Behaviour This species is fully migratory (del Hoyo et al. 1996). It departs its breeding grounds from late-July to September (southward movements continuing into November) and returns from late-May to June (Hayman et al. 1986, del Hoyo et al. 1996). It breeds from May to August in solitary well-dispersed pairs and forages alone or in small loose flocks of up to 30 individuals (Johnsgard 1981, Hayman et al. 1986, del Hoyo et al. 1996). It is gregarious during the winter however, often roosting in large flocks containing up to several thousand individuals (del Hoyo et al. 1996). 

Habitat Breeding The species nests in the high Arctic in both upland and valley locations between the treeline and the coast, utilising dry stony tundra with sedge, moss, lichen, grass or dwarf birch, peat ridges in tundra marshes, dry exposed ridges, riverbanks, raised sand or gravel beaches, and rocky slopes (Johnsgard 1981, del Hoyo et al. 1996, Snow and Perrins 1998). Non-breeding Outside of the breeding season the species frequents intertidal mudflats, saltmarshes, sandflats and beaches of oceanic coastlines, bays and estuaries (Johnsgard 1981, del Hoyo et al. 1996). During migration it may also be found inland on lakes, pools or grasslands (del Hoyo et al. 1996). 

Diet Breeding During the breeding season the diet of this species consists largely of adult and larval insects such as beetles and Diptera as well as some plant matter (e.g. grass seeds and stems) (del Hoyo et al. 1996). Non-breeding When on the coast in its wintering range the species takes marine polychaete worms, molluscs and crustaceans (e.g. crabs, sand shrimps), occasionally also taking insects (e.g. grasshoppers and beetles) or earthworms when in inland habitats on passage (Johnsgard 1981, del Hoyo et al. 1996). 

Breeding site The nest is a shallow scrape on dry ground in exposed, stony sites, neighbouring nests not less than 400 m apart (del Hoyo et al. 1996, Snow and Perrins 1998). 

Management information In the UK there is evidence that the removal of Common Cordgrass (Spartina anglica) from tidal mudflats using a herbicide is beneficial for the species (Evans 1986).

Breeds in Arctic Russia from the Kanin Peninsula to Chukotskiy and Anadyrskaya, and Alaska, USA, to Melville Peninsula and Baffin Island (Canada). Birds winter widely on coastlines of North and South America, Europe, Africa, South Asia, South-East Asia and Australasia, with birds occurring in virtually every country when on migration.

Conservation 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, 370 Natura 2000 sites have been designated for the conservation of this species on passage and in winter (EEA 2024). Some habitats along flyway routes are protected. 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 P. squatarola) 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 P. squatarola 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 organisations, communities, regional organisations like the East Asian-Australasian Flyway Partnership.

Conservation Actions Proposed
Ensure population monitoring continues throughout and its range, and preferably expand it to other regions (particularly in East Asia and wintering grounds in Africa where data coverage is currently patchy). 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). There is an urgent need to understand the threat posed by hunting across its range, particularly in the Americas, Africa and the Middle East, where there is a lack of even descriptive understanding on the extent to which this occurs.