Archived 2015 topics: Red Knot (Calidris canutus): request for information

Red Knot (BirdLife factsheet) is a long-distance migrant shorebird, with six Arctic-breeding subspecies:

  • C. c. canutus – CN Siberia, in Taymyr Peninsula and possibly Yakutia; winters in W & S Africa and S Asia.
  • C. c. piersmai – New Siberian Is; winters in NW Australia.
  • C. c. rogersi – Chukotskiy Peninsula and possibly areas farther W; winters in Australasia.
  • C. c. roselaari – Wrangel I (off NE Siberia) and NW Alaska; winters primarily in western Mexico.
  • C. c. rufa  – Canadian low Arctic; winters on coasts of south Florida, Texas, northern Brazil and southern South America.
  • C. c. islandica – islands of Canadian high Arctic and N Greenland; winters in W Europe.

Globally, it has an extremely large range in both the breeding season and in winter, and hence does not approach the thresholds for Vulnerable under the range size criteria (B and D2). Its population size is also extremely large (891,000–979,000 individuals; Wetlands International 2015), and hence does not approach the thresholds for Vulnerable under the population size criteria (C and D1). Therefore, the only potentially relevant criterion is A, which relates to reductions in population size. Until recently, the population was thought to be declining slowly, but not sufficiently rapidly to approach the threshold for listing as Vulnerable under criterion A (at least a 30% decline over ten years or three generations, whichever is longer).

The following summary is based on that in Wetlands International (2015):


Population breeds / winters Size (individuals) % of total Trend and sources
islandica, NE Canada & Greenland/Western Europe 500,000-565,000 55-59% Uncertain
canutus, Northern Siberia/West & Southern Africa 250,000 26-28% Long-term decline
piersmai 50,500-62,000 5-7% Very rapid decline (57.4% in three generations; Garnett 2015)
roselaari 17,000 2% Uncertain; possible decline (Andres et al. 2012)
rogersi 48,500-60,000 5-7% Very rapid decline (57.4% in three generations; Garnett 2015)
rufa 25,000 3% ‘Significant decline’ during 2000s (Andres et al. 2012; USFWS 2014).
Global 891,000-979,000 Moderately rapid decline?



Long-term trend based on International Waterbird Census data is fluctuating; short-term (2003-2012) is moderate decrease (Nagy et al. 2014).

However the European Red List suggests strong increase (1.4-2.95% p.a.) in the short-term (2000-2012) and moderate increase (0.29-0.56%) in the long-term (1980-2012) (BirdLife International 2015).

Using different trend analysis method on the IWC data, van Roomen et al. (in prep) found stable/fluctuating trend both in the short- and in the long-term (Wetlands International 2015). Owing to these conflicting datasets, the overall trend is therefore uncertain.


Based on mid-winter counts, this subspecies underwent a large decrease both in the long- and in the short-term (1979-2014 and 2003-2014, respectively) according to van Roomen et al. (2014). This equates to a decline of some 37% over three generations.


Uncertain; possible decline (Andres et al. 2012).


“Despite the recent variability, numbers remain much lower than the 1980s and 1990s (Dey et al. 2011). Clearly, trends in C. c. rufa demonstrate an overall significant decline in the last decade in all three wintering populations” (Andres et al. 2012).

Average counts for Tierra del Fuego between 1985-2000 (52,244) dropped by about 75% by 2011-2013 (11,385). Comparing four different time periods, average counts in Delaware Bay declined  about 70% overall from 59,946 (1981-1983) to 18,387 (2005-2014), with average counts between those years including 46,886 (1986-1994) and 34,060 (1995-2004) (USFWS 2014). If the population of this form has declined in line with data from Delaware Bay and Tierra del Fuego this equates to a c.55% in three generations.

piersmai and rogersi:

c.10-14% of the global population uses the flyway. BirdLife Australia’s Threatened Species Committee, which applies the IUCN Categories and Criteria at the national level, recently recommended uplisting to Endangered (under criterion A2bc+3bc+4bc) in Australia (Garnett 2015), and the recommendation was subsequently accepted by the BirdLife Australia Research and Conservation Committee. The proposal was based on a detailed analysis of all monitoring data collected on shorebirds around Australia and New Zealand in the last 30 years (Studds et al. in prep) – see extract here:

Annual rate of decline Generation time Loss over three generations Action Plan status 2010 Recommended status 2015
-0.044 6.8 -57.4 Vulnerable Endangered

The analysis used Bayesian binomial mixture models of non-breeding count data throughout Australia and New Zealand to estimate trends for subpopulations thought to follow different migration routes and summarized these estimates to yield flyway-level trends. Count data for each taxon were acquired from local and national databases in Australia and New Zealand. Many counts began in the early 1980s, but several key sites initiated counts in the 1990s.

For shorebirds of the East Asian-Australasian Flyway there is considerable concern that loss of intertidal stopover habitat in the Yellow Sea region of East Asia is driving population declines (Amano et al. 2010; Yang et al. 2011). Up to 65 percent of intertidal habitat in the Yellow Sea has been lost over the past 50 years, and habitat is currently disappearing at a rate of >1 percent annually owing to reclamation for agriculture, aquaculture, and other development (Murray et al. 2014). Current rates of Yellow Sea habitat loss seem likely to continue or accelerate owing to projected human population growth, much of it concentrated along the margins of the Yellow Sea.

Further evidence of genuine very rapid recent decline comes from a study of adult survival in this species, Great Knot and Bar-tailed Godwit along the East Asian-Australasian Flyway. Whereas the survival in NW Australia in late winter remained constantly high, the survival during the time away from Australia started to decline in 2011. With an annual survival rate for Red Knot during 2011-2012 of 0.62, the study predicts that the flyway population of Red Knot will halve within four years (Piersma et al. submitted).

Summary and proposal

Assuming stability of islandica and roselaari, and three-generation declines of 37% in canutus; 57% in piersmai and rogersi, and 55% in rufa, an overall decline of around 25% in three generations may be inferred. This would imply that the species could warrant listing as Near Threatened. However, given the uncertainties outlined above, particularly in relation to the population of islandica (accounting for 55-59% of the global population of the species), it may be appropriate to infer a more conservative rate of decline. Conversely, if there is evidence for decline in populations currently assumed to be stable, the overall rate of decline may be even higher.

Comments on all population size and trend estimates and threats to the species are welcomed, in particular from parts of the range where data are limited.


Amano, T., T. Szekely, K. Koyama, H. Amano, and W. J. Sutherland. 2010. A framework for monitoring the status of populations: An example from wader populations in the East Asian-Australasian flyway. Biological Conservation 143:2238-2247.

Andres, B.A., Smith, P.A., Morrison, R.I.G., Gratto-Trevor, C.L., Brown, S.C. & Friis, C.A. 2012. Population estimates of North American shorebirds, 2012. Wader Study Group Bull. 119(3): 178–194.

Dey, A.D., L.J. Niles, H.P. Sitters, K.S. Kalasz & R.I.G. Morrison. 2011. Update to the status of the Red Knot (Calidris canutus) in the Western Hemisphere, April 2011. Unpubl. report, Manomet Center for Conservation Sciences, Manomet, MA, USA.

Garnett, S. T. 2015. BirdLife Australia Threatened Species Committee report to RACC. 23rd January 2015. Unpublished report.

Murray, N. J., R. S. Clemens, S. R. Phinn, H. P. Possingham, and R. A. Fuller. 2014. Tracking the rapid loss of tidal wetlands in the Yellow Sea. Frontiers in Ecology and the Environment 12:267-272

Nagy, S., Flink, S., Langendoen, T. (2014) Waterbird trends 1988-2012: Results of trend analyses of data from the International Waterbird Census in the African-Eurasian Flyway. Wetlands International, Ede. Report 2014_10_05.pdf

Piersma, T. et al. submitted. Simultaneous declines in summer survival of three shorebird species signals a flyway at risk. PLOS Biology

Studds, C. E. et al. in prep. Dependence on the Yellow Sea predicts population collapse in a migratory flyway.

USFWS. (2014). U.S. Fish and Wildlife Service Protects the Rufa Red Knot as Threatened Under Endangered Species Act: Questions and Answers

Van Gils, J. & Wiersma, P. (1996). Red Knot (Calidris canutus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2014). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from on 23 July 2015).

van Roomen, M., van Winden, E. & Langendoen, T. (2014) The assessment of trends and population sizes of a selection of waterbird species and populations from the coastal East Atlantic Flyway for Conservation Status Report 6 of The African Eurasian Waterbird Agreement.

Wetlands International (2015). “Waterbird Population Estimates” . Retrieved from on Wednesday 22 Jul 2015

Yang, H. Y., B. Chen, M. Barter, T. Piersma, C. F. Zhou, F. S. Li, and Z. W. Zhang. 2011. Impacts of tidal land reclamation in Bohai Bay, China: ongoing losses of critical Yellow Sea waterbird staging and wintering sites. Bird Conservation International 21: 241-259

This entry was posted in Africa, Americas, Archive, Asia, Australia, Central America, Europe & Central Asia, Middle East, North America, South America, Waterbirds. Bookmark the permalink.

14 Responses to Archived 2015 topics: Red Knot (Calidris canutus): request for information

  1. Christoph Zöckler says:

    Considering the evidence you already assembled and the likely decline of islandica as proposed and documented by Nagy et al (2014) and the cautious possible decline but uncertainty raised by Andres et al for rufa I think a listing as NT is justified.

    Further evidence of an continuing overall decline within the species over the past 40 years is given by an analysis of Arctic migratory species initiated by CAFF (Deinet et al. in prep).

    Based on the Living Planet Index (LPI) analysis of a total of 30 time series for the Red Knot the species is declining in all flyways by 15% since 1970s with the sharpest decline combined in the Americas, followed by East Asian populations and also African Eurasian flyways. Although recovering within the latter flyway the overall decline continues and is in line with Nagy et al. (2014).

    Deinet, S., Zöckler, C., Jacoby, D., Tresize, E., Marconi, V. & McRae, L. (2015) The Arctic Species Trend Index for migratory birds. Technical report to the Conservation of Arctic Flora and Fauna.
    Report not yet released but available on the CAFF web site soon!

    The report is not yet released

  2. Dr. Szabolcs Nagy says:

    I think the national Art. 12 reports cannot be legitimately summed up into an overall trend assessment because they cover different periods. So, we can discard that.

    In our IWC trend analysis we have got a short-term decline based on the January IWC data and TRIM, but this is rather minimal (i.e. the slope was 0,9828 S.E. ±0,0064. Marc has got a slope of 1.00 using TrendSpotter. This is a rather minimal difference that arose from using different statistical methods on the same dataset and slightly different interpretation of the results.

    However, for the long-term (i.e. 1988-2012, 25 years what should matter in the Red List assessment), we both got very similar results: our slope was 0,9974 (S.E. ±0,0018), Marc has got a slope of 1.00. Hence, the IWC data shows no evidence of a decline over three generations in the islandica population.

    The declining assessment of Stroud et al. (2009) was based on a longer run of declines in the 1990s but then the population seem to have recovered to earlier levels (see page 214 in the AEWA CSR4

    So, based on the January counts, the population seems to have been fluctuating and not declining in the long-term.

  3. Andy Symes (BirdLife) says:

    Jim Wilson has provided the following comments:

    There are two other ways of getting a «feel» for the population.
    1. Counts on the late spring staging sites in Norway and Iceland around 18-25 May. This will only count the adult population as birds in their second year do not migrate north.
    2. Counts in April on the early spring staging sites. I think it was estimated that 65% of the population was then in the German Wadden Sea. There seems to have been a big drop in numbers in the UK in April and west coast sites there do not seem to be used as much as previously as departure sites to Iceland. Ireland and France are empty of islandica knots in April. Thus the German Wadden Sea might have more knots now than previously. Are there any recent counts there from late April? Or in the Netherlands?

    I have worked with islandica knots on spring migration in N Norway since 2004. In 1992 the population was estimated at 60 000 – 80 000. Wader Study Group Bull 64. Suppl: 121-125. However we believe that this figure is wrong because this is partly based on a count of 60 000 in Porsangerfjord in 1989. I have information that that figure was much too high and the methodology was wrong. The Norwegian staging population is moving northwards and eastwards. Without going into details we estimated the population as maks 60,000 in 2010, but it may have dropped to 40 000 when we lost half the Porsangerfjord population in 2012 (and cannot find the birds again). They may have relocated to Iceland where we have about 70 sightings of Norwegian knots representing many thousand individuals.

    In Iceland there are also big changes with key sites such as Hvalfjordur down from 23 500 in the Atlas of Wader populations to 3000 in recent years – I think the 23 500 figure is prior to the crash in the early 1970s. However there are no total counts through Iceland since the mid-1980s. We counted the NW in 2014 and found a 100% increase there, but only to about 25,000 and there may have been a redistribution because a major site further south was destroyed by a barrage (road crossing).

    I am surprised that there can be 505 000 to 565 000 in Europe in winter. If we reckon that there is an average mortality of 15% then for a stable population there has to be 15% first year birds in the winter. These do not migrate north – so 425,000-480,000 adults should be in Iceland and Norway in May. If we say 60 000 in Norway – then 365,000-408,000 in Iceland – seems high to me based on our trips in 2011 and 2014, but we were mainly in NE and NW. The key sites in Breidarfjordur need counting.

    Comments on count in your mail. Figures from UK are 2004-2008. There must be figures available for every year to winter 2014/2015. As far as I remember from WEBS counts the UK population is stable, so only by changes elsewhere can the population be increasing. There are big winter and early spring movements – westwards after moulting and then eastwards in March and April. Such movements we can also trace through the 600 sightings of flagged birds marked in Iceland and Norway by our team. Without knowing much about Denmark I was surprised to see that there were as many as 27,000 there in winter and also 37,000 in Germany. I thought that birds from those countries had left in mid-winter.
    I assume that UK counts are done at the same time to avoid double counts with movements of birds.

    The population was estimated at 450 000 in Delaney et al 2009. I would be surprised if it has really increased to 500 000 to 565 000. We note possible decreases in Norway and also SW Iceland – but difficult as redistribution is going on.

    I suppose what one really wants to know is if it should be red listed – seems a little doubtful to me – although would very much like because of funding to our project in Norway and Iceland!

  4. Andy Symes (BirdLife) says:

    Hans Meltofte, chairman of the conservation committee of DOF/BirdLife Denmark, has provided the following extract from the draft of a forthcoming paper on Denmark’s most important staging area for waders outside of the Wadden Sea:

    Two Red Knot populations pass Denmark during spring and autumn migration: the North Siberian breeding C. c. canutus that numbers around 400,000 individuals and primarily winters in West Africa, and the likewise high Arctic Greenland/NE Canadian breeding C. c. islandica that numbers around 450,000 individuals and primarily spends the winter in north-western Europe (Meltofte 1993, Delany et al. 2009). There is much uncertainty about the trends in population size in these two sub-species, with the best known C. c. islandica stated as “decreasing” (1980s-2007) by Delany et al. (2009), having long-term “increase” (1983-2007) by AEWA (no year) and showing “moderate decline [check final wording]” (1988-2012) by AEWA (2015). It should be noted, however, that these varying statements follow upon a serious reduction in this population between the early 1970s and the early 1980s (Delany et al. 2009). Due to highly varying numbers recorded on the West African wintering grounds, trends in C. c. canutus are even more uncertain but given as “possibly decreasing” by Delany et al. (2009). The large numbers of Red Knots from both populations passing Blåvandshuk south of Tipperne were stable during 1964-2003 (Meltofte et al. 2006), and so were numbers in the Wadden Sea during 1987-2011; yet with a downward tendency (Blew et al. 2013, JMMB XXXX).

    MELTOFTE, H. & CLAUSEN, P. in print: Trends in staging waders on the Tipperne Reserve, western Denmark, 1929-2014. – Dansk Orn. Foren. Tidsskr. 110.

  5. Andy Symes (BirdLife) says:
  6. Andy Symes (BirdLife) says:

    David Stroud has provided the following comment:

    “From WeBS colleagues at BTO:

    Red Knot must be one of the best monitored waterbirds in the UK given that few are to be found away from sites that are well monitored by WeBS. So virtually a census of this species and so a robust index with minimal imputing. Numbers in the UK fluctuate between about 250K to 300K and this has been relatively stable for quite some time. So the UK holds about half the islandica population, the Waddensea about half with small numbers dotted around elsewhere.

    Looking Watervogels in Nederland 2012/13, the overall trend for the Dutch Waddensea is also apparently stable although the smaller numbers in the Dutch Delta are decreasing. They are increasing in France (Bocher et al. WSGB 2012). Looking at, they are also increasing in the Danish Waddensea and Niedersachsen/Hamburg but decreasing in Schleswig-Holstein. The +ve Danish Trend cancels much of the -ve S-H trend, and the loss in H-S is well within the annual fluctuation of any of the other major concentrations.

    Note that the UK indices are based on the months November to March. I think trends for the Waddensea are based on all 12 months of the year (so would include passage C.c.canutus as well as C.c.islandica. Although IWC indices are based on January data only this can’t explain trend being different, at least for the UK as I have just run off a January Index for the UK to check.

    So I think it is one for the IWC to explain really. Not clear how IWC can be showing a decline when both UK and Waddensea are showing stable numbers.”

  7. Andy Symes (BirdLife) says:

    Szabolcs Nagy has provided the following further information:

    “Just to clarify, we have only reported a short-term (2003-2012) moderate decrease for islandica and this is so small that TRENDSPOTTER would even take it as stable because the different thresholds applied in their and our analysis. (We had to use thresholds compatible with the 25% decline over 7.5 generations).

    For the three generation period both we and Marc’s analysis using January data show stable/fluctuating trend. Hence our assessment of the trend of the wintering numbers is not different from BTOs.

    However, note that contrary to BTO’s statement the Wadden Sea monitoring has reported decline for the Wadden Sea for 1987/88-2011/12, but stable trend for the short-term (2002/03-2011/12). See page 53 here:

    By the way, the same document contains useful information for other wader species under discussion such as the Curlew Sandpiper and puts into perspective some of the comments on the forum.”

  8. Andy Symes (BirdLife) says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2015 Red List would be to treat:

    Red Knot as Near Threatened under criterion A2+3+4.

    There is now a period for further comments until the final deadline of 31 August, after which the recommended categorisation will be put forward to IUCN.

    The final Red List categories will be published on the BirdLife website in late October and on the IUCN website in November, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  9. Dr. R.I. Guy Morrison says:

    I am providing the following information on the rufa population of knots wintering in southern South America, principally in Tierra del Fuego, based on the annual surveys I have carried out. Some additional information is provided for the population wintering in northern Brasil. There appears to be little or no interchange between these populations of rufa – they are distinct units.
    In summary, the TDF rufa population fell from over 50,000 in the 1980s and 2000 to around 10,000 by 2011 and has remained in the range 10,000-15,000 since then – with no signs of any sustained recovery (or further drastic decline). The rufa population is listed as Endangered in Canada.
    The current count of 15,400 in northern Brasil represents the best survey coverage to date (and is not necessarily an increase over previous surveys of the region).
    Although rufa appears to be a small percentage of the overall population of Red Knots, it would appear the current designation of Endangered is appropriate for this group.

    Aerial Surveys of Red Knots in South America – population update for BirdLife International.
    R.I.G. Morrison

    Red Knot Monitoring in Tierra Del Fuego
    1. The count for all sites in TDF was over 50,000 in 1982 (53,232) during the Canadian Wildlife Shorebird Atlas surveys and also in 2000 (51,255), when monitoring was resumed. Counts then fell rapidly to less than 18,000 by 2005 – they remained around this level or slightly less until about 2010. Between 2010 and 2015, counts have varied in the range of about 10,000-15,000 (with lows of 9,850 in 2011 and a high of 14,200 in 2012 and 2014). The most recent count in January 2015 was 12,780. Funding has been provided by Environment Canada. The counts since 2011 suggest that whereas no further major declines have taken place since then, neither has there been any evidence of a sustained recovery.
    2. During the major decline between 2000 and 2005, the trajectory of the counts in the field closely reflected that which would be expected from a reduction in annual survival from about 85% to about 55% as reported by Dr. Allan Baker and coworkers from studies carried out in Delaware Bay.
    3. During the period 2010 to 2015, changes in counts between consecutive years for TDF were -65.1%, +27.9%, -40.5%, +28.8%, and -11.1%. These differences are considerably larger than those between replicate counts (1.1-5.0%, carried out in 2010, 2011, and 2012), and given that the observers and methodology were the same each year, the differences are felt to reflect changes in survival and recruitment, etc., in the population between years.
    4. In 2002, 2003, 2004, and 2012, survey operations included the coastline of Patagonia as well as Tierra del Fuego. These surveys have shown that the decreases in Tierra del Fuego are not due to a redistribution of the birds to other parts of their southern wintering range. In fact, the bulk of the population is now found in Tierra del Fuego: in 1982, some 79% of the southern population was found in Tierra del Fuego – this percentage rose to 93% in 2002, to 98% and 97% in 2003 and 2004, respectively, and was 96% in 2012. This indicates the population can be effectively monitored in Tierra del Fuego.
    5. If the most recent estimate for the coast of Patagonia obtained in 2012 (574) is added to the January 2015 TDF count, the total for the southern part of the wintering range is 13,354.
    Surveys in northern Brasil
    1. In January/February 2013 and 2015, Guy Morrison and Ken Ross carried out surveys of the north and north-eastern coasts of Brasil, from the border with French Guiana to Salvador. Funding was provided by Dr. David Mizrahi of the New Jersey Audubon Society. The total of Red Knots seen on the north-central parts of the coast was 15,625.
    2. The increase in counts in northern Brasil is considered to be due to improved survey coverage rather than an increase in the size of this wintering population.
    The overall current total for aerial survey of Red Knots on the northern and eastern coasts of South America is thus 28,979.
    Dr. R.I.G. Morrison
    10 March 2015

  10. Marc van Roomen says:

    Not really much to add to useful comments about islandica knots already. I think the only real answer on the trend of this subspecies needs to come from analyses of the IWC. All other analyses (UK, Wadden Sea, Tipperne, Norway, Iceland) have the risk to emphasize to much regional trends not representative for the trend in the total flyway population. As already pointed out by Szabolsc, our analyses of islandica trend based on IWC January data from the whole flyway of this subspecies only differs marginally, being slightly decreasing or stable depending on the threshold you use for these statements (our report about the Status of coastal populations in the East Atlantic Flyway will become public on 15 September 2015). If the species is listed as near threatened, this should be based on the decreases in the other populations.

  11. In the 1970s the status Red Knot was considered as a rare vagrant. But in recent years they occur in a few hundreds especially along the East coast of India regularly. It is also recorded from the northwest coast of India. The increase was evident from both sightings and capture data. More numbers are recorded from the south-east coast of India where the subspecies was recognised as rogersi. Though the ringing effort is relatively less in recent yeras when compared to 1970s and 1980s the more number in captures in recent years indicate their increase population. Hence it suggests a possible shift in overwintering grounds. However, I do agree based on its decline from major wintering sites along the other flyways assigning criterion A is more relevant.

  12. David Melville says:

    This discussion highlights the problem of only applying IUCN criteria at the species level – based on European subspecies we can conveniently forget about what is happening to distinct taxa in the EAAF……..

  13. Andy Symes (BirdLife) says:

    Recommended categorisation to be put forward to IUCN

    Following further review, there have been no changes to our preliminary proposal for the 2015 Red List status of this species.

    The final categorisation will be published on the BirdLife website in late October and on the IUCN website in November, following further checking of information relevant to the assessment by BirdLife and IUCN.

  14. Andy Symes (BirdLife) says:

    Szabolcs Nagy has provided the following comment:

    Dear All,

    Just for information, the report on Status of coastal waterbird populations in the East Atlantic Flyway 2014 is now available at This report contains the results of the trend analyses we referred to in earlier contributions.

Comments are closed.