Red Knot Calidris canutus


Justification of Red List category
This species is listed as Near Threatened as it almost meets the requirements for listing as threatened under criteria A2abc+3bc+4abc. It has an extremely large range and six subpopulations across which trends are variable. The population trend of the largest subpopulation, islandica, is unclear as is the trend of roselaari. The rufa and canutus subpopulations have both experienced population declines. Two subpopulations use the East Asian-Australasian Flyway and have experienced significant declines owing to loss of habitat in the Yellow Sea. Should new research resolve uncertainties in the trends of several of these subpopulations the species may warrant uplisting or downlisting.

Population justification
The global population is estimated to number 891,000-979,000 individuals (Wetlands International 2015). The European population is estimated at 15,000-30,000 pairs, which equates to 30,000-60,000 mature individuals (BirdLife International 2015), and the population overwintering in Australia and the Americas have been estimated at 110,000 individuals (Hansen et al. 2016) and 44,763 individuals (Niles et al. 2010) respectively.

Trend justification
The islandica population trend shows a moderate decrease between 2003 and 2012, whilst the long-term trend is fluctuating (Nagy et al. 2014, Wetlands International 2018). However the European Red List of Birds suggests that the population is increasing strongly in the short-term and experiencing a moderate increase in the long-term (BirdLife International 2015). Van Roomen et al. (2014) found the population was stable/fluctuating in the short- and long-term. The canutus population decreased strongly in the short- and long-term (2003-2014 and 1979-2014, respectively) (van Roomen et al. 2014). The roselaari population trend is uncertain, but is possibly declining (Andres et al. 2012).

The rufa population has undergone a significant decline in the last decade (Andres et al. 2012). The number of birds in Tierra del Fuego declined strongly (75% decrease) between 1985-2000 (52,244 individuals) and 2011-2013 (11,385 individuals) (USFWS 2014). Between 2010 and 2015 the population at Tierra del Fuego has varied in the range of 10,000-15,000 individuals (R.I.G. Morrison in litt. 2015). Whilst counts in Delaware Bay showed similarly large declines: 70% decrease between 1981-1983 (59,946 individuals) and 2005-2014 (18,387) (USFWS 2014). 

Approximately 10-14% of the global population uses the East Asian-Australasian Flyway. An analysis of monitoring data from around Australia and New Zealand found that both the piersmai and rogersi populations which use the flyway have experienced strong population declines, estimated at a 57.4% decrease over three generations (Studds et al. 2017). This decrease is supported by a study on adult survival. Survival in north-west Australia in late winter was constantly high however survival during periods away from Australia declined in 2011, with an annual survival rate of 0.67 (Piersma et al. 2016). The study predicts the population will halve within four years. Overall the global population is estimated to be decreasing at a rate of c. 25% in three generations.

Distribution and population

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 main spring staging sites for each of the six subspecies have been identified: Schleswig Holstein Wadden Sea, Germany (C. c canutus); Troms and Finnmark, north Norway and west Iceland (C. c. islandica); Delaware Bay, U.S.A. (C. c. rufa); Bohai Bay, China (C. c. piersmai and C. c. rogersi) and the Yukon-Kuskokwim Delta, Copper River Delta and Grays Harbour/Willapa Bay, U.S.A. (C. c. roselaari) (Hassell et al. 2011, Leyrer et al. 2014).


The species breeds in the high Arctic (del Hoyo et al. 1996) 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) as well as spiders, small crustaceans, snails and worms (del Hoyo et al. 1996). 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).


The species is vulnerable to extensive land reclamation projects that encroach upon important habitat across its range (del Hoyo et al. 1996, Kraan et al. 2010, Leyrer et al. 2014). Loss of intertidal stopover habitats due to reclamation activities in the Yellow Sea region of the East Asian-Australasian Flyway is thought to be driving declines in shorebird populations (Amano et al. 2010, Yang et al. 2011, Leyrer et al. 2014, Melville et al. 2016, Piersma et al. 2016). It is estimated that up to 65% of tidal flats in the Yellow Sea region have been lost over the past five decades, with an annual loss of 1.2% per year since the 1980s (Murray et al. 2014). These losses are attributed to urban, industrial and agricultural expansion within the region with the populations of C. c. piersmai and C. c. rogersi both being threatened by development at key staging sites in Bohai Bay, China (Rogers et al. 2010, Yang et al. 2011, Leyrer et al. 2014). It is threatened by the over-exploitation of shellfish (del Hoyo et al. 1996, Goldfeder and Blanco 2006) which leads directly and indirectly to reductions in prey availability (del Hoyo et al. 1996). Damming of rivers, dredging (which reduces food availability), pollution, aquaculture operations, renewable energy developments, oil exploration and invasion of mudflats by Spartina grasses pose additional threats to key habitats (Goldfeder and Blanco 2006, Niles et al. 2010, Leyrer et al. 2014, Melville et al. 2016). 

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 (McGowan et al. 2011, Leyrer et al. 2014). The species is hunted illegally for example in New Zealand (del Hoyo et al. 1996) and northern Brazil (Leyrer et al. 2014), and potentially in China (Melville et al. 2016). C. c. islandica and C. c. canutus are both huntable in France and hunting of other species can cause disturbance and accidental mortality. The species can also suffer mortality by incidentally being caught in fish traps (Melville et al. 2016). It has been susceptible to avian influenza in the past so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006), although testing since 1992 in northwest Australia has not found any evidence for this disease in the species there (Curran et al. 2014). Climate change induced sea level rise and thawing of permafrost pose threats to intertidal staging areas, non-breeding sites and Arctic breeding areas (Leyrer et al. 2014, Wauchope et al. 2016).

Conservation actions

Conservation and Research Actions Underway
The species is listed on Annex II (B) of the EU Birds Directive. C. c. rufa is listed as threatened under the Endangered Species Act in the U.S.A. (Anon. 2014). In Canada C. c. canutus is listed as of Special Concern, C. c. roselaari is considered Threatened and C. c. rufa is Endangered according to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) (Anon. 2009). In 2014, five subspecies were proposed for listing for Cooperative Action under CMS (C. c. canutus, islandica, roselaari, piersmai, rogersi) (Leyrer et al. 2014). C. c. rufa is on CMS Appendix I. C. c. canutus and C. c. islandica are listed in Column B, category 2a and 2c of the AEWA Action Plan (Leyrer et al. 2014). In Delaware Bay management aims to protect horsehoe crabs, which would increase prey availability there (Niles et al. 2010). Protected areas have been created to protect roosting sites in some areas (e.g. Stone Harbor Point [Niles et al. 2010]). For at least some subspecies local outreach and awareness work has been conducted (see Niles et al. 2010).

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's 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 horsehoe 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).


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., Malpas, L., Symes, A., Westrip, J., Ekstrom, J., Ashpole, J

Wilson, J., Stroud, D., Zöckler, S., Nagy, S., van Roomen, M., Szabo, J., Meltofte, H., Balachandran, S., Morrison, R.

Recommended citation
BirdLife International (2023) Species factsheet: Calidris canutus. Downloaded from http://datazone.birdlife.org/species/factsheet/red-knot-calidris-canutus on 04/12/2023.
Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://datazone.birdlife.org on 04/12/2023.