Blue Rock Thrush Monticola solitarius 藍磯鶇
Category I. Locally common passage migrant and winter visitor with occasional summer records.
IDENTIFICATION
Apr. 2022, Derek Hon.
20-23 cm. Adult male M. s. philippensis has blue head, mantle, rump, thighs, chin, throat and upper breast; the wings and tail are darker; lower breast, belly and undertail coverts are chestnut-rufous.
Apr. 2021, D. A. Diskin. First-winter male pandoo.
Adult male M. s. pandoo has all-blue underparts. Some may show restricted chestnut barring on the lower belly and vent.
First-winter male pandoo is similar to the adult male but is scaled with variable pale and dark markings on the throat and breast and barred on the belly and undertail coverts.
Sep. 2016, Guy Miller.
Females of both races are variably grey brown with a blue-grey cast to the upperparts. The underparts are scaled brown and off-white on the breast and barred pale and dark on the belly and undertail coverts.
Dec. 2014, K. C. Kong.
First-winter male philippensis is duller than the adult male and scaled with variable pale and dark markings on the throat and breast and barred on the belly.
VOCALISATIONS
The call is a high-pitched inflected ‘sweet’ that falls sharply in pitch terminally. Also gives a ‘tschak’ call.
The song is a short fairly rich phrase not dissimilar to Blue Whistling Thrush Myophonus caeruleus in timbre due to the mixture of pure and trilling notes.
DISTRIBUTION & HABITAT PREFERENCE
Locally common passage migrant and winter visitor, mostly to rocky or coastal areas but sometimes village or farmland. Regular on village houses in the New Territories and occasional in urban areas. Frequently noted on rocky breakwaters and concrete dams. Favoured sites include southwest facing rocky coasts of Chek Lap Kok, Po Toi and Lamma Islands.
OCCURRENCE
Most records have occurred from mid-September to the end of April. There is a clear peak in reports between the last week of September and the third week of October, presumably involving both passage migrants and arriving winter visitors. Numbers remain relatively stable until the end of January (albeit with an anomalous peak in the last week of December) followed by a gradual decline from February to the end of March. Passage appears to occur in April, peaking in the last week of the month, but it is rare in May (Figure 1).
The highest single-site counts are 14 on Po Toi on 27 November 1996 and 27 September 2009; double-figure counts of this generally solitary species are rare, however.
There are occasional summer records that possibly indicate breeding activity locally, and since 1999 there have been reports in June and July in six years. The most interesting of these sightings involved two males chasing each other, with one in song, at Chek Lap Kok on 17 June 2011. However, breeding has not been confirmed.
Many reports are not assigned to subspecies. Of 169 individual males identified to race between 1999 and 2020, 103 (61%) were philippensis and 66 (39%) were pandoo. Previously pandoo was only “occasionally reported” (Carey et al. 2001), but the increase is probably due to a greater willingness to ascribe birds to taxon rather than a genuine increase.
Swinhoe (1861) noted it to be ‘numerous about the rocky hills’ during his visit in the first half of 1860; a similar situation was recorded by Kershaw (1904), Vaughan and Jones (1913) and Herklots (1936, 1953), though later authors commented on its preference for coastal areas, presumably as inland hills became more vegetated.
BEHAVIOUR, FORAGING & DIET
Usually, solitary and generally shy but readily perches out in the open on rocks, rooftops and overhead wires when undisturbed. Forages for insects by hopping and running on the ground or dropping down to the ground from a low vantage point. Three were seen hawking Red-base Jezebel Delias pasithoe butterflies over the sea at Chek Lap Kok on 7 January 2009. Also, one was seen eating unspecified fruit at Braemar Hill on 8 October 2011.
Herklots (1936) reported birds in song: two pandoo on unspecified dates and one philippensis in May. Recently males were heard in song at Chek Lap Kok on 30 April 2009 and 17 June 2011, and at Braemar Hill on 8 October 2011. None of these were identified to taxon.
RANGE & SYSTEMATICS
Blue Rock Thrush breeds from northwest Africa east through southern Europe and the Middle East to eastern Asia. Two subspecies, M. s. pandoo and M. s. philippensis, occur in east China, including HK.
M. s. pandoo breeds from the central Himalayas east to east China and North Vietnam. Wintering birds occur in south and southeast Asia south to the Greater Sundas. In China, it is largely resident south of the Yangtze as far west as southeastern Tibet. M. s. philippensis breeds in east Mongolia, northeast China south to Shandong, Korea, Sakhalin, South Kuril Islands, Japan, Ryukyu Islands, coastal Taiwan and north Philippines (Batanes Island); it winters in coastal provinces of southeast China, southeast Asia and the Philippines south to the Sundas, the Moluccas and Palau. A third taxon, M. s. longirostris, is a migrant through southwestern Tibet (Cheng 1987, Collar 2020, Yang and Chen 2020).
CONSERVATION STATUS
IUCN: Least Concern. Population trend stable.
Figure 1.
Cheng, T. H. (1987). A Synopsis of the Avifauna of China. Science Press, Beijing.
Collar, N. (2020). Blue Rock-Thrush (Monticola solitarius), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.burthr.01
Herklots, G. A. C. (1936). The birds of Hong Kong. Part XXIV. Family Turdidae (Thrushes). Hong Kong Naturalist 7: 137-147.
Herklots, G. A. C. (1953). Hong Kong Birds. South China Morning Post, Hong Kong.
Kershaw. J. C. (1904). List of birds of the Quangtung Coast, China. Ibis 1904: 235-248.
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 K. H. Jones (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.
Liu, Y. and Y. H. Chen (2020). The CNG Field Guide to the Birds of China (in Chinese). Hunan Science and Technology Publication House.
