Justification of Red List Category
Despite uncertainty about the possible large-scale inter-year movement of birds between wintering sites, mid-winter counts indicate that the population of this species has undergone a very rapid decline, which qualifies it as Endangered. The total population is now known to be considerably higher than the total recorded during these mid-winter counts, leading to some doubt about the accuracy of global trend estimates calculated solely from winter counts. It is retained as Endangered pending better data from more comprehensive winter counts providing clarity on the overall trend.
The population is estimated to number 2,500 individuals in Spain and Morocco (J. A. Torres Esquivias and A. Green in litt. 2002); 400-600 individuals in Algeria and Tunisia (H. Azafzaf and P. Isenmann in litt. 2002); 5,000-10,000 individuals in the east Mediterranean and south-west Asia, and 10 individuals in south Asia (Wetlands International 2016). This totals 7,900-13,100 individuals, roughly equating to 5,300-8,700 mature individuals. Within Europe the breeding population is estimated at 250-610 pairs, which equates to 500-1,200 mature individuals. The number of wintering birds in Europe is estimated at 7,500-15,900 individuals (BirdLife International 2015). However, a count of over 20,000 individuals were counted on the Tengiz-Korgalzhyn Lakes, Akmola region, Kazakhstan in September 2016 (ACBK 2016).
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). 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 makes deciphering population trends very difficult, if not impossible, without further information. Until a clearer picture can be established, an estimated global decline of 50-79% in three generations is precautionarily maintained. Co-ordinated global surveys during winter are needed to clarify the overall population trend.
This species is resident in Spain, Algeria and Tunisia. A larger population breeds primarily in Russia and Kazakhstan, and also Turkey, Iran, Afghanistan, Tajikistan (likely small and declining [Li and Mundkur 1993]), Turkmenistan (Ritschard and Täschler 2008) (Li and Mundkur 1993), Uzbekistan, Armenia, and Mongolia (believed to be increasing in this latter [Li and Mundkur 1993]) (Green and Hughes 1996). Its status in China is unclear, but it appears to be very rare and declining (Li and Mundkur 1993, Ma Ming 2007a; b, Ma Ming in litt. 2017). It occurs on passage/in winter in the eastern Mediterranean, the Middle East, and central and south Asia.
The global population was probably over 100,000 in the early 20th century, falling to an estimated 20,000 birds in 1996 (Green and Hunter 1996), since then numbers were thought to have declined to around 8,000-13,000 individuals (Li and Mundkur 2003), however a coordinated count of 20,000 individuals in Kazakhstan in 2016 (ACBK 2016) suggest that the previous global estimate was likely too low. Concurrently, breeding populations have become extinct in Italy, France, Hungary, Albania, Yugoslavia, Greece, Israel and Egypt, and probably also in the Ukraine and Armenia. Exact population trends are difficult to calculate given that numbers on wintering grounds often change dramatically in line with altered water availability (Li and Mundkur 1993, Schielzeth et al. 2003, E. Kreuzberg-Mukhina in litt. 2005). At the former key wintering site, Burdur Gölü, Turkey, numbers steadily declined from 10,927 birds in 1991 to 653 in 2001 (M.A. Tabur in litt. 2005). The total Turkish wintering population in 2005 was only 1,006 birds, down from over 9,000 in 1988 (S. Isfendiyaroglu in litt. 2005), with numbers estimated at 868-2,123 individuals for the period 2002-2012 representing a decrease of 60-80% for the same period (BirdLife International 2015). The wintering population in south Asia is mainly concentrated in Pakistan, where it has declined from 1,039 individuals in 1968 to less than 10 in 2002 (Li and Mundkur 1993, A.A. Khan, A. Parveen, and R. Yasmeen in litt. 2005), 33 in January 2003 and 24 in January 2004. It is now only rarely recorded in India (Li and Mundkur 1993).
Increases at wintering sites in Israel (Ohad Hatzofe in litt. 2005), Syria (recent large counts of at least 2,300 birds at Sabkhat al-Jabbul [Balmer and Murdoch 2010]), Greece (Handrinos 1998) and in the Spanish population (22 birds in 1977 to 2,396 in 2000 [J. A. T. Esquivias in litt. 2000], fluctuating to between 1,600-2,600 in 2001-2007 [Ballesteros et al. 2008] and 1,562 in 2008-2012 (BirdLife International 2015) do not compensate for the large declines at Burdur Gölü; and in other eastern populations e.g. Turkmenistan [Li and Mundkur 1993]). Important passage concentrations occur in Uzbekistan (E. Kreuzberg-Mukhina in litt. 1999) and Kazakhstan (Schielzeth et al. 2003, ACBK 2016). There are also reports of very small wintering populations in the Ukraine (0-5 individuals in 1996-2009) (BirdLife International 2015).
Behaviour The Central and east Asian populations of this species are migratory while the populations in Spain and North Africa are non-migratory (Kear 2005). Migrating birds breed from April to July (Sánchez et al. 2000, Kear 2005) (its mating system is unconfirmed) (Kear 2005). After breeding it undergoes a flightless moulting period lasting for 2-3 weeks before it begins the migration to its wintering grounds in late August to arrive September-October (Kear 2005). The return journey commences in February (Johnsgard and Carbonell 1996) and all birds have returned to the breeding range by early May ( Johnsgard and Carbonell 1996, Kear 2005). The species is highly gregarious outside of the breeding season with more than 10,000 gathering at some winter sites, although individual flocks more usually contain less than 500 individuals (Kear 2005). It breeds in single pairs (Kear 2005). In Mediterranean populations, although the species forms congregations at certain sites during the non-breeding season, there is no overall direction to its seasonal movements (Kear 2005) and the location of such non-breeding sites varies inter-annually (Kear 2005).
Habitat Breeding It breeds on small, enclosed, semi-permanent or temporary (Kear 2005) freshwater, brackish or eutrophic lakes with a fringe of dense emergent vegetation (Sánchez et al. 2000, Sebastián-González et al. submitted), often including Phragmites or Typha species, and a covering of pondweeds (Potamogetonaceae) (Johnsgard and Carbonell 1996). It is usually found where these conditions occur within larger wetland systems (Kear 2005, Sebastián-González et al. submitted), and shows a preference for areas with extensive areas of shallow water 0.3-0.5 m deep (Kear 2005). Non-breeding During the winter the species inhabits larger, deeper alkaline or saline waters which often have less emergent vegetation than in the breeding season, but still support algae and pondweeds (Johnsgard and Carbonell 1996). Habitats include saline inland lakes, coastal lakes and lagoons, and even the coastal waters of inland seas (Kear 2005), although it is not found on areas of coast that are subjected to heavy wave action (Johnsgard and Carbonell 1996). In the north-east of its range it is associated with water bodies which are sufficiently saline so as not to freeze over during winter (Johnsgard and Carbonell 1996).
Diet This is a diving duck (Sánchez et al. 2000), its diet consisting predominantly of midge (chironomid) larvae (Sánchez et al. 2000, Kear 2005) and other aquatic invertebrates such as amphipods, isopods and polychaetes (Sánchez et al. 2000) (especially in coastal wintering sites [Kear 2005]). Seeds (Sánchez et al. 2000) and the vegetative parts of Potamogeton spp., Ruppia spp. and other aquatic plants are also be taken (Kear 2005, Johnsgard and Carbonell 1996).
Breeding site The nest is constructed over water in emergent vegetation (usually Phragmites spp. or Typha spp.) (Kear 2005). It consists of a cupped platform of leaves and stems, over which a roof may be formed by bending down overhead leaves (Johnsgard and Carbonell 1996). It will also use old nests of coots or ducks, and has been found to make use of nesting boxes in which it constructs a nest of twigs (Johnsgard and Carbonell 1996).
The greatest long-term threat to the species survival is thought to be competition and introgressive hybridisation (i.e. genetic swamping) with the non-native North American Ruddy Duck Oxyura jamaicensis (Green and Hughes 1996, Green and Hughes 2001, Muñoz-Fuentes et al. 2007). Both male Ruddy Ducks and male hybrids are socially dominant over male White-headed Ducks during courtship (Johnsgard and Carbonell 1996). The threat from the Ruddy Duck is extremely serious, given that, if allowed to proceed beyond a certain point, the Ruddy Duck's spread across the Palearctic will become unstoppable, especially if the species was allowed to become established in White-headed Duck range-states such as Algeria, Turkey or the Russian Federation, where the huge size and area of the wetlands and their infrequent monitoring would make control impossible (Hughes et al. 2006). Climate change is thought to be causing more frequent droughts and drying out of many lakes in central Asia which may be a great threat to the survival of the species. Droughts in Kazakhstan and Uzbekistan may have caused poor breeding seasons in 2002 and 2003 (Li and Mundkur 1993, B. Hughes in litt. 1999).
Approximately 50% of breeding habitat has been drained during the 20th century. Remaining sites are vulnerable to drainage, filling, pollution and disturbance. A 1989 study in the main Pakistani wintering lakes showed that suitable habitat had decreased because of lowered water levels due to reduced water supply, and that fisheries had increased disturbance (A.A. Khan, A. Parveen, and R. Yasmeen in litt. 2005). Water abstraction for agriculture and other uses has affected water levels in many important sites throughout the range. The genetic diversity of the Western European population is low (Muñoz-Fuentez et al. 2005) owing to its having suffered a bottleneck in the 1970s and early 1980s when only a few dozen individuals remained in the wild (Johnsgard and Carbonell 1996, Muñoz-Fuentez et al. 2005). This may lessen the adaptive potential of the population, rendering it less able to withstand environmental change (Muñoz-Fuentez et al. 2005). Further threats include drowning in fishing-nets, hunting and ingestion of lead shot (Green et al. 1996, J. Criado in litt. 1999, Mateo et al. 2001, A.A. Khan, A. Parveen, and R. Yasmeen in litt. 2005). The species is hunted illegally in most of the range states but this has not been quantified, apart from in Turkey. Hunting and egg collection are the most likely reason for extinction in some countries (Hughes et al. 2006).
Conservation Actions Underway
CITES Appendix II. CMS Appendix I and II. The species is legally protected in many range countries, and occurs in a number of protected areas. A conservation programme in Spain resulted in a significant population increase (J. Criado in litt. 1999). Ruddy Ducks O. jamaicensis are controlled in 15 Western Palearctic countries, including Spain, Portugal and France. A programme was started in 2005 to eradicate the UK population of Ruddy Ducks and by 2009, over 6,200 ducks had been culled, resulting in a suggested decrease in the UK population of almost 90% (Henderson 2009). Reintroduction schemes are operational in Majorca and Italy (B. Hughes in litt. 1999, A. J. Green in litt. 2012). A European action plan was published in 2006 (Hughes et al. 2006) and will be revised as part of the Euro SAP project (Ieronymidou 2015). Sport hunting has been banned on two primary wintering lakes (Burdur Gölü and Yarisli Gölü) in Turkey where hunting from speedboats was threatening the White-headed Duck (Green et al. 1996).
Conservation Actions Proposed
Survey breeding and wintering grounds and migration sites. Enforce strict protection from hunting. Conduct comprehensive winter monitoring, and tracking studies to improve knowledge of migration routes and phenology (Li and Mundkur 1993). Protect and manage key sites and their catchments, including monitoring of hydrology and water pollution (M.A. Tabur in litt. 2005). Reduce disturbance by fisheries. Ensure legislative protection for this species in all range states (Li and Mundkur 1993). Alleviate hunting pressure and ban lead shot throughout its range. Prevent drowning in fishing nets by regulating fisheries. Promote policies to control O. jamaicensis and hybrids.
43-48 cm. Chestnut-brown diving duck with long tail, often cocked vertically. Male has white head, black cap and blue bill, swollen at base. Female has pale face with dark cap and cheek-stripe and blackish, less swollen bill. Similar spp. Ruddy Duck O. jamaicensis is smaller with brighter chestnut plumage. Male has more extensive black cap and dark hindneck and female has narrower facial band and browner cap. Both sexes lack swollen base to bill. Hybrid identification can be very problematic. Voice Low rattling noise uttered during display. Otherwise generally silent.
Text account compilers
Westrip, J., Symes, A., Derhé, M., Gilroy, J., Ashpole, J, Ekstrom, J., Malpas, L., Pilgrim, J.
Hughes, B., Yasmeen, R., Esquivias, J., Khan, A., Criado, J., Kreuzberg-Mukhina, E., Green, A., Banik, M., Hatzofe, O., Iankov, P., Parveen, A., Nagy, S., Ming, M., Orueta, J., Tabur, M., Porter, R., Munteanu, D., Isfendiyaroglu, S.
BirdLife International (2021) Species factsheet: Oxyura leucocephala. Downloaded from http://www.birdlife.org on 21/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/10/2021.