Red Knot Calidris canutus 紅腹濱鷸
Category I. Common passage migrant in spring, scarce in autumn and rare in winter. Numbers in spring and autumn lower than in the 1990s.
IDENTIFICATION
Apr. 2021, John and Jemi Holmes.
Short legged, slightly stockier than Great Knot, compared to which it has a shorter bill that approximately equals its head length and more greyish rump and uppertail coverts. In breeding plumage has orange underparts that are richer on the male and dark grey legs.
C. c. piersmai has brick-red underparts, reddish nape and upperparts heavily marked with black and rufous. C. c. rogersi has paler underparts often marked with black and a pale grey nape (Baker et al. 2020). This bird is probably rogersi due to its largely whitish vent and undertail coverts and lack of obvious reddish nape.
Nov. 2021, Sarawak, Malaysia, Dave Bakewell.
Non-breeding birds are rather plain grey with greenish legs; this bird is moulting to first-winter plumage and still has juvenile wing coverts, which have obvious narrow dark subterminal fringes and shaft streaks and pale fringes. Juveniles also have a buff wash to less streaked chest.
May 2014, Michelle and Peter Wong.
This first-summer bird, indicated by the worn and faded tertials and rearmost scapulars, shows only traces of breeding plumage.
VOCALISATIONS
A short ‘kyow’ may be uttered when foraging.
DISTRIBUTION & HABITAT PREFERENCE
Most records are from the intertidal mudflats of Deep Bay and adjacent roosting areas of Mai Po NR. There are few records of grounded birds away from there: singles at the former airport of Kai Tak on 29 May 1975 and 28 April 1978, a juvenile at Shuen Wan on 24 September 1994, two on a fish pond at San Tin on 20 April 2011, one at Tai Sang Wai on 19 April 2013 and two at Shui Hau, Lantau on 2 May 2020. In addition, up to 31 have been seen in flight over the sea in spring.
OCCURRENCE
Red Knot is primarily a spring passage migrant through Hong Kong with lower numbers on autumn passage (Figure 1) and no more than a few birds in winter.
Relatively few passage birds appear before the last week of March, and spring arrivals are usually obvious in early April. This century there have been no counts higher than 20 until the final week of the month, while in the 1990s higher counts were apparent from the middle of the month. Peak spring passage occurs in the first half of May, and most birds have passed through by the end of the month. In the 1990s the highest spring counts were 200 on 6 May 1990 and 190 on 5 May 1991; this compares with peak counts this century of 148 on 1 May 2020 and 123 on 4 May 2018. Figure 2 indicates that, on average, systematic shorebird counts in the ten years from 1998 recorded higher peak counts than in the ten years to 2020.
The latest spring record is of five on 10 June 1989. Very few individuals of this high Arctic breeding species are recorded in summer, and there are only three such records: two on 28 June 1980, one from 28 June to 18 July 2011 and one on 31 July 2020.
Autumn passage is generally noted from the last week of August, with the earliest record in the month being two adults on 7 August 1993. The main period of the protracted but weak autumn passage extends to the final week of October with a small peak in the third week of September. The highest autumn count this century is 14 on 20 September 2020, which contrasts with the situation in the 1990s when, apart from peak weekly counts of 62-93 birds recorded between 30 September and 19 November 1991 (the highest on 7 October), autumn records were of up to 35 birds.
Apart from up to 24 birds seen in mid-November 2013 and a count of 14 on 5 February 2010, all records this century in the November to February period have been of eight birds or fewer. This is broadly like the situation in the 1990s apart from the early years when unusually high numbers were present, including a peak count of 80 on 9 November 1991, at least 64 of which remained on 24 January 1992.
C. c. piersmai has been reported from 3 April to 4 June, and C. c. rogersi from 5 April to 4 May; the former is generally more numerous. In autumn juveniles have been recorded from 24 August to 22 October and adults on 7 August and from 7 September to 25 October. Red Knots bearing yellow northwest Australian leg-flags have been noted in spring, while two trapped and ringed at Mai Po were controlled at Broome, northwest Australia.
Red Knot was first recorded in Hong Kong on 18 May 1957 by Walker (1958).
BEHAVIOUR, FORAGING & DIET
Unobtrusive when in non-breeding plumage or in low numbers on the mudflat.
RANGE & SYSTEMATICS
An Arctic breeding species in north and northeast Canada, north Greenland, north central Siberia, the New Siberian Archipelago, northeast Siberia and west Alaska. Winters coastally in southern latitudes of the northern hemisphere and much of the southern hemisphere (Baker et al. 2020). In China mainly a migrant through coastal areas of the east and south, with very small numbers passing inland; small numbers winter along the south coast including Hainan and Taiwan (Liu and Chen 2020).
Six subspecies are recognised, of which four could theoretically occur in HK. Of the four, the two that have been identified in the field and the most likely are C. c. piersmai and C. c. rogersi, both of which winter in Australasia, the former breeding in the New Siberian Archipelago and the latter on the Chukotka Peninsula. Least likely of the four to occur are nominate canutus, which breeds in north central Siberia and winters in Africa, and C. c. roselaari, which breeds on Wrangel Island, northeast Siberia, and winters in the eastern Pacific. The remaining two subspecies breed in north Canada and north Greenland.
CONSERVATION STATUS
IUCN: NEAR-THREATENED. Numbers decreasing in some subpopulations, including those using the East Asian-Australasian Flyway as a result of habitat loss in the Yellow Sea.
Figure 1.
Figure 2.
Baker, A., P. Gonzalez, R. I. G. Morrison, and B. A. Harrington (2020). Red Knot (Calidris canutus), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.redkno.01
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.
Walker, F. J. (1958). Field observations on birds in the Colony of Hong Kong. Hong Kong Bird Watching Society, Hong Kong (duplicated).
