Archived 2017 topics: White-headed Duck (Oxyura leucocephala): request for information.

White-headed Duck, Oxyura leucocephala, has a very patchy distribution across Eurasia and into northern Africa. There is a small resident population in Spain, and northern Africa, but the majority of the population is migratory and is found further east, in eastern Europe, central Asia, the Middle East, southern Asia and into China and Mongolia. The population that breeds in southern Russia and central Asia overwinters in areas such as the southern Caspian Sea (predominantly Azerbaijan), eastern Europe, the Middle East and northern Afghanistan and Pakistan (Carboneras and Kirwan 2017). The species is currently assessed as Endangered under criteria A2bcde+4bcde on the basis that mid-winter counts have suggested that the population has undergone very rapid declines (see BirdLife International 2017), with the two most major threats to the species being the drying of wetlands either through drought/climate change or anthropogenic wetland drainage and hybridisation with the invasive Ruddy Duck (Oxyura jamaicensis) (Green and Hughes 1996, 2001, Hughes et al. 2006, Muñoz-Fuentes et al. 2007).

Data collected as part of the European Red List of Birds led to the species being listed as Endangered in Europe (BirdLife International 2015), predominantly as a result of large declines in the breeding population in Turkey. However, it should be noted that data from the International Waterbird Census in the African-Eurasian Flyway shows that the population the population has been stable since the start of the 1990s, with the declines occurring before this (Wetlands International 2014); and European over-wintering figures (which will include individuals from the breeding populations of central Asia) overall were classed as stable in BirdLife International (2015), with many countries listed as having population fluctuations.

This is in part supported by data from the draft Species Status Report (Orueta 2016), but there is also quite some disparity between this report and the European Red List. For instance, Azerbaijan (stated as a major over-wintering site for populations in Carboneras and Kirwan 2017) is shown by Orueta (2016) to have had only 678 individuals during mid-winter counts in 2013, compared to 2,136 individuals in 2012 and no individuals in 2011; whereas BirdLife International (2015) gives an over-winter estimation of 5,000-10,000 individuals in this country (estimate from 2014). These mismatches make it very difficult to accurately assess trends, and they strongly suggest that these country-wide fluctuations may not be solely down to changes in population size. One alternative explanation may be that there is inter-annual variation in over-wintering sites (see Kear 2005), and this again makes assessing population trends based on winter counts very difficult, as repeated measures at one site will not necessarily be representative of any global trend.

Co-ordinated global surveys during winter would aid in better estimating population trends, but these come with the associated difficulties both financially and logistically. Attempting a global trend analysis using current figures, as presented by Orueta (2016) gives a decline of 34.4% between 2005 and 2013, which would equate to a decline of 61.3% over 3 generations (18 years), and would fall within the range for Endangered, i.e. as the species is currently listed. However, given that the global total number of individuals in the 2013 mid-winter count was only 4,635 individuals this suggests that a lot of individuals were missed during these surveys (as Azerbaijan alone was estimated to have 5,000-10,000 individuals over-wintering in 2014 [BirdLife International 2015]). Support for the idea that many individuals are missed during these counts comes from the fact that a census in Uzbekistan has found >5,000 birds (Li et al. 2006), and only last year co-ordinated counts in Kazakhstan located >20,000 individuals (ACBK 2016). While some of these Kazakhstan birds will potentially migrate to known sites, and may be picked up during other mid-winter surveys, it is obvious that a large proportion of the population is not being recorded. This, once again, makes deciphering population trends very difficult, if not impossible, without further information.

Could country-wide population declines be the result of individuals moving to other localities, rather than indicative of an actual decline in numbers of individuals? Where do these previously unrecognised individuals go/breed? Is there any information regarding the potential trends of Kazkahstan breeding individuals or individuals stopping over there during migrations? Further work is going to be required to answer some of these questions, but we urgently request any further information or comments regarding this species, so as to better assess this species’s global Red List status.

 

References

ACBK. 2016. More than 20 thousand individuals of white-headed duck were registered in Akmola region. http://www.acbk.kz/en/news/7320/ (accessed 13/04/2017).

BirdLife International. 2015. European Red List of Birds. Office for Official Publications of the European Communities, Luxembourg.

BirdLife International. 2017. Species factsheet: Oxyura leucocephala. Downloaded from http://www.birdlife.org on 13/04/2017.

Carboneras, C.; Kirwan, G. M. 2017. White-headed Duck (Oxyura leucocephala). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/52935 on 13 April 2017).

Green, A. J.; Hughes, B. 2001. White-headed Duck Oxyura leucocephala. In: D.B. Parkin (ed.), BWP Update: the journal of birds of the Western Palearctic, Vol. 3, No. 2, pp. 79-90. Oxford University Press, Oxford.

Green, A. J.; Hughes, B. 1996. Action plan for the White-headed Duck (Oxyura leucocephala). In: Heredia, B.; Rose, L.; Painter, M. (ed.), Globally threatened birds in Europe: action plans, pp. 119-145. Council of Europe, and BirdLife International, Strasbourg.

Hughes, B.; Robinson, J. A.; Green, A. J.; Li, Z. W. D.; Mundkur. T. 2006. International single species action plan for the conservation of the White-headed Duck Oxyura leucocephala. CMS/AEWA, Bonn, Germany.

Kear, J. 2005. Ducks, geese and swans volume 2: species accounts (Cairina to Mergus). Oxford University Press, Oxford, U.K.

Li, Z. W. D.; Mundkur, T.; Kreuzberg-Mukhina, E. A.; Yerokhov, S.; Solokha, A.; Ali, Z.; Chaudhry, A. A. 2006. Conservation of the White-headed Duck Oxyura leucocephala in Central and South Asia. Waterbirds around the world. Eds. G.C. Boere, C.A. Galbraith & D.A. Stroud. The Stationery Office, Edinburgh, UK. pp. 624-628.

Muñoz-Fuentes, V., Vila, C., Green, A.J., Negro, J.J. and Sorenson, M.D. 2007. Hybridization between white-headed ducks and introduced ruddy ducks in Spain. Molecular Ecology 16(3): 629-638.

Orueta, J. F. 2016. First Draft Status Report for White-headed Duck Oxyura leucocephala. Report of the Action A6, Project LIFE EuroSAP. SEO/BirdLife Spain (unpubl. report). http://www.trackingactionplans.org/SAPTT/downloadDocuments/openDocument?idDocument=45

Wetlands International. 2014. Waterbird Trends 1988-2012. Results of the trend analyses of data from the International Waterbird Census in the African-Eurasian Flyway. Wetlands Internaional, Ede, Netherlands.

 

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6 Responses to Archived 2017 topics: White-headed Duck (Oxyura leucocephala): request for information.

  1. James Westrip (BirdLife) says:

    MaMing has provided the following comment:

    Only 40-100 White-headed Ducks bred in China, the number has fallen very rapidly in the last 10 years, such as habitat loss, poaching and destruction of nests are the main problem.

  2. I am afraid the coverage of the International Waterbird Census across the range of the species (except Spain) is insufficient to reliably estimate the size or assess the trend of a species that shows very large fluctuations and can abandon sites after a few years.

    Simply comparing the national IWC count totals is not advisable because that do not account for sites not counted (which is very high in the region due to various reasons such as fluctuating financial resources, limited capacity, permits, war, etc.) and shifts in distribution. E.g. 2013 was a year with rather low coverage in Azerbaijan. Important sites like Lake Hajigabul and the Gyzylagach Nature reserve (each holding 2-3 thousand birds in 2006) were not counted in 2013.

    National estimates may account for some of the missing counts, but they tend to cover a longer period and may represent double counting. E.g. the estimate of 5-10 thousand individuals for Azerbaijan are supported by the counts in 2006 and 2007 (8,233 and 5,864 individuals respectively). Therefore, most likely a significant proportion of the population is missed during the mid-winter counts in the East Mediterranean, Turkey & SW Asia population. Likewise, significant portion of the population were missed in the Algeria and Tunisia until recently.

    It is also not helpful simply eyeballing the results of formal trend analyses that take account for missing counts. Although the Nagy et al. (2014, https://www.wetlands.org/download/7762/) assessed the short-term as uncertain fluctuating for the period of 2003-2012, Table 2 shows that there was a predominantly declining trend (growth rate 0.9392, SE 0.0337) also in this period (i.e. the decline has not stopped at the beginning of the 1990s as the description above suggests). Actually, this indicates a faster decline than the overall trend for the 1988-2012 period (0.9607 SE 0.0104). The preliminary results of the IWC trend analysis for the period of 1991-2012 suggests a stable or rather fluctuating trend (1.0179 SE 0.0271) for the period of 1991-2015 while still indicates some statistically not significant decline (0.9843 SE 0.0814).

    We should also take into account that the species also suffers from a continued breeding range contraction on the western edge of its distribution (e.g. Turkey).

    • Jorge F. Orueta says:

      Thank you Szabolcs for your contribution.
      My opinion is that winter censuses could be a very useful tool, but too much limited because of the difference of proportional effort that could be done in each country, and in this case have shown their limits.
      Spain has a relatively modest surface compared to some other countries in the distribution range and a high concentration of ornithologist, universities and research centers, so the distribution is well known and little surprises could be expected. On the other hand, countries with a huge surface as Kazakhstan have shown the magnitude of our knowledge gaps. Russia, Iran are very likely to give big numbers during breeding and wintering, when means are available (census, surveys, isotope analysis, etc.)

  3. Richard Porter says:

    I presume that the high winter counts from Syria – Sabkhat al Jabboul – in the previous decade are available to the assessment team? I had 977 there 22-24 November 2007, but I know more were seen in subsequent years.

  4. James Westrip (BirdLife) says:

    There has been some discussion regarding this species on the Duck Specialist Group website, which can be found here;
    http://www.ducksg.org/2017/06/globally-threatened-species/information-sought-for-iucn-red-list-update/

  5. Andy Symes (BirdLife) says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2017 Red List would be to list:

    White-headed Duck as Endangered under criterion A2bcde+4bcde.

    There is now a period for further comments until the final deadline of 4 August, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from the initial proposal.

    The final 2017 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

Comments are closed.