Yellow-bellied Prinia Prinia flaviventris 黃腹鷦鶯
Category I. Common resident in grassland, reed marsh and rank or herbaceous vegetation, and thus highest densities occur in the northwest New Territories.
Dec. 2010, CHUNG Wing Kin.
Very small with a long, graduated and loose tail, longest in the non-breeding season. In breeding plumage has grey head with narrow whitish supercilium in front of and above eye, olive brown upperparts, whitish throat, buffish chest and yellowish flanks, belly and undertail coverts. Eyes reddish brown and bill dark. In non-breeding plumage head and upperparts are paler, irides are pale brown and the bill blackish-brown with a pale base to the lower mandible. Legs are orange-flesh in both seasons. Juvenile is dull brown above with no grey head, has warm brown edges to remiges and a yellow was below; the eyes are pale.
Separated from Plain Prinia by greater contrast in plumage, usually brighter underparts, the narrow supercilium and the lack of pale lores.
The song is loud, rapidly delivered and high-pitched; it begins with a short slightly buzzing introduction followed by a melee of high-pitched notes, with a slight drop in pitch at the end. Usually a single strophe is uttered followed by a short gap, but occasionally two strophes are run together, as in this recording, at the end of which can be heard the snapping of the wings as it flies off, which is a characteristic sound of this species.
The alarm is a distinctive rising cat-like ‘eeuuhh’, rising and falling slightly though evenly across the call.
In addition, there is a ‘fee-tu’ uttered singly or in pairs; the function of this call is unknown but may also be one of alarm.
DISTRIBUTION & HABITAT PREFERENCE
Between the 1993-96 and 2016-19 breeding bird atlases there was a decrease in the percentage of occupied squares from 62.1% to 40.3%; a decline was also apparent in the winter atlas surveys of 2001-05 and 2016-19 from 45.1% to 38.2%. Breeding season declines have occurred on HK Island, Lantau and non-urban areas of the New Territories. The maturation of open-canopy shrubland to a closed-canopy habitat is no doubt an important driver of this decline, while the loss of urban or village fringe areas to development has presumably also been a factor in lowland areas (e.g. Lam Tsuen).
The stronghold of this species, where consistently high densities were recorded in the most recent breeding atlas, is the Deep Bay area from Tsim Bei Tsui to Hoo Hok Wai. It also occurs in relatively high densities in the north and northeast New Territories, the Kam Tin and Yuen Long areas, and scattered pockets of Sai Kung, Clearwater Bay, western New Territories and on Lantau, particularly in the southwest. Unlike Plain Prinia, it occurs on many offshore islands.
Yellow-bellied Prinia is found in nearly all types of grassland, including both hillside and wetland areas, as well as reed marsh and areas of rank or herbaceous vegetation such as those that develop on wasteland or fish pond bunds. Highest densities occur in open habitats, but it is also present in open-canopy shrubland and roadside vegetation in otherwise forested areas.
Trapping at Mai Po indicates that it is almost entirely sedentary, with evidence of only very limited movements: a ringed bird was seen 1km away and there were four records at the former airport at Kai Tak in March, April, September and November 1978.
Previous authors such as Swinhoe (1861), Kershaw (1904), Dove and Goodhart (1955) and Herklots (1967) reported it to be a common resident.
Song delivery increases once the cold midwinter weather has receded in late January or February. Breeding commences in late March and early April, with second clutches laid in June and July. Vaughan and Jones (1913) stated it was treble-brooded and that the nest is usually built of grass and bottle-shaped with an entrance near the top. Herklots (1967) noted a nest being built low down in a grassy hedge.
BEHAVIOUR, FORAGING & DIET
Prey includes insects and their larvae. Unobtrusive in grass or reeds when foraging.
Males are very territorial. The song is delivered throughout the year, though much less frequently in the final four months or on cold days in the winter. Vocal activity increases notably once temperatures rise in January or February. A characteristic species of grass or grassy-shrub habitats, its frequent and loud vocalisations can be heard unceasingly in the breeding season in some areas. Song is often delivered from the top of a grass stem or similar vantage point, and it makes an unusually (for its size) loud wing-snapping noise as it flies from perch to perch when agitated or excited, as in song.
RANGE & SYSTEMATICS
Occurs from eastern Pakistan and northwest India across northern India to the northeast of the country and south through southeast Asia and peninsular Malaysia to the Greater Sundas. In China it is common in coastal provinces of the southwest and southeast as far north as Shandong and occurs on both Hainan and Taiwan (Liu and Chen 2020).
P. f. sonitans occurs in southeast China, including HK, and northeast Vietnam. Six other subspecies are also recognised.
IUCN: Least Concern. Population trend decreasing.
Dove, R. S. and Goodhart, H. J. (1955). Field observations from the Colony of Hong Kong. Ibis 97: 311-340.
Herklots, G. A. C. (1967). Hong Kong Birds (2nd ed.). South China Morning Post, Hong Kong.
Kershaw. J. C. (1904). List of birds of the Quangtung Coast, China. Ibis 1904: 235-248.
Liu, Y. and Y. H. Chen (eds) (2020). The CNG Field Guide to the Birds of China (in Chinese). Hunan Science and Technology Publication House, Changsha.
Swinhoe, R. (1861). Notes on the ornithology of Hong Kong, Macao and Canton, made during the latter end of February, March, April and the beginning of May 1860. Ibis 1861: 23-57.
Vaughan, R. E. and Jones, K. H. (1913). The birds of Hong Kong, Macao and the West River or Si Kiang in South-East China, with special reference to their nidification and seasonal movements. Ibis 1913: 17-76, 163-201, 351-384.