Justification of Red List category
This species has been uplisted to Endangered owing to recent evidence showing a very rapid population decline caused by reclamation of non-breeding stopover grounds, and under the assumption that further proposed reclamation projects will cause additional declines in the future.
The global population was estimated to number c. 380,000 individuals in 2006 (Wetlands International 2006). However following the reclamation of the tidal flats at Saemanguem (South Korea), c. 90,000 non-breeding individuals disappeared from the area. Surveys elsewhere in South Korea confirmed they had not been displaced, and a decline of the same magnitude and timing in Australia suggests that individuals previously using Saemanguem have died (D. Rogers in litt. 2009). Therefore a new global population was estimated at 292,000-295,000 individuals in 2007 (Wetlands International 2015).
An analysis of monitoring data from Australia and New Zealand suggests the population is declining at a much more rapid rate than was previously thought, with an estimated 77.8% decline over three generations (22 years) (Studds et al. in prep.). Almost the entire global population (98%) is restricted to the East Asian-Australasian Flyway so trends in the Australasian population during the non-breeding season are thought to be representative of the overall global population.
New data looking at adult survival supports these estimated rapid declines (Piersma et al. submitted). The study found that whilst survival in north-west Australia in winter remained constantly high, the survival rate during time away from Australia, declined from 2011. During 2011-2012 the annual survival rate for the species was 0.63 and annual breeding output was 0.15. Given such low survival rates the study estimates the species will halve in number within four years. If these rates are representative of the whole population then the declines stated here could be even more severe. Reclamation of Saemangeum (South Korea) alone has caused a decline of c. 90,000 individuals, equating to a population decline of approximately 25% since 2000 (N. Moores in litt. 2009, D. Rogers in litt. 2009). Furthermore there have been documented declines in some of the peripheral sites for the species in Australia and Japan (Amano 2006, R. Clemens in litt. 2010). Given that many more reclamation projects are proposed within the Yellow Sea region, it is reasonable to assume that declines will continue in the future.
This species breeds in north-east Siberia, Russia, wintering mainly in Australia, but also throughout the coastline of South-East Asia and on the coasts of India, Bangladesh, Pakistan, and the eastern coast of the Arabian Peninsula (del Hoyo et al. 1996). The Yellow Sea of North Korea, South Korea and China is a particularly important stop-over site on migration in both spring and autumn. The Yalu Jiang coastal wetland in the north Yellow Sea has been identified as a key site for the species during northward migration (Choi et al. 2014). It is thought that the southern Yellow Sea is used as a temporary stopover area whilst the northern Yellow Sea acts as a key staging site where birds refuel (Ma et al. 2013). The global population has been estimated at 380,000 individuals, of which 176,000 were thought to pass through South Korea (Wetlands International 2006). Since then the reclamation and development of wetlands in South Korea has led to a decline in the observed counts of non-breeding populations, mostly notably including dramatic declines at the Saemangeum wetland which previously held c.20-30% of the global population on migration (Moores in litt. 2009, Rogers et al. in litt. 2009). The population estimate has therefore been updated accordingly with the most recent population size thought to be 292,000-295,000 individuals in 2007 (Wetlands International 2015).
Despite there being no observed declines within the Chinese portion of the Yellow Sea, further declines at smaller staging grounds in Japan and at major wintering grounds in Australia (of c.90,000 individuals [Rogers et al. 2009]) make it clear that the population is declining overall (Amano 2006, Moores et al. 2008, R. Clemens in litt. 2010). These are supported by recent data from Australasia suggesting that the population has decreased by 77.8% over three generations (22 years) (Studds et al. in prep.).
The species breeds on gravelly areas covered with lichen and patches of herbs, heather (del Hoyo et al. 1996), Empetrum spp., Dryas spp. and Vaccinium spp.(Johnsgard 1981), or alternatively on areas with a continuous layer of lichen and scattered stunted larch Larix spp. or dwarf pine Pinus pumila (del Hoyo et al. 1996). It occurs on plateaus or gentle slopes with montane tundra in the subarctic at heights of 300-1,600 m (del Hoyo et al. 1996). In its wintering range the species occurs in sheltered coastal habitats such as inlets, bays, harbours, estuaries and lagoons with large intertidal mud and sandflats, oceanic sandy beaches with nearby mudflats (del Hoyo et al. 1996, Higgins and Davies 1996), sandy spits and islets, muddy shorelines with mangroves and occasionally exposed reefs or rock platforms (Higgins and Davies 1996). It roosts in refuges (Rogers et al. 2006) such as shallow water in sheltered sites, on coastal dunes or on saltflats amongst mangroves (Higgins and Davies 1996) during high tides (Rogers et al. 2006).
On passage the species stages in estuaries and on intertidal mudflats (Tomkovich 1997, Moores 2006). The adult breeding diet consists predominantly of plant material such as berries (del Hoyo et al. 1996) (e.g. of Empetrum nigrum) (Johnsgard 1981) and pine kernels of dwarf pine Pinus pumilla (del Hoyo et al. 1996). Small chicks feed exclusively on insects (e.g. larval Diptera and Coleoptera) and spiders (del Hoyo et al. 1996). During the winter and on passage the species takes bivalves up to 36 mm long from intertidal mudflats as well as gastropods, crustaceans (del Hoyo et al. 1996) (e.g. crabs and shrimps) (Higgins and Davies 1996), annelid worms and echinoderms (e.g. sea cucumbers) (del Hoyo et al. 1996). The nest may be an open depression in moss (Flint et al. 1984) but very few nests have been found (Johnsgard 1981). This species is a long-distance migrant that largely travels along the coast making few stopovers (del Hoyo et al. 1996) but utilising different routes in the autumn and the spring (del Hoyo et al. 1996, Higgins and Davies 1996). It breeds from late-May to late-June, departing the breeding grounds in July and arriving on the wintering grounds between August and October (del Hoyo et al. 1996). The return migration to the breeding grounds takes place from March to April (del Hoyo et al.1996) although juvenile non-breeders often remain in the tropical parts of the wintering range for the breeding season (Hayman et al. 1986). The species forages in large flocks of one hundred to several thousand (del Hoyo et al.1996) at favoured sites on passage (Hayman et al. 1986), but during the winter it typically forages in small groups (Johnsgard 1981).
Loss of intertidal stopover habitats in the Yellow Sea region is thought to be a key driver in population declines of shorebirds (Amano et al. 2010, Yang et al. 2011). Up to 65% of intertidal habitat in the Yellow Sea has been lost over the past 50 years with habitat loss estimated at a rate of >1% annually (Murray et al. 2014). Losses are attributed to reclamation for agriculture, aquaculture, and other development and are expected to continue or accelerate owing to population growth around the Yellow Sea. Degradation and loss of wetland habitats in the Yellow Sea region are also attributed to environmental pollution (Kelin and Qiang 2006) (e.g. oil contamination of intertidal mudflats) (Tomkovich 1997), reduced river flows and human disturbance (Kelin and Qiang 2006) (e.g. from off-road vehicles, tourists and hunters) (Tomkovich 1997).
In South Korea, after the loss of the important Saemangeum stopover area and almost all of the tidal-flats in Asan Bay and much of Namyang bay, possibly only five sites nationwide remain internationally important. Of these, only one (the Geum Estuary) currently has a low risk of reclamation, with the other four at risk due to the construction of tidal power plants and barrages, industrial use and urban expansion (N. Moores in litt. 2009). Benthic food stocks used by the species reportedly crashed at Yalujiang NNR, Liaoning in 2014 and 2015 (D. Melville in litt. 2015). In 2015, most birds departed Yalujiang and moved to northern Bohai, however, it seems unlikely that this site will exist in five years time, owing to extensive reclamation works (D. Melville in litt. 2015). In the Philippines, India and Australia other threats may include mangrove afforestation, habitat degradation caused by intense fishing activities and harvesting of molluscs and bivalves, infrastructure projects, aquaculture, oil spills and invasive alien plant species (Leyrer et al. 2014). The species is also potentially threatened by climate change because it has a geographically bounded distribution: its global distribution is restricted to within c. 10o latitude from the polar edge of continent and within which 20-50% of current vegetation type is projected to disappear under doubling of CO2 levels (BirdLife International unpublished data).
Conservation and Research Actions Underway
It is listed on Appendix I of the Convention on the Conservation of Migratory Species of Wild Animals (CMS) (CMS 2015). Population trends are being monitored in Australia as part of the Monitoring Yellow Sea Migrants in Australia project. The species was recently uplisted to Endangered in Australia. It was designated for Concerted Actions during 2015-2017 at the CMS COP in November 2014 (CMS 2014).
Conservation and Research Actions Proposed
Identify key stopover areas and prevent their reclamation. Continue to monitor population trends. Restore reclaimed wetland sites. Campaign to stop shorebird hunting in Asian countries. Legally protect it in all range states. Survey the breeding grounds for potential threats. Manage roost sites in the species's Australian wintering range to minimise disturbance (Rogers et al. 2006).
26-28 cm, largest Calidris. Breast and flanks heavily spotted black, scapulars with large chestnut spots and blackish tips. Non-breeding adult with paler grey upperparts and breast (Van Gils et al. 2015). Similar spp. Longer bill than Surfbird Aphriza virgata and similar shape to Red Knot C. canutus but larger and with longer bill.
Text account compilers
Butchart, S., Calvert, R., Derhé, M., Ekstrom, J., Malpas, L. & Ashpole, J
Amano, H., Clemens, R., Moores, N., Rogers, D., Crockford, N., Allen, D., Melville, D., Kasambe, R. & Balachandran, S.
BirdLife International (2023) Species factsheet: Calidris tenuirostris. Downloaded from http://datazone.birdlife.org/species/factsheet/great-knot-calidris-tenuirostris on 01/12/2023.
Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://datazone.birdlife.org on 01/12/2023.