IDENTIFICATION

VOCALISATIONS

Pairs engage in a duet consisting of three pairs of notes, the first and third pair uttered by the male, the second by the female. When vocalising in this way, the throat is distended emphasising the contrast provided by the white feathers. Low in pitch, the sound is clearly audible only in favourable conditions. Sometimes the male will call but the female may not be present or may not respond.

Adults may give a loud inflected screech.

The juvenile begging call at the nest is an inflected rather wheezy ‘zhweet’ (heard in this recording with calls of begging juvenile and adult Collared Scops Owl in the background).

The female has been recorded uttering a harsh screeching call during distraction display.

The following calls were uttered by a female when the juvenile was approached too closely.

DISTRIBUTION & HABITAT PREFERENCE

Widely but thinly distributed in the New Territories and on Lantau and Cheung Chau, typically below 150m asl, with occasional records from HK Island. Occurs in well-wooded areas near water, including freshwater streams and marshes, reservoirs, catchwaters, tidal creeks and even a harbour; it occasionally strays into more anthropogenic habitats such as a public garden or golf course. Favoured sites include the Tai Lam CP reservoirs, Pak Sha O and Cheung Chau harbour.

OCCURRENCE

Records occur throughout the year and typically involve a single bird or pair detected usually detected visually. Though only accounting for a minor proportion of records, vocalising birds have been noted in all months except November. Approximately 248 birds were recorded at 40 sites in the years 1999-2021 (excluding young birds at or near the nest). The pattern of detections through the year is not even, with the months March-May, when adults are often conspicuous and vocal near nest-sites, accounting for almost half the total and troughs apparent in June-July and December.

A spectacular increase has occurred since 2000. In the first nightbird survey of 2000-2001 none were recorded despite good coverage of known sites (Lewthwaite & Yu 2007); in contrast, 51 birds were recorded at 15 sites in the second survey of 2020-2021 (Lewthwaite & Fong in prep.). The number of individuals recorded steadily increased in successive three-year periods between 2004-2006 and 2016-2018 and then more than tripled in 2019-2021. Similarly, the number of sites with records increased steadily from 2004-2006 to 2016-2018 before almost doubling in 2019-2021.

Greater observer coverage has contributed to higher detection rates, but the major factor behind the increase is thought to be the spread of shrubland and its maturation into secondary forest, especially in the vicinity of reservoirs and streams.

The first records were single specimens from HK Island collected in or before 1855 (Cassin 1862) and in 1860 (Swinhoe 1861), the latter probably in the Caroline Hill area. Swinhoe also described finding a roost-site above Happy Valley Cemetery, probably near Stubbs Road. Subsequent reports in the 1930s and 1950s were also from HK Island, with a juvenile on a ledge near Pok Fu Lam Reservoir on 27 April 1931 (Hutson 1931), a site where the species bred regularly according to Herklots (1939), and one captured at Mount Parker in late March 1955 (Macfarlane and Macdonald 1960). Subsequently, the only substantiated records before 1999 involved two adults and a dependent juvenile near Discovery Bay in 1988 and one or two birds at Tai Tan, Yung Shue O and Pak Tam in 1992-1999, which led to the species being regarded as a scarce resident at this time (Carey et al. 2001).

BREEDING

Seven nest-sites with one or two young birds present have been found, all in or near well-wooded areas in the years 2009-2021: four on roof-tops or balconies, one on a concrete ledge above a channel draining into a reservoir, one (used in at least three years) on a ledge among buttress roots of a large tree at the top of a concrete slope, and one in a natural tree hollow. As these suggest, Brown Fish Owl is fairly tolerant of diurnal disturbance from adjacent buildings.

Though the earliest hatching date may possibly be the second half of February, nest-site observations provide the following timetable in the development of young birds: downy white chicks (18 March to 11 April), unfledged juveniles (8-29 April), first flight of juveniles (28 March to 28 April), and post-fledging nest dependency (28 March-11 June). Nest-site observations also show that for at least two months after the young hatch, adults spend long periods on guard in the nest-site vicinity and may give distraction displays if the nest area is approached. Sightings of a juvenile accompanied by one or two adults at a feeding site at Discovery Bay on 5^th and 11 August 1988 suggest that juveniles may remain dependent on adults for several months after fledging.

BEHAVIOUR, FORAGING & DIET

Nocturnal and secretive but may occasionally be seen at or near a nest-site in the day-time (especially after heavy rain) or emerging from a woodland roost-site just before dusk; individuals have been recorded sitting for long periods on a boat near a busy harbour-front or on the roof of a nearby building. Forages at lowland streams, freshwater marshes (when it has been seen using adjacent lamp posts as a look-out), reservoirs, tidal creeks, a harbour and also the forest floor. Food items recorded in HK are crabs and small marine animals (Swinhoe 1861), fish and rodents (Leong 2021), and snakes and amphibians, including Asian Common Toad Duttaphrynus melanostictus.

Griffiths and Ades (2008) reported on the movements of a rehabilitated adult that was released in Sai Kung Peninsula in November 2003 and radio-tracked for 3 months until the transmitter fell off. The tracking data indicated that it frequently moved from site to site and roosted in patches of woodland near small rural villages, within a short flying distance of streams, a reservoir or the sea. A bird at Pak Sha O was disturbed from a diurnal roost site on a branch no more than 1m above a stream.

Duetting occurs mainly March to May, though can be as early as February. It mainly occurs from 15-30 minutes after sunset, though may extend to one hour after. Following this, birds often fly off to forage.

Appears able to tolerate a moderate level of disturbance near the nest site in the daytime, though substantially less in the evening.

RANGE & SYSTEMATICS

Distributed from Turkey and the Middle East through India and parts of Burma and Indochina south to northern Malaysia and east to southeast China (Holt et al. 1999, Konig et al. 2008). Polytypic, with four subspecies recognised, including orientalis on Hainan and from southeast Yunnan to Guangdong and southern Jiangxi.

CONSERVATION STATUS

IUCN: Least Concern. Population trend decreasing.