Data Zone
Justification of Red List category
This species is listed as Near Threatened as it almost meets the requirements for listing as threatened under criteria A2bcd+4bcd. It has an extremely large range within which global declines of 10-29% are suspected, largely in response to habitat loss and degradation, hunting and disturbance, but perhaps also other as-yet-unidentified threats associated with climate change.
Population justification
Extrapolating data from the Program for Regional and International Shorebird Monitoring (PRISM) surveys on the species' breeding grounds in Canada, Bart et al. (in prep.) estimated a population size of 1.2 million of islandica and rufa combined, a figure nearly 10 times higher than that calculated by Andres et al. (2012). This estimate does not include populations of islandica in northern Greenland. Taxon canutus was estimated by van Roomen et al. (2015) to number c.250,000, but was revised upwards by van Roomen et al. (2022) for the period 2016-2020 to 260,000-275,000; the latter is accepted here but may still be an underestimate based on breeding densities elsewhere (Bart et al. in prep.). Taxa piersmai and rogersi were estimated, respectively, to number 50,000-62,000 and 48,500-60,000 birds (Clemens et al. 2021), while roselaari probably numbers only c.17,000 (Andres et al. 2012). Combining all these estimates, the global population size is thought to number at least 2 million breeding birds, with an upper bound set to 3 million.
Trend justification
Trends vary across populations but a collation of these suggests moderately rapid declines in this species over the past three generations (19 years). The overall trend of Canadian breeding taxa islandica and rufa, which together comprise a majority of the global population, is difficult to determine. Based on extensive counts on the Atlantic coast of North America, Smith et al. (2023) estimated catastrophic declines equivalent to 88.5% over three generations (evidence of population collapse is also provided by Andres et al. [2012] and USFWS [2014]), but van Roomen et al. (2022) estimated that wintering islandica in western Europe had a stable population trend. Taxon canutus, which is estimated to comprise approximately c.10-12% of the species' global abundance, was estimated by van Roomen et al. (2022) to be declining at a rate equivalent to c.54% over three generations, based on an extrapolation of data from between 2011 and 2020. Rogers et al. (2023) also found a stable trend in Australian populations (piersmai and rogersi combined). The population trend of roselaari is unknown, although this population comprises only <1% of the global population.
Combining these data into a single global population trend is hampered by the disparate trends shown by Smith et al. (2023) and van Roomen et al. (2022). Because a very large proportion of the population of rufa/islandica estimated by Bart et al. (in prep.) is thought to comprise European-wintering islandica, the stable trend of van Roomen et al. (2022) is thought to be more representative. Nonetheless, the combination of Smith et al. (2023) and the trend in C. c. canutus (van Roomen et al. 2022) provide evidence of localised rapid population decline, which are thought to have resulted in a global decline of 15-29% over the past three generations. Future rates of decline are highly uncertain and not estimated here; it is plausible that global rates of decline will slow as taxon canutus becomes an increasingly less significant part of the species' global status; alternatively threats (which for this species are not wholly understood) driving population declines in some populations may begin to affect others.
The species has an extremely large range, breeding from Alaska (U.S.A.) across the Arctic to Greenland (Denmark) and northern Russia. It winters on the Atlantic and Pacific coasts of North and South America, north-western Europe, along the west coast of Africa from Tunisia and Morocco down to South Africa, across southern Asia and around Australasia (Van Gils and Wiersma 1996). There are six subspecies: C. c. canutus breeds in central and northern Siberia, the Taymyr Peninsula and possibly Yakutia, wintering in western and southern Africa and south Asia; C. c. piersmai breeds in the New Siberian Islands (Russia) and winters in north-west Australia; C. c. rogersi breeds on the Chukotskiy Peninsula and possibly further west, and winters in Australasia (Van Gils et al. 2017); C. c. roselaari breeds on Wrangel Island (off north-east Siberia) and north-west Alaska, wintering primarily in western Mexico, as well as the coast of south-east U.S.A., southern Panama and northern Venezuela; C. c. rufa breeds in the Canadian low Arctic and winters on the coasts of south Florida, Texas, northern Brazil (15,400 individuals [R.I.G. Morrison in litt. 2015]) and southern South America; C. c. islandica breeds on the islands of the Canadian high Arctic and north Greenland, it winters in western Europe (Van Gils and Wiersma 1996).
The species breeds in the high Arctic (del Hoyo et al. 1996, Piersma 2007, Piersma et al. 2005, Piersma and van Gils 2011) on dry upland tundra including weathered sandstone ridges, upland areas with scattered willows Salix spp., Dryas spp. and poppy, moist marshy slopes and flats in foothills, well-drained slopes hummocked with Dryas spp. (Johnsgard 1981) and upland glacial gravel close to streams or ponds (del Hoyo et al. 1996). The nest is an open shallow depression (Flint et al. 1984) either positioned on hummocks surrounded by mud and water or on stony or gravelly ground or even coastal spits (Johnsgard 1981, Lappo et al. 2012) on open vegetated tundra or stone ridges (del Hoyo et al. 1996). Outside of the breeding season the species is strictly coastal, frequenting tidal mudflats or sandflats, sandy beaches of sheltered coasts, rocky shelves, bays, lagoons and harbours, occasionally also oceanic beaches and saltmarshes (del Hoyo et al. 1996).
During the breeding season it feeds predominantly on insects (mainly adult and larval Diptera, Lepidoptera, Trichoptera, Coleoptera and bees) and crustaceans and hard-shelled prey, as well as spiders, snails and worms (del Hoyo et al. 1996, Piersma et al. 2005). When it first arrives on the breeding grounds, however, the species is dependent upon vegetation (including the seeds of sedges, horsetails Equisetum spp. and grass shoots) owing to the initial lack of insect prey (Johnsgard 1981). Outside of the breeding season the species takes intertidal invertebrates such as bivalve and gastropod molluscs, crustaceans (del Hoyo et al.1996) (e.g. horseshoe crab Limulus spp. eggs) (Karpanty et al. 2006), annelid worms and insects, rarely also taking fish and seeds (del Hoyo et al. 1996). It is a full long-distance migrant that utilises few stopover sites or staging areas (del Hoyo et al. 1996).
Numerous threats have been identified, but the extent to which any of them are driving observed declines is unknown, with much more research needed before threats can be targeted for mitigation.
Climate change has been identified for several shorebird species as a threat that is driving reduced breeding productivity by a number of mechanisms (e.g. Meltofte et al. 2007, Eikelenboom 2016, Kubelka et al. 2018); more research for this species specifically is needed.
The species is exposed to additional threats on its staging and wintering grounds, particularly habitat degradation and conversion. Significant numbers of C. canutus migrate down the Yellow and East China Seas where habitat loss and hunting are plausibly significant threats. The extent of reclaimed land along the Yellow Sea coastline now exceeds the extent of remaining intertidal mudflat (Murray et al. 2014, IUCN 2023), suggesting that this may have contributed greatly to declines in this species (Melville et al. 2016). The rate of habitat lost to land reclamation has slowed since a peak in c. 2013, in particular in recent years due to the promised near-ceasing of land reclamation in China in early 2018 (Melville 2018); however, recent satellite data suggests that the extent of intertidal mudflat has continued to decrease, in large part due to continued reclamations in the Korean Peninsula (IUCN 2023). Mudflats have also continued to degrade in suitability for this species and other shorebirds because of the invasive alien Spartina alterniflora cordgrass, which appears to be spreading; in recent (post 2020) years, this threat has probably driven greater declines than planned land reclamation. In addition to land reclamation, coastal development and a rapid increase in the human population along the coastline of the Yellow Sea has led to widespread degradation of mudflats and coastal habitats used by this species; IUCN (2023) (and references therein) cite the following as additional drivers of mudflat loss and degradation: 'processes such as changes in sediment supply, loss of coastal vegetation associated with development...erosion, redistribution of sediments due to storms, and compaction and subsidence (sinking) caused by subsurface resource and groundwater extraction are also likely to be factors'. Offshore windfarms may have a so far unquantified impact on birds due to collisions (unlikely) and displacement and disturbance of feeding birds (more likely). Disturbance on mudflats by fishermen and others using the mudflats may also be reasonably considered a threat. Hunting is also possibly a significant threat impacting this and other shorebird species on passage (Gallo-Cajiao et al. 2020).
The species is also threatened by the over-exploitation of shellfish (del Hoyo et al. 1996, Goldfeder and Blanco 2006, van Gils et al. 2006, Kraan et al. 2010) which leads directly and indirectly to reductions in prey availability (del Hoyo et al. 1996, Piersma 2007). Across its non-breeding range the species also suffers from disturbance in the non-breeding season as a result of tourism (Goldfeder and Blanco 2006), residential development (Leyrer et al. 2014) foot-traffic on beaches (Burton et al. 2002, Niles et al. 2010, Lilleyman et al. 2016), recreational activities and over-flying aircraft, which together reduce the size of available foraging areas (del Hoyo et al. 1996). In the past, increased harvesting of Horseshoe Crab Limulus polyphemus in Delaware Bay, U.S.A. resulted in reduced prey availability (Baker et al. 2004, McGowan et al. 2011, Leyrer et al. 2014).
Conservation and Research Actions Underway
This species is covered by the general protection regime provided by Article 1 of the European Union (EU) Birds Directive to all naturally occurring wild species in the EU, although it is also listed on Annex II/B of the Directive as a species that may be hunted in several EU Member States. It is also listed on Annex III (protected) of the pan-European Bern Convention, Annex II of the Convention on Migratory Species (CMS) and Annex II of the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA). Across the EU, 251 Natura 2000 sites have been designated for the conservation of this species on passage and in winter (EEA 2024). It is included on the list of priority EU species that can benefit from a higher EU co-funding rate (up to 75%) under the LIFE Programme, although to date (June 2024) the LIFE project database does not list any projects that have taken practical conservation measures specifically for this species. Some habitats along flyway routes are protected. Active management is also underway at some Australian sites to combat cord grass invasion, as well as protective measures implemented to reduce disturbance at roost sites. The Australasian Wader Studies Group, along with BirdLife Australia's Shorebirds 2020 Project and committed volunteers continue to monitor migratory shorebirds within the East Asian-Australasian Flyway (Vine and Maurer 2016). China is investing hundreds of millions of dollars to clear tidal mudflats of Spartina cordgrass, with the aim of eliminating 90% of it by 2025; locally, this has already been successful, for example at Chongming Dongtan National Nature Reserve (Stokstad 2023). The governments of China and South Korea have halted new projects that require or depend upon land reclamation, and across the Korean Peninsula the number of coastal wetlands has increased; moreover in China and South Korea, key areas for migratory shorebirds (including C. canutus) have been identified and prioritised by government and two World Heritage nominations have been made on these grounds (IUCN 2023). Although data on scale or impact are sparse, IUCN (2023) consider that "support for coastal wetland conservation and wise-use appears to have increased over the last decade". There has been a substantial increase in the number of volunteer groups and NGOs helping to monitor the migrations of shorebirds and other waterbirds, as well as increased media coverage and special events, demonstrating enhanced awareness among coastal communities (see also EAAFP 2016). North Korea became a Party to the Ramsar Convention and joined the EAAF Partnership in 2018. In 2021, the 'Regional Flyway Initiative' (RFI) was set up by the Asian Development Bank, with technical support from BirdLife International, with the aim of protecting and restoring priority wetland ecosystems and the associated ecosystem services they provide in the East-Asian Australasian Flyway (EAAF), the most threatened flyway globally. The Initiative is slated for implementation in 10 East, South and South-East Asian countries: Mongolia, China, Bangladesh, Viet Nam, Cambodia, Lao PDR, Philippines, Thailand, Malaysia and Indonesia, all of which are used by C. canutus on northbound and southbound migrations between breeding and wintering areas, and many also for wintering. The RFI will mobilise large-scale financing to support the protection, sustainable management and restoration of at least 50 priority wetlands across ten Asian countries, with an initial financing commitment of $3 billion from the ADB (BirdLife International 2022). Over time, the RFI aims to enhance and expand the existing efforts in conserving and managing priority wetlands identified on the basis of supporting globally significant congregations of migratory waterbirds, and leverage on collaborative opportunities with stakeholders including national governments, civil society organizations, communities, regional organisations like the East Asian-Australasian Flyway Partnership. A large portion of this species' breeding population is covered by PRISM surveys in North America, enabling regular monitoring.
Conservation and Research Actions Proposed
Protect key habitat across its range and ensure that the species is legally protected in all range states (Leyrer et al. 2014). Ensure sites are protected against the threats associated with oil and gas exploration. Recreation, pollution of wetland habitats, land reclamation, infrastructure development and human disturbance at key staging areas needs to be stopped. Include requirements for this species during planning for coastal development, and advocate the restoration of this species' habitat (Threatened Species Scientific Committee 2016). Shellfish fishing at wintering and stop-over habitats needs to be sustainably managed. Continue to aid in the recovery of horseshoe crab populations in Delaware Bay (Niles et al. 2010). Increase awareness of the species. Expand existing monitoring schemes and conduct research into migration patterns and requirements, ecology and threats (Niles et al. 2010, Leyrer et al. 2014, Threatened Species Scientific Committee 2016). In the East Asian-Australasian Flyway, the main action needed for this is the amelioration of threats on its migration. China needs to implement its plan to eliminate 90+% of Spartina cordgrass to prevent further loss of feeding habitat (much has already been lost to land reclamation; IUCN 2023). The discharge of toxic pollutants into coastal wetlands (especially where there are large shorebird congregations) needs to be controlled. Further degradation of mudflats needs to be stopped, including monitoring and preventing detrimental release of riverine sediments and responsible planning of offshore windfarms. Tools are available, such as AviStep (https://avistep.birdlife.org/) to ensure sustainable building of renewable energy infrastructure. Many of these threats, particularly development of coastal wetlands, apply also to the Arabian Peninsula where there is a need for sensible policy-making and implementation to reduce illegal killing and habitat loss (Brochet et al. 2016, de Fouw et al. 2018).
23-25 cm wader. Breeding adult has rich rusty chestnut underparts with blackish-pale/rufous chestnut upperparts. Female has white feathers on underpart and more white on rear belly. Non-breeding adult pale grey above with narrow white fringes on larger feathers, underparts white, with grey barring on breast and flanks (Van Gils and Wiersma 1996). Juvenile somewhat similar to non-breeding adult. Similar spp. Resembles Great Knot C. tenuirostris but larger and rump white barred grey appearing uniform grey with rest of upperparts, and white wingbar more marked.
Text account compilers
Butchart, S., Ekstrom, J., Ashpole, J, Malpas, L., Elliott, N., Everest, J., Berryman, A., Symes, A., Westrip, J.R.S.
Contributors
Balachandran, S., Meltofte, H., Morrison, R.I., Nagy, S., Stroud, D., Szabo, J., Wilson, J., Zöckler, S., van Roomen, M. & Evans, M.
Recommended citation
BirdLife International (2024) Species factsheet: Red Knot Calidris canutus. Downloaded from
https://datazone.birdlife.org/species/factsheet/red-knot-calidris-canutus on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/12/2024.