she lifts from the water, clutching her catch in one foot, and settles onto the snowy shoreline. From foot to beak she transfers her prey — a char, sleek with white spots — and swallows it whole, head first, right then and there.

She has been lucky tonight. Snatching slippery prey from a dark, flowing river isn't easy and usually requires some splashing and prancing around in the cold, shallow water. If the river yields no prey, she's not above scavenging. She might follow a pair of crested ibises — wading birds with naked red faces and long decurved bills — to pick at the remains of dead fish they leave behind.

She hunts now while she still can, for when winter comes, most of the rivers will be sealed under a layer of ice. During the season of harshest cold — with average winter temperatures of -19 to -38 °C (-2 to -36 °F), and sometimes falling as low as -68 °C (-90 °F) — she is deprived of her primary source of food. She must scrape by, hunting small mammals and waterfowl in spite of her “noisy” wings. If she makes it through the long cold and dark, if she survives the hunger of winter to see the start of spring, she'll witness the waterways thaw and flow once more with fish, their banks hopping with an abundance of frogs on which she will happily dine. And as winter breathes its last few frozen breaths, and dusk falls on a new night, resonating calls echo across the landscape, sung in a deep voice ("boh, boh"). She takes up her part in response ("boh"), singing a duet with her lifelong partner.

Parenthood

Her mate is a smaller male. His two-note call, slightly higher pitched, is immediately followed by the female's response, a single deeper note — alternately, they might each hoot a single note in quick succession — making their duet sound like a practised solo sung by a single bird. Together, they compose a resonant chant that can be heard more than a kilometre away, travelling well over the sound of moving water. Across their vast domain of ancient trees and seabound rivers, no barrier separates them, even when they're out of one another's sight.

Their home is a giant elm tree, its trunk over a metre in diameter, its broad canopy snaking some 30 metres (100 ft) skywards. It is grizzled and ancient. Although its body is still strong, it's lost many limbs throughout the 100 or so years it's been alive, leaving it full of holes. It's in one of these hollows — a woody cavern a metre (3.3 ft) wide — where the pair have made their nest. Inside, the female laid two white eggs as winter slackened its grip at the tail-end of February. A bit over a month later, the eggs hatched into little cotton balls on legs. The mother now stays with them during the day, keeping them safe and warm. The father, meanwhile, goes out to hunt — bringing back slippery fish and crunchy crawfish and not a few frogs — which the mother tears into manageable pieces for their chicks. The hungry nestlings, screeching for their food ("Bie-, bie-"), grow larger by the day.

Clockwise from top left; a Blakiston’s fish-owl in a tree hollow nest, a juvenile Blakiston’s fish-owl, and a young Blakiston’s fish-owl chick next to an egg.

A month later, only one of the two chicks — the stronger one — remains. She is much bigger now, and her white hatchling feathers have been replaced by ashen plumage, although her coat is still mostly fuzzy down. The skin around her eyes is bare and black. With her “greying hair” and “dark eyebags”, she looks more haggard and elderly than her adult parents. She'll stay in their nest for another month, during which time her bare facial skin sprouts into a mask of black feathers and finally into the white one of an adult, and she'll moult her fuzzy feathers, growing in her adult plumes capable of flight. She has finally fledged, and the vast world outside the nest has been opened to her. But it is a harsh world. Although she can fly, she'll stay with her parents, and they'll continue to feed her as she makes her first hunting attempts: fumbling about in the water, slipping over slippery rocks, trying to grab slippery fish. Only with the onset of her first winter will she be forced to fully feed herself — even then, she'll remain in her parents’ territory until the following spring. Only when she’s ready to be fully self-sufficient, and find a mate for herself will she fly off to find a territory of her own.

With their daughter gone, the parents may not breed for another year or two, but they'll stay together through each frozen winter and probably for the rest of their lives — until one of them dies, at least. Over the next five years, even though their daughter has her own mate — and has become a mother herself — she will repeatedly return to her birthplace, and her parents will recognise her as the white fluffball, tiny and helpless, that they once raised in their nest.³

Generations

A Blakiston's fish-owl may live for over 20 years in the wild. The forest in which it lives is over 200 years old. The individual oaks, elms, and poplar trees here are many decades old, if not centuries. As they’ve laid down new rings, one every summer of their long lives, their trunks have grown massive, while time and decay have left them scarred with immense hollows — large enough for a family of the world's largest owls. However, another animal, more powerful than the owl, claims these same trees as its own; not to take up residence, but to slash and topple, and turn the wood of the old-growth trees into prime lumber. That animal, of course, is us.

Since the start of the new millennium, Russia has lost 11% of its total forest cover. In 2018, its rate of deforestation outstripped that of Brazil by some 2.6 million hectares (6.4 million acres). A considerable portion of that deforestation is illegal, but it occurs in out-of-reach places, such as the Russian Far East and along the Russian-Chinese border — home of Blakiston's fish-owl.

Blakiston's fish-owl is a large predator. Just as its neighbour, the Siberian tiger, needs large tracts of forest for hunting deer and boar, the owl needs a large territory for hunting fish — with the domain of a single owl pair spanning a 15-kilometre (9-mile) stretch of river. Without trees, the owl loses its hunting perches. Without their roots, soils become loose and wash into the rivers, clouding the water and clogging the beds where fish spawn. Prey is made more scarce, and hard hunting is made harder. Left behind in the aftermath of large-scale logging are small fragments of old-growth forests, and they just aren't enough for these apex predators to survive. Even if the owls could scrounge enough food to get by, it would scarcely matter in the long run if prospective parents — with their nesting trees gone — have nowhere to raise their fluffy, white chicks.

The range of Blakiston's fish-owl extends beyond the mainland; across the narrow Strait of Tartary to the Russian island of Sakhalin and, from there, southwards across another strait, La Pérouse Strait, reaching Japan's northernmost island of Hokkaido. To the Ainu, the indigenous people of Hokkaido, this giant owl is Kotan-kar-kamuy (the “god that protects the village”), and is believed to bring luck in hunting and fishing, and is a symbol commonly seen in Ainu art. As the owls bring them protection and fortune, the Ainu believe humans have a responsibility towards these owl-deities, and through them, the entire natural world.

The deforestation on Hokkaido has been much less than that on the mainland — the island lost 0.70% of its forest cover from 2000 to 2020 — but, even so, the effects of timber harvesting, exploitation of river fish, and human development have shrunk the range of Blakiston's fish-owl. The very first type specimen for this species was collected by Thomas Blakiston in 1883 near the city of Hakodate, near the southern tip of Hokkaido. During Blakiston's time, the owl ranged from that southern point, north to the capital of Sapporo, and east to Obihiro. Today, it's mostly restricted to the more sparsely populated far eastern parts of the island — the feathered god of fortune and protection has been evicted from our modern-day dwellings. Some seek to bring it back.

Restorations

Nesting sites, food availability, and the survival of fledglings — these are the three major factors that must be addressed if the owls are to survive, or maybe even, one day, flourish again. More than 200 nesting boxes have been constructed across Hokkaido as replacements for the tree cavities that are no longer present or are too few in number. Feeding projects provide fish to nesting pairs — at one of the nesting sites, provisioned fish accounted for more than 90% of the food weight fed to chicks. And, when those chicks do fledge, they are banded in order to track their growth and health, and collect data on the population as a whole, making it possible to assess how successful such conservation efforts actually are.

Hokkaido has seen a slow and steady improvement in the numbers of Blakiston's fish-owls. In the 1970s, there were estimated to be only 70 owls across the entire island. Today, that number has doubled to around 165 individuals. Admittedly, that's still not a very high number, but it's a move in the right direction — which is more than can be said for many endangered species. And the Blakiston's fish-owl is still considered endangered. The vast majority of its population — between 1000 and 2,500 individuals — live on the mainland. There have been efforts to save the species in the Russian Far East, partially chronicled in the book Owls of the Eastern Ice by Jonathan C. Slaght, who’s been working with logging companies in Primorye, Russia, to protect the most valuable old-growth forest — using insights from his years gathering invaluable data on the owl's feeding, breeding, and habitat requirements — and has expanded protected habitat from 19% to over 60% within the fish-owls range.⁴

As it stands today, many fish-owls are heavily reliant on the labour-intensive work of conservationists. Given the current dire situation, such actions are necessary. But, in the long run, the goal is a population that can sustain itself within a sufficient habitat, without the need for artificial nests and food handouts. Restoring that habitat takes effort — gathering data, creating a plan, and turning that plan into a legal policy — and, given the nature of old-growth forests, it also takes time. Do the fish-owls, or we humans for that matter, have that time?

A globally warming climate necessarily affects the entire world, with different consequences for each ecosystem and community. The Arctic loses its sea ice, the high alpine habitats of the Himalayas are pushed ever higher, and corals of the Great Barrier Reef are bleached in a too-warm ocean, as the adjacent landmass dries and burns, all as lowlands worldwide are submerged beneath rising seawater. For Blakiston's fish-owl, the consequences of climate change are a trophic mismatch — spring arrives unpredictable, bringing its bounties (namely frogs) either too early or too late for the owl's nesting chicks, who go underfed and starve — as well as increasingly destructive storms that topple what old-growth trees remain, bringing the sheltering owls and their chicks down with them. Giving the fish-owl its forests and rivers back is critical, but if the seasons leave it behind, if extreme weather devastates its habitat, it may face extinction regardless.

Is there a future for these largest of owls? One where they haunt ancient forests, sheltering in their cavernous tree hollows, and hunt rivers that run with fish and hop with frogs? That depends on what we, humanity, do about the most widespread and pressing challenges of the current day; the most difficult challenges that we've ever had to face as a species. Challenges for which we must take responsibility, in both senses — the blame, yes, but also the duty to do something about them.

¹ Does 4 kilograms seem underwhelming for an animal holding the title of "the largest of its kind"? Birds — with their hollow bones, lightweight beaks and feathers, and internal air sacs— are, in general, light for their size.

The great grey owl strikes an imposing figure; at up to 84 cm (2.7 ft) tall, it exceeds Blakiston's owl in height. Its maximum weight? Not even 2 kg (<4.4 lb). It seems that the vast majority of its bulk is made up of feathers, which don't weigh very much. The Eurasian eagle-owl is shorter but can weigh twice as much, with a maximum weight of 4.2 kg (9.2 lb) — still short of Blakiston's record weight of 4.6 kg (10.1 lb). At the opposite end of the scale, the elf owl — the world's smallest owl — is about the size of a sparrow and has a maximum weight of 55 grams (1.9 oz).

² The gliding flight of a barred owl, for instance, is inaudible to human ears until it flies within a range of 3 metres (9.8 ft). The owl's silencing adaptations can reduce the noise of its flight by as much as 10 decibels — to get an idea of the noise reduction; if a falcon (lacking stealthy wing structure) is akin to a passing truck, then the owl is more like a passing car.

Other fish-owls, like the tawny fish-owl, either have narrower combs, or no combs at all along the leading edges of their wings — which would make sense, given the auditory insensitivity of their prey. The same goes for primarily insect-hunting owls like the burrowing owl.

³ Some female Blakiston’s fish-owls, upon returning to their natal sites, won't leave again. There was one five-year-old female in Hokkaido who returned right after her mother had disappeared. In a taboo twist, she then paired with her own father and remained with him for 12 years. Then, after her father/partner disappeared, she paired with her own grandson and successfully raised two broods with him. This might be one of those situations where we reserve our human value judgments in the face of an animal’s questionable behaviour.

⁴ The book — Owls of the Eastern Ice: A Quest to Find and Save the World's Largest Owl — is a great case study on conservation and all of the on-the-ground work required in the efforts to save an endangered species. From Slaught's website: "I work with Sergey Surmach and Sergey Avdeyuk every year to find Blakiston’s fish owls and preserve their habitat. All of our activities are grant- and gift-based."

If you want to contribute to their efforts, you can do so here!

**Where Does It Live?**

⛰️ The Russian Far East, Hokkaido in Japan, and parts of northeastern China.
📍 Old-growth, riverine forests.

‘Endangered’ as of 01 October, 2016.

IUCN

Size // Medium
Wingspan // 1.8 – 2 metres (5.9 – 6.6 ft)
Height // Up to 75 cm (2.4 ft) tall
Weight // 3 – 3.7 kg (6.6 – 8,1 lb) for males, up to 4.5 kg (9.9 lb) for females
Activity: Nocturnal 🌙
Lifestyle: Solitary 👤/ Pair 👥
Lifespan: Likely 20 years or more
Diet: Primarily fish like pike, catfish, trout, and salmon
Favorite Food: Fish 🐟
Class: Aves
Order: Strigiformes
Family: Strigidae
Genus: Ketupa
Species: K. blakistoni

Blakiston’s fish owl is the largest owl species in the world by mass, with some females weighing up to 4.6 kilograms (10.1 lb) and sporting a wingspan of up to 2 metres (6.6 feet).

It inhabits old-growth riverine forests in the Russian Far East, Hokkaido in Japan, and parts of northeastern China, where it hunts along rivers. The territory of a single owl pair can span a 15-kilometre (9-mi) stretch of river.

Unlike most other owls, this fish-owl lacks the wing structures that make flight silent. Its primary prey — fish, including salmon, trout, and lamprey — can't hear it coming anyway.

When hunting, Blakiston's fish-owl stands still at the edge of a river or wades in shallow water, then lunges to catch fish with its powerful talons. Its toes are bare, not feathered like most owls, and covered with rough spines to help it grip slippery prey.

Pairs are lifelong and territorial, communicating with deep, resonant duets ("boh") that echo across frozen valleys and can be heard several kilometres away, travelling well over flowing water.

Their breeding and nesting require massive, old trees. Nests are made in natural hollows — woody caverns a metre (3.3 ft) wide — that take decades to form.

In Japan, only about 200 breeding pairs remain. Blakiston’s fish owl is classified as Endangered and remains a symbol of vanishing wilderness.

The female lays 1–2 eggs in a large tree hollow, typically in February or March, and incubates them alone for about 35 days while the male brings her and the chicks food (a lot of frogs during spring). Because the first egg hatches earlier, the older chick often grows much faster and outcompetes its sibling. In years of scarce food, the second chick usually dies.

A young, unfledged Blakiston's fish-owl wears a downy coat of grey feathers, with bare black skin around its eyes — appearing more elderly and haggard than its adult parents.

Even after fledging, young owls depend on their parents for several months, gradually learning to hunt and fly as they explore the river corridors. Juveniles may remain in their parents' territory for over a year before going off to claim a domain of their own.

Even after establishing a territory, finding a mate, and having children, an owl might repeatedly return to its birthplace and parents.

The species is named after Thomas Blakiston, an English explorer and naturalist who, in 1883, collected the first type specimen of the world's largest living owl.

Today, this owl no longer lives in the area where its first specimen was collected. In Japan, only about 200 breeding pairs remain. The vast majority of its population — between 1000 and 2,500 individuals — live on the mainland. Blakiston’s fish owl is classified as an endangered species.