Justification of Red List Category
This species is listed as Near Threatened because it is estimated to have undergone a moderately rapid decline over the past three generations (22 years). Over-exploitation in the non-breeding range (in particular in Suriname) may be the principal driver of declines, with eastern-breeding populations also potentially declining due to reduced food supply at key staging sites and changes in arctic breeding habitat, but further information on the rate and drivers of declines is needed.
The population was formerly estimated at 3.5 million individuals, but this was revised downwards to 2.2 million individuals in 2006 (Morrison et al. 2006, A. Lesterhuis in litt. 2009, Andres et al. 2012), assuming annual declines of 5% in 75% of the North American population.
This species is conservatively estimated to have declined at a rate approaching 30% over three generations (22 years). Determining the exact population trajectory is very difficult, but aerial surveys along the coasts of Suriname, French Guiana and Guyana (which may support c.85% of the population wintering on the coast of South America) suggest that the non-breeding population may have declined by c.79% between the early 1980s and 2008 (Morrison et al. 2012), while data from the Bay of Fundy show a 68% decline during southbound migration between 1982 and 2005, with the greatest reductions taking place since the mid 1990s. Preliminary results from surveys off the Brazilian coast (Belem to Baia de Sanadi) in 2011 suggest that declines have also taken place here since 1982, making it unlikely that a southward shift in wintering range accounts for the declines in Suriname and French Guiana (D. Mizrahi in litt. 2011). Long-term population trend indices also suggest that Semipalmated Sandpiper has declined significantly since the 1980s, especially populations migrating along the Atlantic Coast en route to eastern Canadian breeding areas (Mizrahi et al. 2012). Analyses of population trends with migration monitoring data from eastern and central North America for the 35-year period from 1974 to 2009 found trends that were generally negative, but not statistically significant, with counts that decreased between 1985 and 1999, then recovered at least partially through the 2000s (Gratto-Trevor et. al. 2012). However, data from the breeding range suggests that the species was generally increasing or stable in the western and central portions of the range and had an uncertain status in the east (Smith et al. 2012), making the overall picture difficult to determine.
Calidris pusilla is a common breeder in the Arctic and subarctic from far-eastern Siberia (Russia) east across Alaska (USA) and northern Canada to Baffin Island and Labrador (Chandler 2009). In the non-breeding season the species uses coastal estuarine habitats, wintering on the Pacific coast from Mexico to Peru, and on the Atlantic coast from the Yucatan and the West Indies south to central Argentina, with large non-breeding concentrations occurring along the coast of Suriname and French Guiana (del Hoyo et al. 1996, Chandler 2009, D. Mizrahi in litt. 2009). The population was formerly estimated at 3.5 million individuals, but this was revised downwards to 2.2 million individuals in 2006 (Morrison et al. 2006, A. Lesterhuis in litt. 2009; Andres et. al. 2012), assuming annual declines of 5% in 75% of the North American population. Trends are hard to quantify, but aerial surveys conducted along the coasts of Suriname, French Guiana (Morrison et al. 2012) and northern Brazil (D. Mizrahi, unpublished data) suggest that the non-breeding population in the region could have declined by c.80% between the early 1980s and 2008, from c.2 million to c.400,000 individuals; the possibility that there has been a shift in the wintering range seems unlikely but has not been completely ruled out (D. Mizrahi in litt. 2009).
It breeds in high and low Arctic and subarctic wet sedge or heath tundra, often near pools, rivers and lakes (del Hoyo et al. 1996). In the non-breeding season it is mainly coastal, favouring sandy beaches and intertidal mudflats, sometimes also shallow lagoons and saltmarsh (del Hoyo et al. 1996). On migration it is also found at inland wetlands (del Hoyo et al. 1996). Food is mainly chironomid larvae in the breeding season, along with other small invertebrates and seeds. Various small aquatic, marine and terrestrial invertebrates are taken on migration, including horseshoe crab Limulus polyphemus eggs on spring migration in eastern USA (del Hoyo et al. 1996). Makes non-stop flights of up to 4,000 km on migration, with flocks of up to 350,000 gathering at key stopover sites (del Hoyo et al. 1996).
Hunting of shorebirds in northern South America, which is legal in Guyana but illegal in French Guiana and Suriname, is widespread and thus a potential threat to C. pusilla. Shorebirds killed by hunters in Suriname are estimated to number several tens of thousands annually, involving mainly C. pusilla and Tringa flavipes: if 20,000 C. pusilla were removed from a population of two million annually (1% decrease, net after recruitment), the decline would amount to some 26% over 30 years, independent of other mortality, suggesting hunting could be a significant factor in the observed declines (Morrison et al. 2012). Poaching in Suriname may have increased over the last c.20 years owing to improvements in weaponry and transportation. Another potential threat is the harvesting of horseshoe crabs Limulus polyphemus in Delaware Bay, an area which reportedly sees the passage of c.60% of the total population of C. pusilla during the spring migration. The species feeds primarily on horseshoe crab eggs during episodes of rapid mass accumulation, but harvest pressure from 1995-2005 dramatically reduced egg availability (Mizrahi et al. 2012). Significant changes in the intertidal profile, for unknown reasons, have taken place along the coast of the Guianas, although numbers of birds were also lower in areas with no obvious changes in mudflat area (Morrison et al. 2012). Use of pesticides in agricultural areas such as rice fields may affect shorebirds using those habitats directly, and drainage of pesticides into coastal areas and onto mudflats also has the potential to affect shorebirds (Morrison et al. 2012). Small-scale gold mining has increased considerably in the northern South American wintering range, and mercury, which is used in the extraction process and can reach the coast via the rivers, has the potential to affect shorebirds in coastal areas (Morrison et al. 2012). Oil exploration is underway in Suriname and Guyana, with spills representing a further potential threat. Increasing frequency and severity of hurricanes during southbound migration may be causing increased mortality during this period (Morrison et al. 2012). On the Canadian Arctic breeding grounds, the influence of grazing of Snow Geese (Anser caerulescens) and Ross's Goose (Anser rossii) on shorebird habitats is debatable but the effects last for decades (Peterson et al. 2013).
Conservation Actions Underway
No species-specific actions are known. A plan to address the sustainability of shorebird hunting in the Caribbean and northern South America has been developed as part of the Atlantic Flyway Shorebird Initiative, and actions will be implemented where Calidris pusilla occurs. Work on assessing levels of harvest and support for increasing law enforcement capacity are underway as of 2016. An adaptive management plan for Delaware Bay was formally adopted by the Atlantic States Marine Fisheries Commission in 2012. The plan links harvest decisions to information on the welfare of both horseshoe crab and Red Knot Calidris canutus population levels as well as the use of crabs for bait and by the medical industry, and calls for crab harvest levels to be regularly adjusted in response to data on Red Knot and horseshoe crab populations. Monitoring takes place in some of the major wintering, breeding and migration staging areas, but needs to be expanded.
Conservation Actions Proposed
Carry out systematic monitoring in breeding areas, key staging sites and wintering sites. Implement actions to mitigate effects of key threats, in particular mortality from hunting. Increase capacity for better enforcement of hunting regulations and the introduction of these where they do not currently exist. Support adaptive management plan for horseshoe crab harvest in Delaware Bay.
Text account compilers
Butchart, S., Ekstrom, J., Symes, A. & Wheatley, H.
Andres, B., Mizrahi, D., Brown, A. & Lesterhuis, A.
BirdLife International (2021) Species factsheet: Calidris pusilla. Downloaded from http://www.birdlife.org on 26/02/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/02/2021.