Data Zone
Justification of Red List category
Buff-breasted Sandpiper is suspected to have undergone a moderately rapid to rapid decline which is thought to be driven by habitat loss in non-breeding and/or migratory stopover sites, but changes in breeding habitat due to climate change may also be affecting populations. Rapid to very rapid reductions have been detected from a large network of migration sites in North America, which may reflect a significant reduction in reproductive success. But a decline has also been recorded across large-scale sampling surveys of the breeding range in Alaska. The precision of rate estimates may be poor due to the species’ low side fidelity and annual variation in stopover sites, but there appears reasonable evidence to support that a concerning decline is underway. Greater survey effort has resulted in the population size being revised upwards considerably, hence the species is not believed to be at risk due a small population size at present. Due to the likely rate of population reduction, Buff-breasted Sandpiper is assessed as Vulnerable.
Population justification
The global population has most recently been estimated at 550,000 individuals (Bart et al. in prep.). This value is based on the final estimate from 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 568,395 individuals (95% CI 358,000-654,000) (Smith et al. in prep.), with an additional 42,588 (5,856-79,260) individuals in Alaska (ECCC 2021, Smith et al. in prep.), giving a total of 610,983 individuals (364,000-733,000). The entire Canada and USA range was included within the sampled area (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. However, this estimate has been derived from a low number of survey plots and the habitat strata to which densities are applied are coarse (R. Lanctot in litt. (2024). For this species, which has a lek mating system and fine-scale habitat selection, densities can be highly variable and unpredictable making extrapolations based on habitat association potentially misleading (ECCC 2021). These concerns are emphasised by the low number of observations on which final numbers are based: only 60 observations produced the Alaskan estimate (Smith et al. in prep.), hence the very wide confidence intervals. The previous population estimate was 56,000 individuals (Lanctot et al. 2010, Andres et al. 2012), from a range of 23,000 (Jorgensen et al. 2008) to 84,000 individuals (Norling et al. 2012), later refined to 35,000-78,000 by Andres et al. (2012). Numbers in non-breeding areas also suggest a much smaller population than that generated by the PRISM surveys, or that a large proportion of this breeding population are unaccounted for by surveys to date (McCarty et al. 2020). Surveys of the non-breeding population in southern Brazil recorded approximately 3,400 individuals (Faria et al. 2023): this is a small proportion of the main wintering area.
Given the uncertainty, the population is here placed in a wide range and the best value is considered to fall below that estimated from the PRISM surveys. It seems likely that the true population size is considerably larger than the 56,000 previously estimated. Using the upper bound of the previous values, 84,000 (derived from a single season extrapolation of counts of spring migrants in Texas [Norling et al. 2012]) as a minimum seems actually precautionary: a long stopover duration was used in this calculation where the true value is likely shorter, and shorter stopovers mean that a greater number of individuals have passed through to study area (ECCC 2021). Similarly, estimates from Nebraska's Rainwater Basin of 43,300 (Jorgenson et al. 2008) were based on a longer stopover duration than later estimated at the site (McCarty 2015) and a greater number of individuals likely passed through the site. It is also important to note that a proportion of the population skip these sites, further suggesting the population size considerably exceeds the reported value. Considering the various data, the population is here placed in a band of between 84,000-364,000, representing the minimum number based on extrapolation of counts at spring staging locations (Norling et al. 2012) and the low bound of the estimate based on the PRISM surveys (Smith et al. in prep.).
The population today is considered to have been greatly reduced from historic levels due to 19th century market hunting and the loss of much short-grass prairie from North America (McCarty et al. 2020).
Trend justification
Surveys of migratory stopover locations throughout North America, considered the data that could provide the best insight into the population trend, show a very rapid and accelerating rate of reduction over the past three generations (Smith et al. 2023, PiF 2023, Bart et al. in prep.). The annual trend rate is equivalent to a reduction of 53% (95% confidence intervals of +1 to -82%) for the three-generation period to 2019. However, there are several reasons that the sites monitored do not allow for adequate sampling of the population to place high confidence in this estimated rate of reduction (ECCC 2019). An unknown and likely variable proportion of individuals bypass the well-surveyed areas, resulting in only a small proportion of the population being available to count each year (ECCC 2019). Notably the spatial distribution of migration sites monitored altered between the two periods assessed by Smith et al. (2023). Several sites in the central flyway were only included in the first time period, with considerably reduced numbers of sites in Kansas and Oklahoma, and no survey sites in the post 2010 data in Arkansas, Iowa, Minnisota or the Dakotas (Fig. S2 in Smith et al. 2023). During the post-breeding migration these are key staging areas (Fink et al. 2023). As migration counts typically only record small numbers of this species (only 0.2 individuals were recorded on average in the included surveys in Smith et al. [2023]), it is likely that the majority of individuals were not available to be observed at the sites used. The increased estimate of the global population size supports the notion that only a very small and variable fraction is detected during migration counts (ECCC 2019). Another consideration is that many of the individuals that are recorded are likely to be juveniles, which move across a wider area during their first southbound migration. Rapid reductions in the numbers detected may therefore reflect much reduced productivity (R. Lanctot in litt. 2024). Neither Breeding Bird Survey data or Christmas Bird Count data contain meaningful data on this species. PRISM surveys in the Arctic National Wildlife Refuge in northwestern Alaska showed a non-significant population decline from 2002/2004 (7,684 +/- 5,167 adults) to 2019/2022 (2,386 +/- 1,466) adults (S. Brown et al. unpubl. data, per R. Lanctot in litt. 2024), where the associated probability of a decline was estimated at around 82% (R. Lanctot in litt. 2024).
Evidence of current declines on the wintering areas is equivocal: flocks are highly mobile and switch favoured sites regularly hence are highly unpredictable and difficult to monitor (Lanctot et al. 2002, ECCC 2019, McCarty et al. 2020). Declines on the Estancia Medaland grasslands were apparent from comparisons of data from 1973-4 (Myers 1980) and 1996-2000 (Isacch and Martinez 2003), but subsequently flocks of the size recorded in 1974 were observed there in 2017 (Martínez-Curci et al. 2018). However this site has retained suitable habitat while considerable areas of non-breeding habitat have been converted or degraded, such that being able to detect reductions at this site would not be expected.
Given the uncertainty within the trend data, and that it may be biased high by the geographical shift in sites used, the rate of reduction over the past three generations is placed in a band of 20-49%. This rate of reduction is suspected to continue for the current three generation period that runs one generation length into the future, 2015-2028, based on the apparent recent acceleration in the rate (Smith et al. 2023). The level of uncertainty is considered too high to project further to the future.
The species breeds in the low arctic and subarctic tundra largely in Arctic Canada but also along the north slope of Alaska (United States of America) and in Chukotka, Russia, west to the Ekvyvatap River and Wrangel Island (McCarty et al. 2020). It undertakes a long-distance migration to non-breeding areas in coastal and interior areas of Argentina, and coastal Uruguay and southernmost Brazil. An unknown number winter further inland in Argentina (McCarty et al. 2020, Fink et al. 2023) but it does not regularly winter in Paraguay (R.P. Clay in litt. 2024). Grasslands in north-central Bolivia and Amazonian rivers in Peru appear to be heavily used during the post breeding migration (Fink et al. 2023). The majority of adults use a rather narrow migration corridor and few major stopover sites during the pre breeding migration: the Llanos in Colombia and Venezuela, north coast of the Gulf of Mexico in Texas and Louisiana and sites in the eastern Great Plains, especially the Rainwater basin in Nebraska, and into Canada through Manitoba and Saskatchwan (Lanctot et al. 2002, Jorgenson et al. 2008, Ruiz-Guerra et al. 2013, Lanctot et al. 2016, McCarty et al. 2020, Fink et al. 2023). It is generally scarce but regular in eastern US states on southbound migration and has been widely recorded as a vagrant (McCarty et al. 2020, Fink et al. 2023).
This species breeds in the high Arctic on well drained tundra with tussocks and scant vegetation. It is generally not found near the sea and avoids inundated marshes. It appears to depend heavily upon intensive grazing by livestock in its wintering grounds to create short grassland (Lanctot et al. 2002, Aldabe 2016), but also uses flooded pampas grasslands (Blanco et al. 2004, Lanctot et al. 2004). During migration it is found on many short grass habitats (McCarty et al. 2009, Norling et al. 2012), and appears to have developed a strong association with turf farms in Texas (R. Lanctot in litt. 2024). At the internationally important Rainwater Basin stopover site in Nebraska, U.S.A., it was observed to feed primarily in agricultural land (soybeans, corn), and use wetlands for resting (McCarty et al. 2009). It is a lekking species.
Throughout the non-breeding range and along the species’ migration route the area of suitable natural short grass habitat has decreased enormously since the 1800s and is continuing to be converted to agricultural cropland (Lanctot et al. 2010). While the species has adapted to using a variety of agricultural land that provides short grass habitat (c. 5-8 cm tall, R. Lanctot in litt. 2024), the increasing conversion to row crops and subsequent intensification of management (Piquer-Rodriguez et al. 2018) is inferred to result in an ongoing decline in habitat area and quality. The rapid conversion of savannah to oil palm and rice cultivation in the Colombian Llanos (Romero-Ruiz et al. 2011) undoubtedly reduces the quality and likely the area of habitat available in this key pre-breeding migration staging area (Lanctot et al. 2016, Fink et al. 2023).
Habitat loss in the non-breeding and migratory stopover sites is likely to be one of or the primary drivers of population reductions. The species has proved able to adapt to the conversion of natural grassland to grazed pasture and in migratory stopover sites also uses tilled cropland, including soy beans and corn fields (McCarty et al. 2020). However, the ongoing conversion of grazed land to crops within the limited non-breeding area and subsequent intensification of agricultural management of that land (Lanctot et al. 2010, Piquer-Rodriguez et al. 2018, COSEWIC 2021) is thought to be at sufficient intensity to be causing population impacts. Changes in grazing regime that result in taller vegetation reduce the area of suitable foraging habitat (Lanctot et al. 2010).
The Llanos grasslands, a key pre-breeding migration stopover site (Garcia-Ruiz et al. 2013, Lanctot et al. 2016), are rapidly being converted to oil palm and rice in Colombia (Romero-Ruiz et al. 2011), which are unsuitable habitats for this species.
Habitat shifting caused by climate change is a severe future threat that is considered likely to result in a decline in habitat availability, although current predictions are uncertain (Anderson et al. 2024). What has been demonstrated is that the species is already being lost from some study areas near the south of the breeding range (Andersen et al. 2023), and rapid changes in abundance at some sites appear driven by shifts in the range, noting that the species breeds to the northward limit of land. Using a species distribution model approach Wauchope et al. (2017) predicted that under future climate change scenarios RCP 4.5 and RCP 8.5 Buff-breasted Sandpiper would lose around 50% of climatically suitable breeding habitat by 2070. Climate change may also affect the species during migration by increasing the severity of storms over the western Atlantic that could directly impact survival rates of juveniles, which predominately use this pathway during southbound migration (Lanctot et al. 2010).
The species was severely overhunted in the late 1800s and the early part of the 1900s, reportedly declining to near extinction from a population which may have numbered in the hundreds of thousands to millions (Lanctot et al. 2010, McCarty et al. 2020). Current hunting mortality is poorly known but not thought to be significant and is unlikely to be close to the Potential Biological Removal value set at 921 to 1,847 mature individuals (Watts et al. 2015, McCarty et al. 2020). Hunting mortality does continue in Barbados, though this species is taken inadvertently from mixed flocks and it is strictly protected in the country (Wege et al. 2014). This species is rare in the areas where high levels of shorebird hunting have been recorded recently and is not considered to be at significant risk (AFSI 2020).
Exposure on migration to toxic chemicals and pollutants in its agricultural feeding grounds may pose a threat (McCarty et al. 2020). There is evidence that individuals are exposed to cholinesterase-inhibiting organophosphorus and carbamate pesticides in rice and cattle pastures in Argentina and Paraguay, which affect the birds' physiology (Strum et al. 2010) and may reduce individual condition sufficiently to result in carry over effects on migration and the subsequent breeding season. High levels of chemicals are applied in the turf farms that are now heavily favoured by the species at stopover sites sites along the Gulf of Mexico (R. Lanctot in litt. 2024, McCarty et al. 2020); any population impact of these is uncertain. There has also not been any assessment of the impacts of new classes of agricultural chemicals, such as neonicotinoids (Gibbons et al. 2015).
Conservation Actions Underway
CMS Appendix I and II. Several symposia have been held and the Buff-breasted Sandpiper Conservation Working Group has been formed to identify priority actions and bring together individuals and organisations involved in conservation action and research for the species (Anon. 2020). A conservation plan was prepared for the species in 2010 that lists priority actions for the species (Lanctot et al. 2010). Intensive field surveys are on-going in Texas and Nebraska, and a range-wide tracking study is underway to document migration routes and key staging, breeding and wintering locations (Lanctot et al. 2016). Intensive range management and site conservation are underway in Argentina, Brazil, Uruguay and Bolivia.
Text account compilers
Martin, R.
Contributors
Casañas, H., Harrington, B., Lanctot, R., Russell, R., Dowsett, R.J., Smith, P. A., Clay, R.P., Ruiz-Guerra, C. & Dias, R.A.
Recommended citation
BirdLife International (2024) Species factsheet: Buff-breasted Sandpiper Calidris subruficollis. Downloaded from
https://datazone.birdlife.org/species/factsheet/buff-breasted-sandpiper-calidris-subruficollis 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.