IDENTIFICATION

VOCALISATIONS

The territorial call, which consists of 2-7 slightly drawn-out notes that are fairly rapidly repeated, can be heard from October to May in the breeding season.

In general, the varied vocalisations of this species are deeper than either Collared Crow or Carrion Crow.

DISTRIBUTION & HABITAT PREFERENCE

Occurs throughout HK in a wide variety of habitats, though it uses forest and closed-canopy shrubland for nesting and roosting rather than foraging. Densities are lower in heavily urbanised areas of Kowloon and the more urbanised areas of the lowland New Territories.

Between the breeding bird surveys of 1993-96 and 2016-19 there was an increase in the percentage of squares in which the species was recorded from 29.7% to 38.8%. Similarly, there was an increase in the winter atlas surveys of 2001-05 and 2016-19 from 32.4% to 42.1%. There were increases in the northwest New Territories and on HK, Lantau and Lamma Islands in both seasons. In the winter there were increases in northeast New Territories and northern and southern areas of the Tai Mo Shan massif, while in the breeding season there were increases in the northern New Territories.

OCCURRENCE

Swinhoe (1861) specifically noted he did not record Large-billed Crow at Guangzhou, though he knew it from Fujian; nor was it recorded by Kershaw (1904) or Vaughan and Jones (1913). However, the latter authors did have winter records of Rook at Ding Hu Shan, and it is possible that the two species were confused. It was subsequently listed for Guangdong by La Touche (1925-30), though no specific localities were mentioned.

The first documented record for Hong Kong was on 24 March 1934, when two birds were seen at Sha Tau Kok (Pereira and Herklots 1934); during the following two years there were records of a further seven birds at Sai Kung, Kam Tin and Lam Tsuen valley (Herklots 1935). With respect to these, Herklots stated that he had looked out for the species for several years without success, so it is surmised that Large-billed Crow was genuinely a new arrival at this time.

Herklots (1953) stated that single birds or pairs were occasional in Lam Tsuen valley, Tai Po and Sha Tau Kok areas, but that there were no records from HK Island. However, Dove and Goodhart (1955) referring to the years 1952-53, recorded it from Pok Fu Lam on HK Island, as well as on Stonecutters and several localities in the New Territories. The early 1950s appear to have been a period of rapid expansion: as well as Dove and Goodhart’s observations, unpublished records subsequently collated by HKBWS refer to a single bird at Shouson Hill on 24 May 1953 and one bird there and two at Pok Fu Lam in 1954. In 1955 a flock of 12 birds was seen on Mount Davis and by 1958 small numbers of birds were recorded all over HK Island. Numbers were also increasing at this time in the New Territories, especially around Tolo Harbour and, by 1961, up to 15 were regularly seen in the Sha Tin area.

Increasing numbers can be illustrated with reference to successive increases in the largest flock sizes reported: 30 at Tai Tam on 11 December 1963, 40 at Mai Po on 23 May 1965, 78 at Tai Po on 21 April 1976, 125 at Lam Tsuen on 23 October 1982, 150 at Tai Lam CP on 31 January 1995, 200 there on 20 January 2008 and 266 at Tuen Mun Leung Tin Au Trail on 7 October 2020. The northwest New Territories area now is the area where high counts are regularly made. Some range increases were still taking place during the early 1980s, particularly in the Deep Bay area; in addition, Viney (1996) recorded a marked increase in numbers at Mount Nicholson at this time.

Large-billed Crow has traditionally been regarded as a resident species for which there is no evidence of migration or substantive movements. However, observations by Welch (2014) indicate that at least local movements do occur. During March and early April 2006-12 small flocks were seen flying across the island from west to east or heading out towards the Dangan Islands. The highest day count of such birds was 16. On two occasions a pair from one of these flocks apparently remained to breed, away from the resident pair, indicating the manner by which the species may have colonised HK. Welch (2014) postulates that post-breeding dispersal of juveniles may result in birds grouping together for the non-breeding season prior to further dispersal in spring, as birds seek their own territories.

BREEDING

There are relatively few confirmed breeding records, possibly due to the fact that nest sites are not conspicuous. There appears to be a substantial population of non-breeding birds away from forest areas, which is typical of corvid population structure (Cramp and Perrins 1980).

An increase in pair activity is noted in October, while display has been noted on 9 November. The territorial call of the male is generally heard from October into early spring. Collection of nest materials has been observed mid-March, while carrying of food to the nest was seen on 27 April and an occupied nest has been noted as late as 9 June.

BEHAVIOUR, FORAGING & DIET

Largely a scavenger, it has been noted feeding on the remains of Eurasian Teal. In addition, it has been recorded taking an egg and carrying a chick taken from a nest. However, these are the only observations of food consumption despite it being a large and obvious species.

Although typically seen as singles or pairs, Large-billed Crows can gather in large groups at roosts or near productive food sources. The largest numbers are typically observed either feeding at landfill sites or at pre-roost gatherings: the latter are often on electricity pylons or high-tension cables.

Interestingly, one was observed collecting hair from a buffalo at Pui O, Lantau on 18 March 2020.

RANGE & SYSTEMATICS

Occurs from northern Afghanistan and Pakistan through most of India and the Himalayas east and north to China, Korea, Japan, Kamchatka and southern Ussuriland, and south through Indochina to Sumatra, Java, parts of the Lesser Sundas and the Philippines (Madge 2020). In China it is resident in much of the country, with the exception of the dry plateau or desert areas of the northwest and north (Liu and Chen 2020).

C. m colonorum occurs in central and south China including HK, as well as Hainan and Taiwan. Eight other subspecies are recognised, two of which occur in China.

CONSERVATION STATUS

IUCN: Least Concern. Population trend stable.