|Tawny fish owl|
|Cultrunguis flavipes Hodgson, 1836|
The tawny fish owl (Ketupa flavipes) is a fish owl species in the family known as typical owls, Strigidae. It is native from southern Nepal to Bangladesh, Vietnam and China. Due its wide distribution it is listed as Least Concern on the IUCN Red List.
Cultrunguis flavipes was the scientific name proposed by Brian Houghton Hodgson in 1836 who described a yellow-footed fish owl from Nepal.
Ketupa was proposed as generic name by René-Primevère Lesson in 1831 for fish owl species from Java and India.
Results of a phylogenetic analysis of nine horned owl species indicate that Ketupa species form a monophyletic group.
The tawny fish owl has large ear tufts usually hanging to the sides of the head and looking tousled. Its eyes are yellow. Its crown and upperparts are orange-rufous overlaid with broad, blackish markings on the central part of the feathers. It is dull yellow across the shoulders, whereas flight and tail feathers are dark brown and buff. Its facial disc is pale and off-white streaks on eyebrows and forehead. Its kegs are partly feathered with bare toes and greenish-yellow claws. It is 48 to 58 cm (19 to 23 in) long from bill to tail. Its wing chord is 410 to 477 mm (16.1 to 18.8 in), the tarsus 60 to 67 mm (2.4 to 2.6 in) with a tail of 215 to 227 mm (8.5 to 8.9 in), and the bill 48 to 52 mm (1.9 to 2.0 in). Adult tawny fish owls weigh between 1,050 and 2,650 g (2.31 and 5.84 lb).
The feathers of fish owls are not soft and lack the comb and hair-like fringes to the primaries, which allow other owls to fly silently. Due to the lack of these specializations, fish owl wing beats make sounds. The fish owls’ lack of a deep facial disc is another indication that sound is less important than vision, as facial disc depth and inner ear size are directly related to how important sound is to an owl’s hunting behavior.
Distribution and habitat
The tawny fish owl lives in subtropical to temperate forests in southern Nepal, northern India, Bangladesh, Bhutan, China, Laos, Myanmar, Taiwan, and Vietnam. It inhabits the Himalayan foothills from Kashmir and Garhwal east to the mountains in Laos, Vietnam and southern China up to Chekiang and Anhwei. It requires forest tracts with mountain streams. In areas such as Darjeeling and Nepal, it lives at elevations of 1,500 to 2,450 m (4,920 to 8,040 ft). Its range partly overlaps with the one of brown fish owl (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 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 1,800 m (5,900 ft) in an hour. They moved more frequently in the cold season. In summer, breeding owls showed some daytime activity, consisting mainly of preening. They also hunted during the day when feeding their fledglings.
Each owl used up to 17 different roosting sites that were all located in old-growth forest 20 to 550 m (66 to 1,804 ft) 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 pellets of tawny fish owls in Taiwan were found on rocks, under perching and daytime roosts. They contained remains of Taiwan mitten crab (Eriocheir formosa), tip-nosed frog (Odorrana swinhoana), brown tree frog (Buergeria robusta), Asiatic toad (Bufo gargarizans), freshwater crabs, shrimps and fish. 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 eagles and ospreys. More terrestrial prey is by no means avoided though and the species may also hunt toads, lizards, snakes, and small mammals such as moles, and particularly rodents, with one of the few mammalian prey recorded semi-regularly being bamboo rats (Rhizomys). A small Malayan porcupine (Hystrix brachyura) has also been reported amongst their prey. It also prey on birds including Mandarin ducks (Aix galericulata) in Taiwan and has overtaken large ground birds such junglefowl (Gallus ssp.), pheasants and eared pheasants, the latter sometimes weighing more than 2 kg (4.4 lb). Tawny fish owls tend to be sparsely distributed and frequently live in riparian zones of 5.5–7.7 km (3.4–4.8 mi) 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 and December to February in Assam. 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 eagles (Haliaeetus leucoryphus). Usually two eggs are laid but sometimes only one is. The eggs can range in size from 56 to 58.8 mm (2.20 to 2.31 in) x 45.5 to 48.3 mm (1.79 to 1.90 in), with an average of 57.1 mm × 46.9 mm (2.25 in × 1.85 in), 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.