Data Zone
Justification of Red List category
The large population of Stilt Sandpiper is declining at a rate between 20-29% over three generations and the species is assessed as Near Threatened. This reduction is estimated from migration count data, believed to represent a significant proportion of the global population and reflect a genuine ongoing decline in the number of mature individuals.
The main drivers of the decline are uncertain, though the impact of habitat alteration caused by climate change on tundra breeding species are likely to impact this species along with loss of non-breeding habitat in South America. Changes to conditions at stopover sites may also be important. Actions to protect and restore wet habitat in the non-breeding range and retain and expand undisturbed areas at key stopover locations would likely mitigate some of the recorded reduction, but more direct research into this and other shorebirds' responses to threats across the full seasonal range is required.
Population justification
The population has been estimated at 1.2 million mature individuals (Andres et al. 2012, Bart et al. in prep.). 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.). The final estimate for Arctic Canada was 1,108,326 (Smith et al. in prep.), with an additional c.124,000 for surveyed parts of northern Alaska (Andres et al. 2012), totaling 1,232,326 and rounded to 1.2 million (Bart 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
Previously, based on BBS/CBC data (Butcher and Niven 2007) the population trend was thought to be increasing in North America. However the majority of both the breeding and wintering range of the species are poorly covered by these surveys, and migration surveys are considered to cover a greater portion of the population and consequently generate more reliable trends. Smith et al. (2023) used updated migration count data to estimate a population reduction equivalent to 22.9% over three generations, though with wide confidence intervals between a reduction of 59.4% and an increase of 41%. The rate of reduction is here estimated to fall within the wide band of 0-59%, with the best estimate between 20-29% over three generations to cover the median rate of reduction estimated by Smith et al. (2023). This data is also used in the Avian Conservation Assessment Database December 2023 update (Partners in Flight 2023).
Breeding season data appeared to show moderate declines in the eastern part of the range, for example a reduction of greater than 70% at Churchill (Manitoba) between the 1960s and 1980s, but in contrast rapid increases in the western part of the range, for example at Prudhoe Bay (Alaska) a 300-400% increase occurred between the 1980s and 1990s (Klima and Jehl, Jr. 2020). However this increase at the western edge of the range likely reflects a westwards shift in the distribution as the species was virtually absent from Prudhoe Bay prior to the 1980s (Klima and Jehl, Jr. 2020). There are now data indicating declines in Alaska too, with surveys in the Arctic National Wildlife Refuge recording 6,218 (SE 2,194) in 2002/2004 but only 4,324 (SE 1,469) in 2019/2022 (R. Lanctot in litt. 2024).
The species breeds in the low arctic and subarctic tundra in northern Canada and Alaska (United States of America). It undertakes a long-distance migration to non-breeding areas primarily in wet habitats in interior South America, especially in northern Argentina, but also in Uruguay and southernmost coastal Brazil, and at high-elevation in Bolivia and Peru. Many also winter patchily along the Pacific coast from central Peru north to Sinaloa (Mexico), around the Caribbean and the Gulf of Mexico with some also remaining at the Salton Sea. On passage most pass through the centre of the USA from Louisiana and Texas to North Dakota and Saskatchwan with relatively few recorded on either coast (Klima and Jehl, Jr. 2020).
Stilt Sandpiper breeds in wet tundra, often with emergent vegetation but may nest on slightly drier slopes (Klima and Jehl, Jr. 2020). Favours ponds for foraging year round, usually in freshwater areas (including flooded agricultural fields) but in non-breeding and passage areas also salt evaporation ponds and brackish lagoons (Klima and Jehl, Jr. 2020).
The loss of wetland area in the south east South American grasslands (Miñarro and Bilenca 2008, Brandolin et al. 2013, Piquer-Rodriguez et al. 2018), a key non-breeding area (Fink et al. 2023) is inferred to be causing an ongoing decline in the area and quality of habitat. Impacts from habitat shifts due to climate change on the species' tundra breeding range (Galbraith et al. 2014, Wauchope et al. 2017, Anderson et al. 2023) have also been projected to cause declines in this species and may already be affecting habitat quality.
As a long-distance migrant Stilt Sandpipers are exposed to a variety of threats during their annual cycle, but determining those likely to be driving population reduction is difficult. Impacts from habitat shifts due to climate change on the species' tundra breeding range (Galbraith et al. 2014, Wauchope et al. 2017, Anderson et al. 2023) appear likely to cause declines in this species, but it is unclear if the effects would already be apparent. Anderson et al. (2023) recorded the species apparently moving into the studied area during the period of study, noting that the species was associated with warmer temperatures than other species present, while Galbraith et al. (2014) determined there would be an increased risk of extinction due to loss of breeding habitat under future climate change. Wauchope et al. (2017) used distribution modelling to predict almost zero climatically suitable habitat for the species by 2070 under the RCP 4.5 or RCP 8.5, consistent with the observation of current rapid shifts in occupied area and future loss of breeding habitat, but none of these studies indicated that loss had already occurred that would account for reductions already recorded. Potentially climate change may affect non-breeding and migratory stop over sites as well, but impacts on the breeding habitat appear likely to become most significant in time.
The biggest change within the species' habitat has been the rapid loss and degradation of wetlands in the south-east South American grasslands due to conversion to agriculture, principally annual crops such as soy beans (Miñarro and Bilenca 2008). This area is a key non-breeding site for the species (Fink et al. 2023) and it is likely that the majority of the population visit this area annually. In south east Córdoba province, Argentina approximately 40% of wetland habitat was lost in 20 years to 2007 following canalisation that acted as a trigger for rapid conversion to agriculture (Brandolin et al. 2013), while a pattern of intensification of use appears to be driving conversion of pasture to cropland in the Pampas (Piquer-Rodriguez et al. 2018). Potentially these changes may have impacts on both the amount of habitat available and on prey abundance, hence quality of habitat. Research is needed into the impacts of these habitat changes on the species, and others reliant on these wetlands.
Market hunting of the species was recorded to have caused large population reductions in the 19th century but the practice continues to some extent, predominately during the post-breeding migration in the Caribbean and northern South America (AFSI 2020). The species was assigned a moderately high (score 3 out of 4) index of harvest for the Caribbean (AFSI 2020) but the level of harvest has not been quantified further. None were recorded in markets in Guyana and few (<0.1%) were observed in surveys recording an annual mean of 101,500 individual shorebirds (Andres et al. 2022), but large numbers (10,000-50,000) have been reported during migration in Suriname (Klima and Jehl, Jr. 2020), where the largest shorebird harvest is currently believed to be occurring (AFSI 2020).
Native predators, notably Red Fox Vulpes vulpes, have expanded their range through use of human subsidies from settlements, which have also moved north (Gallant et al. 2019) and are now more abundant within the breeding range of a range of tundra breeding waders (Bart et al. in prep.). It is suspected that rates of nest predation and potentially rates of adult mortality during breeding have increased as a result, but there is no evidence of this as yet.
Conservation Actions In Place
Protected in U.S. and Canada under the 1927 Migratory Bird Treaty Act. Hunting is illegal in many countries within the species range, though there is allowance for subsistence hunting in Brazil and for indigenous people in Canada and the USA (AFSI 2020).
Stilt Sandpiper is monitored via the North American Breeding Bird Survey (BBS) (Ziolkowski Jr. et al. 2022) although this covers only a small proportion of the breeding range; by the Christmas Bird Count (Meehan et al. 2022) which does not cover the main wintering areas; 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).
Conservation Actions Needed
Knowledge of the species' abundance and trends during the non-breeding season is low, and coordinated surveys in non-breeding areas are required. Consequently the effects of land-use change in non-breeding areas on the species' population and individual survival and body condition are not understood, making the identification of key threats to the species problematic. Hunting may be a significant threat, but quantification of the current rate of harvest is needed across a wider area than so far reported through the AFSI (2020). Updated harvest assessments are needed in Suriname but also potentially further west, e.g. Puerto Rico, Dominican Republic, Haiti and Cuba.
Text account compilers
Martin, R.
Contributors
Smith, P. A., Lanctot, R., Ruiz-Guerra, C. & Nunes, A.P.
Recommended citation
BirdLife International (2024) Species factsheet: Stilt Sandpiper Calidris himantopus. Downloaded from
https://datazone.birdlife.org/species/factsheet/stilt-sandpiper-calidris-himantopus on 25/11/2024.
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 25/11/2024.