Common Greenshank Tringa nebularia 青腳鷸
Category I. Abundant passage migrant and common winter visitor to Deep Bay area, with scattered records elsewhere.
IDENTIFICATION
Apr. 2018, Michelle and Peter Wong. Adult.
30-35 cm Elegant wader with slightly upturned fairly broad-based bill and longish green or grey-green legs. Generally greyish with white underparts. This adult is acquiring the dark centred scapulars and streaked head and chest of breeding plumage.
Adult winter is paler and greyer with more extensive white on underparts. Juvenile darker above with neat pale fringes to upperparts and fine streaking on chest and upper flanks.
Jan. 2023, Sarawak, Malaysia. Dave Bakewell.
In flight white tapers from the uppertail coverts to a point on the mantle at approximately the leading edge of the wing; the tail feathers are lightly barred (usually darker on the central feathers), the wings are plain and the legs project beyond tail. See Nordmann’s Greenshank and Marsh Sandpiper for comparison.
VOCALISATIONS
The typical flight call is a ringing and distinctive ‘tyoo’ uttered 2-5 times; it may be repeated more frequently or more hoarsely by more excited birds. These variations can be heard in the recordings selected.
DISTRIBUTION & HABITAT PREFERENCE
Most records are from the intertidal mudflats of Deep Bay and adjacent roosting areas, primarily Mai Po NR. Also regularly recorded at Long Valley where the highest count is of eight birds. Up to 17 have been recorded in freshwater habitats in the Kam Tin area, but no more than three in the channelised watercourse. Surprisingly rare on Lantau given the availability of intertidal mudflat, with single birds recorded on only a small number of occasions this century.
Elsewhere, the species has been noted at scattered coastal localities throughout the New Territories, generally singly or in groups of up to eight birds, apart from records of 40 migrating over the sea south of HK Island on 24 April 1994 and 26 at Luk Keng on 1 May 2009.
OCCURRENCE
Common Greenshank is an abundant passage migrant, common winter visitor and scarce summer visitor. In what is an extended autumn passage, apparent migrants are first noted during the first half of July; subsequently numbers increase to a peak around the third week of September followed by a decline, with the wintering population probably established by mid-November (Figure 1). The highest autumn count is 1,816 on 22 August 2006. Figure 2 illustrates peak spring and autumn counts since 1992 and shows that autumn counts of Common Greenshank increased to a peak in 2006 before falling to a low in 2019.
As Figure 3 indicates, the peak count of wintering birds generally numbered no more than 400 until winter 2002/03; subsequently there was an increase to whole Deep Bay peaks of over 1,500 from winter 2006/07 to 2008/09 (highest 1,717 on 21 December 2008), with the highest count on the HK side of the bay being 1,489 on 13 January 2008. Since then, peak counts have been substantially lower, mostly up to 800. This pattern broadly matches that observed in peak counts in both spring and autumn. Based on winter waterbird counts in Deep Bay Sung et al. (2021) concluded that the wintering population increased from 1998 to 2017.
Spring migrants are probably present in the first week of March. The main period of passage is rather prolonged, lasting from the last week of March to the second week of May and peaking in the first week of the latter month (Figure 1). The highest count is 1,918 on 19 April 2008. A sharp drop in numbers occurs at the end of the first week of May. Up to 136 birds have been recorded in June and early July in Deep Bay. Figure 2 indicates that peak spring counts of Common Greenshank increased to a peak in 2008 before falling to a low in 2017 and 2018, broadly matching the pattern of autumn and winter counts. One bird ringed at Mai Po was shot in central Siberia.
Vaughan and Jones (1913) referred to Common Greenshank as a ‘common winter visitor’ arriving on 21st or 22 September and leaving between 3 March and 1 April. Dove and Goodhart (1955) noted passage birds from 18 April to 16 May and 30 August to 9 October, though it was neither regular nor numerous. Herklots (1957) noted there were then records for every month of the year.
BEHAVIOUR, FORAGING & DIET
Pecks and probes in shallow water at a consistent pace but may also run quickly with sudden sharp changes of direction when opportunistically exploiting prey abundance. Has been observed predating mudskippers greater than its bill length. Has been recorded on nocturnal migration over Sai Kung.
RANGE & SYSTEMATICS
Monotypic. Breeds between approximately 50oN and 70oN from Scandinavia east through Russia and northern Kazakhstan to Kamchatka; winters in coastal north and sub-Saharan Africa, the Middle East, the Indian subcontinent and south China south through Indochina, southeast Asia and Indonesia to Australia (Van Gils et al. 2020). In China a migrant through much of the country and winter visitor from the Yangtze floodplain south to the coast, including Hainan and Taiwan (Liu and Chen 2020).
CONSERVATION STATUS
IUCN: Least Concern. Population trend stable.
Figure 1.
Figure 2.
Figure 3.
Dove, R. S. and H. J. Goodhart (1955). Field observations from the Colony of Hong Kong. Ibis 97: 311-340.
Herklots, G. A. C. (1953). Hong Kong Birds. South China Morning Post, Hong Kong.
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.
Sung, Y. H., C. C. Pang, T. C. H. Li, P. P. Y. Wong and Y. T. Yu (2021). Ecological Correlates of 20-Year Population Trends of Wintering Waterbirds in Deep Bay, South China. Frontiers in Ecology and Evolution. Published 20 April 2021 doi: 10.3389/fevo.2021.658084
Van Gils, J., P. Wiersma, and G. M. Kirwan (2020). Common Greenshank (Tringa nebularia), 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.comgre.01
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.
