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.
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.