Eurasian Oystercatcher Haematopus ostralegus has a wide range comprising four flyway populations: H. o. ostralegus breeds from Iceland and Scandinavia east to NW Russia, south through Britain to NW France, with isolated populations in the Mediterranean, and winters on coasts south to W Africa; H. o. longipes breeds from W and C Russia south to the Black, Caspian and Aral Seas, and east to W Siberia, and winters on coasts from E Africa through Arabia to India; H. o. osculans breeds from coastal NE Russia through Manchuria to NW Korea and NE China, and winters in E China; H. o. finschi breeds and winters in New Zealand (Hockey et al. 2013). It is currently listed as Least Concern, because when last assessed it was not thought to approach the thresholds for Vulnerable under any of the IUCN Red List criteria.
Globally, it has an extremely large range in both the breeding season (>9 million km2) and in winter (>2 million km2), and hence does not approach the thresholds for Vulnerable under the range size criteria (B and D2). Its population size is also extremely large (1,004,000–1,160,000 individuals; Wetlands International 2012), 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).
New data collated from across Europe for the European Red List of Birds (BirdLife International 2015) indicate that the species has declined significantly in recent years, and that this decline is ongoing. A combination of official data reported by 27 EU Member States to the European Commission under Article 12 of the EU Birds Directive and comparable data from other European countries, provided by BirdLife Partners and other leading national ornithologists, suggests that both the European breeding and wintering populations are declining overall at a rate of at least 40% over three generations (41.1 years, based on a generation length estimated by BirdLife to be 13.7 years). This corresponds well with the strong declining trend evident in the flyway population of H. o. ostralegus between 1988–2012, based on midwinter counts conducted as part of the International Waterbird Census (Nagy et al. 2014), and with the declining breeding trend reported by PECBMS (the Pan-European Common Bird Monitoring Scheme). Consequently, the species is now classified as Vulnerable at European level (BirdLife International 2015).
The International Wader Study Group (IWSG) recently published a special issue of its journal International Wader Studies on the conservation status of oystercatchers around the world (based on the results of a workshop held in 2006), containing several very relevant papers on population sizes, trends and threats. Combining the results of these studies with the latest European data produces the following global picture:
|Population||Breeds / winters||Size (individuals)||Trend||Sources|
|ostralegus||Europe / S & W Europe & NW Africa||850,000–950,000||Steep decline||BirdLife International (2015), Nagy et al. (2014), van de Pol et al. (2014), van Roomen et al. (2014a)|
|longipes||SE Europe & W Asia / SW Asia & NE Africa||27,000–40,000||Stable||van Roomen et al. (2014b), Sarychev & Mischenko (2014)|
|osculans||NE Asia||11,000||Unknown||Melville et al. (2014)|
|finschi||New Zealand||79,000–130,000||Decline||Sagar & Veitch (2014), Wetlands International (2012)|
|Total||Global||967,000 – 1,131,000||Decline|
Based on these figures, H. o. ostralegus comprises around 85% of the global population, so the declines in Europe are globally significant. The population of H. o. ostralegus increased strongly between the 1960s and the 1990s (van de Pol et al. 2014), but has subsequently declined significantly, at a rate exceeding 40% over three generations. The decrease in the Netherlands is attributed largely to overexploitation by mechanical shell-fisheries, although additional factors such as agricultural intensification and reduced eutrophication are likely to also have contributed; the causes for the decreases in Germany and Denmark are less well understood and urgently require further study (van de Pol et al. 2014). The population of H. o. finschi (comprising around 10% of the global population) has also started to decline since c. 2000 (Sagar & Veitch 2014). Neither of the other two flyway populations is increasing, and both are very small. Overall, therefore, the species appears to qualify for uplisting to globally Vulnerable under criterion A.
Comments on this proposal are welcome, along with any other relevant data, or information on threats.
BirdLife International (2015) European Red List of Birds. Luxembourg: Office for Official Publications of the European Communities. http://www.birdlife.org/datazone/info/euroredlist
Hockey, P., Kirwan, G.M. & Boesman, P. (2013). Eurasian Oystercatcher (Haematopus ostralegus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2013). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. www.hbw.com
Melville, D. S., Gerasimov, Y. N., Moores, N., Yat-Tung, Y., & Bai, Q. (2014). Conservation assessment of Far Eastern Oystercatcher Haematopus [ostralegus] osculans. International Wader Studies 20: 129-154. http://www.waderstudygroup.org/article/1630/
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. http://www.wetlands.org/Portals/0/TRIM%20Report%202014_10_05.pdf
van de Pol, M., Atkinson, P. W., Blew, J., Crowe, O., Delany, S., Duriez, O., et al. (2014). A global assessment of the conservation status of the nominate subspecies of Eurasian Oystercatcher Haematopus ostralegus ostralegus. International Wader Studies 20: 47-61. http://www.waderstudygroup.org/article/1617/
van Roomen, M., van Winden, E. & Langendoen, T. (2014a) 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. http://www.wetlands.org/Portals/0/EAF_selection%20of%20species2014_2.doc.pdf
van Roomen, M., Langendoen, T., Amini, H., de Fouw, J., Mundkur, T., Thorpe, A., & Ens, B. J. (2014). Population estimate of Haematopus ostralegus longipes based on non-breeding numbers in January. International Wader Studies 20: 41-46. http://www.waderstudygroup.org/article/1615/
Sagar, P. & Veitch, D. 2014. Conservation assessment of the South Island Oystercatcher Haematopus finschi. International Wader Studies 20: 155–160. http://www.waderstudygroup.org/article/1632/
Sarychev, V., & Mischenko, A. (2014). Conservation assessment of Haematopus ostralegus longipes. International Wader Studies 20: 33-40. http://www.waderstudygroup.org/article/1612/
Wetlands International (2012) Waterbird Population Estimates: 5th edition. wpe.wetlands.org