Current view: Data table and detailed info
Taxonomic note
Calidris subruficollis (del Hoyo and Collar 2014) was previously placed in the genus Tryngites.
Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: http://www.aerc.eu/DOCS/Bird_taxa_of_the_WP15.xls.
Christidis, L. and Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. CSIRO Publishing, Collingwood, Australia.
Cramp, S. and Simmons, K.E.L. (eds). 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
SACC. 2005 and updates. A classification of the bird species of South America. Available at: https://www.museum.lsu.edu/~Remsen/SACCBaseline.htm.
IUCN Red List criteria met and history
Red List criteria met
Red List history
| Migratory status |
full migrant |
Forest dependency |
does not normally occur in forest |
| Land-mass type |
continent
shelf island
|
Average mass |
- |
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.
Country/territory distribution
Important Bird and Biodiversity Areas (IBA)
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.
