Tawny Fish Owl
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The tawny fish owl (''Ketupa flavipes'') is a fish owl
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
in the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
known as
typical owl The true owls or typical owls (family (biology), family Strigidae) are one of the two generally accepted families of owls, the other being the barn owls and bay owls (Tytonidae). This large family comprises 230 living or recently extinct species ...
s, Strigidae. It is native from southern Nepal to
Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...
, Vietnam and
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
and Bhutan. Due to its wide geographical distribution, it is listed as
Least Concern A least-concern species is a species that has been evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...
on the
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...
.


Taxonomy

''Cultrunguis flavipes'' was the
scientific name In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
proposed by
Brian Houghton Hodgson Brian Houghton Hodgson (1 February 1801 – 23 May 1894) was a pioneer natural history, naturalist and ethnologist working in India and Nepal where he was a British Resident (title), Resident. He described numerous species of birds and mammals fr ...
in 1836 who described a yellow-footed fish owl from
Nepal Nepal, officially the Federal Democratic Republic of Nepal, is a landlocked country in South Asia. It is mainly situated in the Himalayas, but also includes parts of the Indo-Gangetic Plain. It borders the Tibet Autonomous Region of China Ch ...
. ''Ketupa'' was proposed as
generic Generic or generics may refer to: In business * Generic term, a common name used for a range or class of similar things not protected by trademark * Generic brand, a brand for a product that does not have an associated brand or trademark, other ...
name by René-Primevère Lesson in 1831 for fish owl species from
Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...
and
India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
. Results of a
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
analysis of nine
horned owl The Americas, American (North and South America) horned owls and the Old World eagle-owls make up the genus ''Bubo'', at least as traditionally described. The genus name ''Bubo'' is Latin for owl. This genus contains 10 species that are found i ...
species indicate that ''Ketupa'' species form a
monophyletic group In biology, a clade (), also known as a monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach to taxonomy ...
.


Description

Like other fish owls, the tawny fish owl has large ear tufts but they usually hang to the sides of the head and are distinctly messy and tousled looking. They have yellow eyes. Tawny fish owls have been described as the most "attractive" of the fish owls.Hume, R. (1991). ''Owls of the world''. Running Press, Philadelphia, PA. 1991. They tend to be an orangey-rufous color on the crown and upperparts, which are overlaid with broad, blackish markings on the central part of the feathers and spots of the same color as the reddish-brown feather edges. The scapulars are a dingy yellow color, forming a contrasting band which runs across the owl's shoulders. The flight and tail feathers are strongly barred dark brown and buffish. The facial disc is poorly defined but a sizeable off-white area on the eyebrows and forehead stands out. While buffy and brown fish owls are featherless on their legs and the
Blakiston's fish owl Blakiston's fish owl (''Ketupa blakistoni''), the largest living species of owl, is a fish owl, a sub-group of eagle-owls that specialize in hunting in riparian areas. It is native to China, Japan, and the Russian Far East. This species is a p ...
(''Ketupa blakistoni'') has totally feathered legs (the latter more like most ''Bubo''), the tawny fish owl has feathering over two-thirds of the tarsi. The legs below feathering are greenish-yellow with greyish-horn coloured talons. Beside the variability of the feathering of the legs, the buffy fish owl is most similar in plumage but is smaller and buff hued rather than orange-rufous hued. The brown fish owl is a much more solid brown color with distinct vermiculations below and no yellowish band across the back. Compared to eagle owls of similar length, fish owls tend to be even shorter in tail length and even heavier in build, have relatively larger wings (the tawny and Blakiston's being particularly chunky in shape), have considerably longer legs, and have a rough texture to the bottom of their toes. At least the latter two features are clear adaptations to aid these owls in capturing fish. Diurnal raptors who feed largely on fish have similar, if not identical, rough texture under their toes, which helps these birds grasp slippery fish. Unlike diurnal raptors who capture fish such as the osprey (''Pandion haliaetus'') as compared to most terrestrial raptors, the fish owls have large, powerful, and curved talons and a longitudinal sharp keel sitting under the middle claw with all having sharp cutting edges that are very much like those of eagle owls. Also, unlike many fish-eating diurnal raptors, fish owl will not submerge any part of their body while hunting, preferring only to put their feet into the water, although fish owls will hunt on foot, wading into the shallows. Unlike most owls, the feathers of fish owls are not soft to the touch and they lack the comb and hair-like fringes to the primaries, which allow other owls to fly silently in order to ambush their prey. Due to the lack of these feather-specializations, fish owl wing beats make sounds. The lack of a deep facial disc in fish owls is another indication of the unimportance of sound relative to vision in these owls, as facial disc depth (as well as inner ear size) are directly related to how important sound is to an owl's hunting behavior. Similar adaptations, such as unwillingness to submerge beyond their legs and lack of sound-muffling feathers are also seen in the African fishing owls, which do not seem to be directly related. Tawny fish owls are around the same size as the brown fish owl in terms of linear dimensions. The tawny is long from bill to tail. However, studies have revealed the tawny is surprisingly rather heavier on average than the brown fish owl and, less surprising, is considerably heavier than an
eagle owl The American (North and South America) horned owls and the Old World eagle-owls make up the genus ''Bubo'', at least as traditionally described. The genus name ''Bubo'' is Latin for owl. This genus contains 10 species that are found in many pa ...
of comparable length. Six adult tawny fish owls were found to weigh an average of , with a reported range of , and are thus one of the heaviest living owl species. Only the Blakiston's fish owl and a majority of races of
Eurasian eagle owl The Eurasian eagle-owl (''Bubo bubo'') is a species of eagle-owl, a type of bird that resides in much of Eurasia. It is often just called the eagle-owl in Europe and Asia. It is one of the largest species of owl. Females can grow to a total ...
(''B. bubo'') are heavier on average. The maximum (not average) weight of
Verreaux's eagle owl Verreaux's eagle-owl (''Ketupa lactea''), also commonly known as the milky eagle owl or giant eagle owl, is a member of the family Strigidae. This species is widespread in sub-Saharan Africa. A member of the genus ''Ketupa'', it is the largest Af ...
s (''Ketupa lactea'') and
snowy owl The snowy owl (''Bubo scandiacus''), also known as the polar owl, the white owl and the Arctic owl, is a large, white owl of the true owl family. Snowy owls are native to the Arctic regions of both North America and the Palearctic, breeding mo ...
s (''B. scandiacus'') are also higher but those species have far larger sample sizes of body mass.Dunning, J.B. (2008). ''CRC Handbook of Avian Body Masses, 2nd Edition''. CRC Press, . In terms of standard measurements, the wing chord is , the
tail The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolution, evolved to los ...
is , the tarsus is and the
bill Bill(s) may refer to: Common meanings * Banknote, paper cash (especially in the United States) * Bill (law), a proposed law put before a legislature * Invoice, commercial document issued by a seller to a buyer * Bill, a bird or animal's beak Pl ...
is . Compared to the brown fish owl, the tawny averages of similar tail length, is larger in size by average wing length and bill size and slightly smaller in tarsal length.Weick, F. (2007). ''Owls (Strigiformes): annotated and illustrated checklist''. Springer.


Distribution and habitat

The tawny fish owl lives in
subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...
to
temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...
forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...
s in southern
Nepal Nepal, officially the Federal Democratic Republic of Nepal, is a landlocked country in South Asia. It is mainly situated in the Himalayas, but also includes parts of the Indo-Gangetic Plain. It borders the Tibet Autonomous Region of China Ch ...
,
northern India North India is a geographical region, loosely defined as a cultural region comprising the northern part of India (or historically, the Indian subcontinent) wherein Indo-Aryans (speaking Indo-Aryan languages) form the prominent majority populati ...
,
Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...
,
Bhutan Bhutan, officially the Kingdom of Bhutan, is a landlocked country in South Asia, in the Eastern Himalayas between China to the north and northwest and India to the south and southeast. With a population of over 727,145 and a territory of , ...
,
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
,
Laos Laos, officially the Lao People's Democratic Republic (LPDR), is the only landlocked country in Southeast Asia. It is bordered by Myanmar and China to the northwest, Vietnam to the east, Cambodia to the southeast, and Thailand to the west and ...
,
Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...
,
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...
, and
Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...
. It inhabits the Himalayan foothills from
Kashmir Kashmir ( or ) is the Northwestern Indian subcontinent, northernmost geographical region of the Indian subcontinent. Until the mid-19th century, the term ''Kashmir'' denoted only the Kashmir Valley between the Great Himalayas and the Pir P ...
and
Garhwal Garhwal may refer to the following topics associated with Uttarakhand, India: Places *Garhwal Himalaya, a sub-range of the Himalayas *Garhwal Kingdom, a former kingdom *Garhwal District (British Garhwal), a former district of British India * Ga ...
east to the mountains in Laos, Vietnam and southern China up to
Zhejiang ) , translit_lang1_type2 = , translit_lang1_info2 = ( Hangzhounese) ( Ningbonese) (Wenzhounese) , image_skyline = 玉甑峰全貌 - panoramio.jpg , image_caption = View of the Yandang Mountains , image_map = Zhejiang i ...
and
Anhui Anhui is an inland Provinces of China, province located in East China. Its provincial capital and largest city is Hefei. The province is located across the basins of the Yangtze and Huai rivers, bordering Jiangsu and Zhejiang to the east, Jiang ...
. It requires forest tracts with mountain streams. In areas such as
Darjeeling Darjeeling (, , ) is a city in the northernmost region of the States and union territories of India, Indian state of West Bengal. Located in the Eastern Himalayas, it has an average elevation of . To the west of Darjeeling lies the Koshi Pr ...
and Nepal, it lives at elevations of . Its range partly overlaps with the one of
brown fish owl The brown fish owl (''Ketupa zeylonensis'') is a fish owl species in the family known as typical owls, Strigidae. It is native from Turkey to South and Southeast Asia. Due its wide distribution it is listed as Least Concern on the IUCN Red List. ...
(''K. zeylonensis'') in Laos and Vietnam, where it prefers fast flowing waters in remote wilderness with little to no disturbance.


Behaviour and ecology

The tawny fish owl's territorial call is a deep ''whoo-hoo''. It also makes a cat-like ''meow''. Four tawny fish owls were equipped with
radio transmitters In electronics and telecommunications, a radio transmitter or just transmitter (often abbreviated as XMTR or TX in technical documents) is an electronic device which produces radio waves with an antenna with the purpose of signal transmission ...
in Taiwan and monitored from October 1994 to July 1996. They were mainly nocturnal, left their day-time roosts around sunset and returned before sunrise. They were most active moving and foraging during twilight, and moved up to in an hour. They moved more frequently in the cold season. In summer, breeding owls showed some daytime activity, consisting mainly of
preening Preening is a found in birds that involves the use of the beak to position feathers, interlock feather that have become separated, clean plumage, and keep ectoparasites in check. Feathers contribute significantly to a bird's insulation, waterp ...
. They also hunted during the day when feeding their fledglings. Each owl used up to 17 different
roosting Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight ...
sites that were all located in old-growth forest away from a stream. In the cold season, they roosted closer to streams, but also moved to uphill roosting sites in the warmer months. They avoided disturbed habitat like grassland, agricultural land and the vicinity of villages. The tawny fish owl is at least partially diurnal in activity, with daytime activity mainly occurring in the late afternoon and they may be seen actively hunting before nightfall especially on cloudy days. However, before the afternoon they tend to be sluggish during the day.Voous, K.H. 1988. ''Owls of the Northern Hemisphere''. The MIT Press, 0262220350. If disturbed or threatened, these owls tend to sit tight and not take flight. Like most owls, they usually choose inconspicuous perches during the day to avoid detection. The tawny fish owl has been described as the "most powerful and savage" of the three smaller fish owl species. The pellets of tawny fish owls in Taiwan were found on rocks, under perching and daytime roosts. They contained remains of Taiwan
mitten crab The Chinese mitten crab (''Eriocheir sinensis''; ; Jyutping: daai6 zaap6 haai5; Shanghainese: ''du6-zaq8-ha5'',  "big sluice crab"), also known as the Shanghai hairy crab (, p ''Shànghǎi máoxiè''), is a medium-sized burrowing cr ...
(''
Eriocheir ''Eriocheir'' is a genus of crabs, including the Chinese mitten crab, ''E. sinensis''. Formerly in the family Grapsidae, it is now placed in the Varunidae The Varunidae are a family (biology), family of thoracotrematan crabs. The delimitation ...
formosa''), tip-nosed frog ('' Odorrana swinhoana''), brown tree frog ('' Buergeria robusta''),
Asiatic toad The Asiatic toad or Chusan Island toad (''Bufo gargarizans'') is a species of toad endemic to East Asia. The species was previously classified as ''Bufo bufo gargarizans'', a subspecies of the common toad. Distribution and habitat It is commo ...
(''Bufo gargarizans''),
freshwater crab Around 1,300 species of freshwater crabs are distributed throughout the tropics and subtropics, divided among eight family (biology), families. They show direct development and maternal care of a small number of offspring, in contrast to marine c ...
s, shrimps and
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
. They took toads considerably more regularly than other frog species, although far less abundant in number in the stream and wetlands, due to their larger sizes. They usually hunt by swooping down to the water, capture fish from the surface and are reportedly surprisingly active in their hunting style and are not dissimilar in the hunting methods to those used by diurnal fish-hunting raptors such as fish eagles,
sea eagle A sea eagle or fish eagle (also called erne or ern, mostly in reference to the white-tailed eagle) is any of the birds of prey in the subfamily Haliaeetinae of the bird of prey family Accipitridae. Ten extant species exist, currently described w ...
s and
osprey The osprey (; ''Pandion haliaetus''), historically known as sea hawk, river hawk, and fish hawk, is a diurnal, fish-eating bird of prey with a cosmopolitan range. It is a large raptor, reaching more than in length and a wingspan of . It ...
s. More terrestrial prey is by no means avoided though and the species may also hunt
toad Toad (also known as a hoptoad) is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands. In popular culture (folk taxonomy ...
s,
lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...
s,
snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...
s, and small
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s such as
mole Mole (or Molé) may refer to: Animals * Mole (animal) or "true mole" * Golden mole, southern African mammals * Marsupial mole Marsupial moles, the Notoryctidae family, are two species of highly specialized marsupial mammals that are found i ...
s, and particularly
rodents Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...
, with one of the few mammalian prey recorded semi-regularly being
bamboo rat The bamboo rats are four species of rodents of the subfamily Rhizomyinae. They are the sole living representatives of the tribe Rhizomyini. These species are found in South Asia, Southeast Asia and East Asia. The species are: *The Chinese bamb ...
s (''
Rhizomys ''Rhizomys'', also known as bamboo rat, is a genus of rodents in the family Spalacidae The Spalacidae, or spalacids, are a family of rodents in the large and complex superfamily Muroidea. They are native to eastern Asia, the Horn of Africa, ...
''). A small
Malayan porcupine The Malayan porcupine or Himalayan porcupine (''Hystrix brachyura'') is a species of rodent in the family Hystricidae. Three subspecies are extant in South Asia, South and Southeast Asia. Geographical distribution The Malayan porcupine ranges f ...
(''Hystrix brachyura'') has also been reported amongst their prey. It also prey on birds including
Mandarin duck The mandarin duck (''Aix galericulata'') is a perching duck species native to the East Palearctic. It is Sexual dimorphism, sexually dimorphic – the males are elaborately coloured, while the females have more subdued colours. It is a medium- ...
s (''Aix galericulata'') in Taiwan and has overtaken large ground birds such
junglefowl Junglefowl are the only four living species of bird from the genus ''Gallus'' in the bird order Galliformes, and occur in parts of South and Southeast Asia. One of the species in this genus, the red junglefowl, is of historical importance as the ...
(''Gallus'' ssp.),
pheasant Pheasants ( ) are birds of several genera within the family Phasianidae in the order Galliformes. Although they can be found all over the world in introduced (and captive) populations, the pheasant genera's native range is restricted to Eura ...
s and eared pheasants, the latter sometimes weighing more than . Tawny fish owls tend to be sparsely distributed and frequently live in riparian zones of in length. Tawny fish owls are highly solitary and territorial as are a majority of owls. The breeding season is November to February in
India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
and December to February in
Assam Assam (, , ) is a state in Northeast India, northeastern India, south of the eastern Himalayas along the Brahmaputra Valley, Brahmaputra and Barak River valleys. Assam covers an area of . It is the second largest state in Northeast India, nor ...
. Nest locations found have included large holes in river banks, caves in cliffs and the fork or crotch of a large tree. As in all owls, tawny fish owls do not build a nest so merely lay their eggs on the bare ground of whatever surface they use. They also not infrequently nest in abandoned nests built by
Pallas's fish eagle Pallas's fish eagle (''Haliaeetus leucoryphus''), also known as Pallas's sea eagle or band-tailed fish eagle, is a large, brownish sea eagle. It breeds in the east Palearctic in Kazakhstan, Russia, Tajikistan, Turkmenistan, Uzbekistan, Mongolia, C ...
s (''Haliaeetus leucoryphus''). Usually two eggs are laid but sometimes only one is. The eggs can range in size from x , with an average of , and are similar in size to those of the brown fish owl. Greater details of the reproductive biology are not currently known although are presumed to basically be similar to those of other fish owls.


References

{{Taxonbar, from=Q1270506 tawny fish owl Birds of North India Birds of Eastern Himalaya Birds of China Birds of Yunnan Birds of Hong Kong Birds of Taiwan Birds of Laos Birds of Vietnam tawny fish owl Taxa named by Brian Houghton Hodgson Taxonomy articles created by Polbot