Archived 2011-2012 topics: Semipalmated Sandpiper (Calidris pusilla): request for information

This discussion was first published on Nov 30 2010 as part of the 2010-2011 Red List update.

Initial deadline for comments: 31 January 2012.

Link to BirdLife species factsheet for Semipalmated Sandpiper

Semipalmated Sandpiper Calidris pusilla is listed as Least Concern on the basis that it does not approach the thresholds for Vulnerable under any of the IUCN criteria. The species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence less than 20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be negative, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (at least a 30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (fewer than 10,000 mature individuals with a continuing decline estimated to be at least 10% over ten years or three generations, or with a specified population structure).

Recent population trends appear to have been negative for this species in many areas, prompting Morrison et al. (2006) to lower the previous population estimate from c.3.5 million to c.2 million. This adjustment was based on the assumptions of an annual rate of decline of 5% in 75% of the North American population, following the results of mark-recapture work in the Bay of Fundy (Hicklin and Chardine unpubl. data in Morrison et al. 2006). The new estimate, however, was later found to be deflated by a lack of data from western and interior regions, and was corrected to over 2.2 million following the extrapolation of densities calculated for breeding populations in the Arctic (per A. Lesterhuis in litt. 2009).

In an analysis of data from the Maritimes Shorebird Survey and the International Shorebird Survey gathered in central and eastern North America, Bart et al. (2007) detected an annual decline of 4% in the numbers of C. pusilla in the North Atlantic region and a 1.7% decline per year in the Midwest. This may not indicate a decline in the total population as once again western populations were not covered and the species could have shifted its migration routes or timing (Bart et al. 2007), although the slight decline in the Midwest region suggests this is unlikely to have been a factor.

Aerial surveys conducted in December 2008 along the coasts of Suriname and French Guiana suggest that the non-breeding population of C. pusilla in this region could have declined by c.80% since the early 1980s, from c. 2 million to c.400,000, which could be serious given that the region may support c.85% of the population of this species wintering on the coast of South America (D. Mizrahi in litt. 2009). So far, the possibility that the species is shifting its geographical preferences during the non-breeding season cannot be ruled out; however, it has been stated that such a shift does not appear to have taken place (D. Mizrahi in Murray 2009).  Fieldwork undertaken in French Guiana and Suriname during January 2009 revealed that the hunting of shorebirds, which is legal in French Guiana but illegal in Suriname, is widespread and thus a potential threat to C. pusilla. A survey carried out in Suriname during 2006 suggested that hunters there take thousands of C. pusilla (A. Spaans per D. Mizrahi in litt. 2009). 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 in Delaware Bay, an area which reportedly sees the passage of c.60% of the total population of C. pusilla during the spring migration (D. Mizrahi in Murray 2009). The species may be suffering due to a decline in the abundance of horseshoe crab Limulus polyphemus eggs, on which they feed during their northward migration; however, the impact of horseshoe crab fishing on shorebirds is a point of contention (Murray 2009).

There is considerable uncertainty inherent in drawing conclusions from regional population trends for a widespread species such as C. pusilla; however, it remains necessary to estimate the likely overall trend for the species. If the population is found to have declined at a rate approaching 30% over 22 years (estimate of three generations) it may be eligible for uplisting to Near Threatened under the A criterion. The species would likely qualify for at least Vulnerable if the estimated overall decline is at least 30% over 22 years. Up-to-date information is requested on this species, in particular the likely population trend and the severity of threats.

Bart, J., Brown, S., Harrington, B. and Morrison, R. I. G. (2007) Survey trends of North American shorebirds: population declines or shifting distributions? J. Avian Biol.: 38: 73-82.

Morrison, R. I. G., McCaffery, B. J., Gill, R. E., Skagen, S. K., Jones, S. L., Page, G. W., Gratto-Trevor, C. L. and Andres, B. A. (2006) Population estimates of North American shorebirds, 2006. Wader Study Group Bull.: 111: 67-85.

Murray, B. T. (2009) Turns out the red knot is not alone in its plight. The Star-Ledger: 1 February 2009. Newark, NJ.

The following manuscript was sent by Brad Andres on 23 January 2012: Calidris pusilla Andres et al. in press (Andres, B. A., C. L. Gratto-Trevor, P. Hicklin, D. Mizrahi, R. I. G. Morrison, and P. A. Smith.  2012.  Status of the Semipalmated Sandpiper.  Waterbirds 35: in press.)

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4 Responses to Archived 2011-2012 topics: Semipalmated Sandpiper (Calidris pusilla): request for information

  1. I concur with the statements made in the summary above. However, I would like to provide some clarification and additional information that I believe is useful in evaluating the current status of Calidris pusilla.

    In February 2010, we conducted a second survey of the Suriname and French Guiana coast. Our 2010 survey occurred in February rather than December, the period of the 2008 survey, to better conform to the timing of the surveys conducted by Morrison and Ross in 1982. Importantly, our results were similar to those from December 2008, but in fact lower. We also included Guyana in the 2010. Although numbers increased markedly since the 1982 surveys, from ~10,000 to ~20,000, this does not account for the dramatic declines in the species observed in the Suriname and French Guiana.

    We recently completed (26 January 2011) an aerial survey of the Brazilian coast, from Belem to Baia de Sanadi, ~300 km east of Sao Luis. Based on the Canadian Wildlife Service surveys in 1982, it appears that this region supported ~200,000 C. pusilla. Preliminary results from the survey suggest that numbers of C. pusilla have declined since the 1982 survey. Given this, it appears that there has not been a geographic range shift in the populations wintering along the northern coast of South America and that the declines observed in Suriname and French Guiana reflect real population changes. In evaluating these results, it is important to acknowledge that the recent surveys I refer to were conducted by Morrison and Ross, thus they are directly comparable to the results from the 1982 surveys they conducted.

    Counts of small calidrids during the aerial surveys conducted by Morrison and Ross in 1982 totaled ~1.75 million in Guianas, not 2 million. That the Guianas support 85% of the C. pusilla wintering in South America, as referred to in the summary, is an estimate we made based on the survey data from Morrison and Ross. Clearly, C.pusilla may occur in regions not covered by the surveys of the 1980s, e.g., Central America, Caribbean basin. However, these populations are likely to be small than those historically wintering in Guianas and Brazil.

    Regarding poaching, Spaans believes that several10s of thousands of C. pusilla are taken annually in Suriname. Given recent observations we made in French Guiana, legal hunting may also be significant, especially in the extensive rice fields near the Mana River, in the extreme western part of the country. Work by GEPOG suggest that many 10s of thousands of C. pusilla use these rice field to roost during southbound migration.

    Given these data, and analyses of migration monitoring data from ISS and MSS, there appears to be strong support for a change in IUCN status to Near Threatened. Clearly, the core wintering population in the Guianas has declined by well over 30% over the last 30 years. This appears to be supported by information collected during migration along the east coast of North America. At the very least, a change in status to Vulnerable should find strong support.

  2. Adam Brown says:

    We have been conducting wetland surveys on the Lesser Antillean island of St. Martin since the winter of 2000-2001. During our first year, we observed 1103 birds. In recent years, we have observed very few of this species, <10 birds in each of the previous five years. Reports on EPIC surveys can be found at: http://www.epicislands.org/Publications.htm

  3. I concur with David’s assessment, with perhaps an emphasis on the eastern segment of the population (if possible). Unlike some species, conditions on the wintering grounds suggest some problems.

    For the 2009 U.S. State of the Birds report, I attempted a meta analysis of datasets that could supply some information on population trends. Most of these were from the eastern US and Canada. Semipalmated Sandpipers had the strongest, negative signal of any species I reviewed. The analysis is posted at for further scrutiny.

  4. Historically, Semipalmated Sandpiper (Calidris pusilla) was one of the most widespread and numerous calidridine species in the Western Hemisphere. It is among the most ubiquitous and abundant breeders in the Arctic and sub-Arctic regions of western Canada and Alaska. However, the species appears to have experienced significant declines over the last three decades (Morrison et al. 2006, Morrison et al. 2012). Population estimates from the early 2000s were approximately 3.5 million individuals (Morrison et al. 2001). In 2006, this estimate was revised downward to approximately two million individuals (Morrison et al. 2006), based primarily on a mark-recapture study from the Bay of Fundy, Newfoundland, Canada (Hicklin and Chardine 2012). Data from this study suggested that SESA populations using the Bay of Fundy during southbound migration declined from 820,000 to 260,000 between 1982 and 2005, with the greatest reductions taking place since the mid 1990s. This represents an overall decrease of 68% that is consistent with a 5% annual decline over 15 years. International Shorebird Survey (ISS) and Atlantic Canada Shorebird Survey (ACSS) data suggest that Semipalmated Sandpipers migrating along the Atlantic Coast have decreased 4% annually (Bart et al. 2007), a rate similar to that suggested by data from the Bay of Fundy. However, declines in the mid-continental flyway population were not significant (Bart et al. 2007); supporting the contention made by Morrison et al. (2006) that declines may be limited to the Atlantic Flyway population.
    Data collected in northern South America over the last three years suggest that the most recent population estimates may need to be revised downward again (Morrison et al. 2012). Aerial surveys of the entire South American coast conducted during non-breeding, non-migratory periods (i.e., boreal winter) by the Canadian Wildlife Service (CWS) in the early 1980s suggested that approximately two million C. pusilla wintered in Guyana, Suriname, French Guiana and northern Brazil, or 90% of all C. pusilla recorded during these surveys (Morrison and Ross 1989). In December 2008, January 2010 and January/February 2011, NJ Audubon Society and biologists from Environment Canada/Canadian Wildlife Service (i.e., Morrison and Ross) resurveyed the entire coastlines of Guyana, Suriname and French Guiana, and the entire coasts of Pará and Maranhão states in northern Brazil. During these surveys, Morrison and Ross recorded approximately 400,000 SESA, suggesting a decline of approximately 80% in their core South American wintering range (Morrison et al. 2012). Given that mangrove and soft-sediment intertidal mud flats, habitats most often used by C. pusilla, are less prevalent to the west (i.e., Venezuala, Colombia) and east (i.e., Brazil’s eastern coast) of this core range, it is unlikely that the declines observed during our surveys can be explained by a shift in geographic range.
    Conditions in Delaware Bay, a hemispherically important spring shorebird staging area in the Western Hemisphere Shorebird Reserve Network (WHSRN), may explain some of the observed declines in C. pusilla and other sandpiper species, like Red Knot (C. canutus) and Ruddy Turnstone (Arenaria interpres). After migrating from South America, individuals must accumulate sufficient energy reserves to migrate to the breeding grounds, survive harsh conditions upon arrival and initiate the breeding cycle (e.g., courtship). While in Delaware Bay, many shorebird species, including C. pusilla, experience periods of rapid mass gain by feed primarily on the eggs of horseshoe crabs (Limulus polyphemus) (Mizrahi and Peters 2009). However, intense harvest pressure on the crabs and loss of spawning habitats in Delaware Bay over the last decade has seriously reduced the crab population, and consequently, the eggs available to shorebirds. Consequently, the ability of C. pusilla to accumulate energy reserves during the staging period has declined significantly since the mid 1990s (Mizrahi et al. 2012), when the peak harvest of horseshoe harvesting began. Importantly, approximately 50% of all C. pusilla migrating north to the breeding grounds are believed to stage in Delaware Bay (Senner 1984). Since 1986, numbers of C. pusilla staging in Delaware during spring migration have declined markedly, (Clark et al. 1991, Clark personal communication). Several investigators suggest that decreased refueling rates during migration staging and stopover periods can have survival consequences (Baker et al. 2004, Pfister et al. 1998).
    Although Delaware Bay appears to be a critical lynchpin for C. pusilla population viability, we believe that legal and illegal hunting along the northern coast of South America is likely having an effect on the viability of several shorebird species. Evidence from band returns and first-hand accounts suggest that migratory shorebirds, including C. pusilla, are being hunted in Guyana, Suriname, French Guiana and throughout the Caribbean Basin, which is likely having a significant effect on population viability. However, the magnitude of this effect is generally unknown. In 2006, Dr. Arie Spaans conducted a survey of hunters and fishermen in Suriname’s coastal zone to ascertain the number and species of birds shot or trapped annually. The study revealed that a wide variety of protected waterbirds were being killed and sold illegally each year, among which were several tens of thousands of shorebirds. Although not the primary target, C. pusilla is numerically the most often killed because it is the most common among all shorebird species. During three seasons of fieldwork in Suriname and French Guiana we witnessed six separate shorebird-hunting incidents. Two of the four Suriname incidents resulted in the death of over 120 SESA and 6 Lesser Yellowlegs. Morrison et al. (2012) estimate that if 20,000 (i.e., likely the minimum taken annually in Suriname) C. pusilla were removed annually from an overall population of two million (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. Hunting shorebirds is legal in French Guiana (Delelis and de Pracontal 2006) and thought to be widespread in Guyana, although how many shorebirds are taken annually is unknown.
    Given the data presented here, there appears to be strong support for a change in IUCN status for the species to Near Threatened. Clearly, the core wintering population in the Guianas has declined by well over 30% over the last 30 years. Support for this conclusion is apparent in the data collected during migration along the east coast of North America. At the very least, a change in status to Vulnerable should find strong support.

    Literature Cited
    Baker, A. J., P. M. González, T. Piersma, L. J. Niles, I. de Lima Serrano do Nascimento, P. W. Atkinson, N.
    A. Clark, C. D. T. Minton, M. Peck and G. Aarts. 2004. Rapid population decline in Red Knots:
    fitness consequences of decreased refueling rates and late arrival in Delaware Bay. Proceedings of the Royal Society B 271: 875-882.
    Bart, J., S. Brown, B. Harrington and R. I. G. Morrison. 2007. Survey trends of North American shorebirds: population declines or shifting distributions? Journal of Avian Biology 38: 73-82.
    Clark, K. E., L. J. Niles and J. Burger. 1993. Abundance and distribution of migrant shorebirds in Delaware Bay. Condor 95: 694-705.
    Hicklin, P. W. and J. W. Chardine. 2012. The morphometrics of migrant Semipalmated Sandpipers in the Bay of Fundy: evidence for declines in the eastern breeding population. Waterbirds 35: in press.
    Mizrahi, D. S. and K. A Peters. 2009. Relationships between sandpipers and horseshoe crabs in Delaware Bay: a synthesis. Pages 65-88 in Biology and conservation of horseshoe crabs (J. T. Tancredi, M. L. Botton and D. R. Smith, Eds.). Springer Science and Business Media, New York.
    Mizrahi, D. S., K. A. Peters and P. A. Hodgetts. 2012. Energetic condition of Semipalmated and Least Sandpipers during northbound migration stopover periods in Delaware Bay. Waterbirds 35: in press.
    Morrison, R. I. G, D. S. Mizrahi, R. K. Ross, O. Ottema, N. de Pracontal, and A. Narine. 2012. Dramatic declines of Semipalmated Sandpipers on their major wintering areas in the Guianas, Northern South America. Waterbirds 35: in press.
    Morrison, R. I. G., B. J. McCaffery, R. E. Gill, S. K. Skagen, S. L. Jones, G. W. Page, C. L. Gratto-Trevor and B. A. Andres. 2006. Population estimates of North American shorebirds. Wader Study Group Bulletin 111: 67-85.
    Morrison, R. I. G., Y. Aubry, R. W. Butler, G. W. Beyersbergen, G. M Donaldson, C. L. Gratto-Trevor, P. W. Hicklin, V. H. Johnston, R. K. Ross. 2001. Declines in North American shorebird populations. Wader Study Group Bulletin 94: 34-38.
    Pfister, C., M. J. Kasprzyk and B. A Harrington. 1998. Body fat levels and annual return in migrating Semipalmated Sandpipers. Auk 115: 904-915.

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