Data Zone
Justification of Red List category
Although uncertain, data from both the non-breeding range and from migration sites indicate that the population has been declining at a moderately rapid to rapid rate potentially exceeding 20% over the past three generations. The population size and range remain large. The drivers of these declines are not well understood, nor are reasons for disparate trends in different parts of its range. As rates of population reduction approach threatened thresholds, Semipalmated Sandpiper is assessed as Near Threatened.
Population justification
The population was estimated as c.2.3 million in 2012 (Andres et al. 2012) but was recently substantially revised upwards to c.9-10 million in Arctic Canada and Alaska (Bart et al. in prep., Smith et al. in prep.). Much smaller numbers breed in Siberian Russia, hence the total global population is estimated at 9-11 million birds. This value is based on the Program for Regional and International Shorebird Monitoring (PRISM) surveys on the breeding grounds (Bart and Smith 2012, Smith et al. in prep.). These surveys target breeding pairs in suitable breeding habitat, hence the values derived are considered to relate to mature individuals.
Trend justification
Difficult to determine, but probably declining, potentially moderately rapidly or rapidly. Recent migration count data from the Atlantic coast indicate potentially rapid declines, albeit with high uncertainty. Smith et al. (2023) estimated a population reduction equivalent to 40.4% over three generations, though with wide confidence intervals between a reduction of 67.4% and an increase of 1.67%. These data are also used in the Avian Conservation Assessment Database December 2023 update (Partners in Flight 2023). Christmas Bird Count (CBC) data also indicate very rapid declines (Meehan et al. 2022). These data broadly match previous suggestion that Atlantic populations are decreasing (Gratto-Trevor et. al. 2012) and documented declines of non-breeding congregations in northern South America (Morrison et al. 2012). However, on the Pacific (west) coast, the Migratory Shorebird Project (unpublished data) estimated that the recent trend is increasing up to 3.78% per year (-11.2 to +18.7), or +54% (-75 to +644%) over three generations. This suggestion matches Smith et al. (2012) who found that populations in the western and central areas of the breeding range are increasing. This pattern of data suggests that population increases in the west are likely to some extent offsetting declines in the east, but the numbers of birds involved is not well established. Overall, the global population is estimated to have declined over the past three generations by 0-40%, with a best guess of 10-26%, assuming approximately 15-30% of birds are using the Pacific coast. More research is however needed.
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 Chile, and on the Atlantic coast from the Yucatan and the Caribbean 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).
This species 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).
Available breeding habitat based on predicted distribution under future climate change scenarios is predicted to reduce by between 6% (RCP 4.5) and 52% (RCP 8.5) by 2070 (Wauchope et al. 2017). Moreover, the expanding range of Red Fox Vulpes vulpes (see also Elmhagen et al. 2017, Gallant et al. 2020) may be causing increased rates of depredation, and hyperabundant Snow Geese Anser caerulescens and Ross’ Geese Anser rossii degrade habitat and cause increased predator densities (see, e.g., Flemming et al. 2019a, 2019b, 2019c).
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 (Morrison et al. 2012). The species has also been recorded as being hunted heavily in Guyana (Andres et al. 2022), leading AFSI (2020) to conclude that hunting pressure on the species in the broader northern South America region is high.
Bart et al. (in prep.) identified coastline development on the non-breeding grounds as a plausible threat, as well as localised oil drilling activities on the breeding grounds.
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). However, this species apparently has a more catholic diet than other shorebird species and is unlikely to be dependent on Limulus eggs.
Conservation Actions Underway
Protected under the Migratory Birds Act (1927). This species' non-breeding population is part-covered by the Christmas Bird Count (Meehan et al. 2022); it is covered by the International Shorebird Survey during migration (Brown et al. 2001, Smith et al. 2023); and partly covered by the International Waterbird Census during the non-breeding season (Wetlands International 2023). Breeding surveys are covered by PRISM monitoring (Bart et al. in prep.). The Eastern Flyway Shorebird Initiative (AFSI) has identified and undertaken a series of measures to address unsustainable harvest in the Caribbean and northern South America (AFSI 2016, 2017, 2020). An initial Potential Biological Removal estimate was generated (Watts et al. 2015) and subsequently a revision using a Prescribed Take Framework has been developed (Rivera-Milán et al. 2023). A preliminary estimate of the harvest in Guyana has been made (Andres et al. 2022), allowing an assessment of annual harvest level against likely sustainable take (Rivera-Milán et al. 2023).
Conservation Actions Proposed
Continue to carry out systematic monitoring in breeding areas, key staging sites and wintering sites to determine ongoing population trends. 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
Ekstrom, J., Symes, A., Berryman, A., Wheatley, H., Butchart, S.
Contributors
Andres, B.A., Mizrahi, D., Brown, A. & Lesterhuis, A.
Recommended citation
BirdLife International (2024) Species factsheet: Semipalmated Sandpiper Calidris pusilla. Downloaded from
https://datazone.birdlife.org/species/factsheet/semipalmated-sandpiper-calidris-pusilla on 22/12/2024.
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 22/12/2024.