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).

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).

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).