Oxyura leucocephala
white-headed duck

White-headed ducks (Oxyura leucocephala) are the only stifftail Oxyurinii native to the Palearctic. White-headed ducks can also be found in parts of the Oriental region and the Ethiopian region. The largest populations of white-headed ducks are found in Russia, Kazakhstan, Turkey, Iran, Afghanistan, Tajikistan, Turkmenistan, Uzbekistan, Armenia, and Mongolia. Central and east-Asian populations tend to be migratory while populations in Spain and North Africa are non-migratory. There are four main populations of white-headed ducks worldwide: two are decreasing, one is stable, and one is increasing. Of the two populations of wintering birds that are decreasing, one is located in central Asia and has a population of 5,000 to 10,000, and one is located in Pakistan and on the verge of extinction. There is a stable population in North Africa of about 500 birds in the winter and an increasing population in Spain that has increased from 22 birds in 1977 to about 2,500 birds as of 2006. ("Oxyura leucocephala", 2008; "White-headed Duck Oxyura leucocephala", 2009; Green and Hughes, 1996; Hughes, et al., 2006)

White-headed ducks inhabit freshwater lakes as well as alkaline, saline, and eutrophic lakes connected with larger wetland complexes (Birdlife International, 2009). The alkaline lakes inhabited have a pH range of 7.8 to 10, which prevents the lakes from freezing. Breeding sites of white-headed ducks contain dense vegetation and are small and shallow, with depths between 0.5 and 3 m. Wintering sites are usually larger, deeper, and contain less emergent vegetation. There are conflicting views about winter habitat selection of white-headed ducks. Some research suggests that freshwater habitats are chosen more in the winter than in the breeding season. Other research suggests that white-headed ducks prefer deep, alkaline or saline waters in winter. However, there is a general consensus that the availability of insect larvae (Chironomidae) is a key component of habitat selection. Benthic chironomids are reasonably tolerant of eutrophication, so white-headed ducks are more tolerant of eutrophication than many other water birds (Green et al. 1996). ("White-headed duck Oxyura leucocephala", 2004; "White-headed Duck Oxyura leucocephala", 2009; Green and Hughes, 1996; Green, et al., 1996)

White-headed ducks exhibit some sexual dimorphism. Males have white heads with black caps and blue bills, which are enlarged at the base. Females have white faces with dark caps, cheek-stripes and less swollen bills. Both males and females range between 43 and 48 cm in length and both have chestnut-brown bodies. ("White-headed Duck Oxyura leucocephala", 2009)

White-headed ducks are seasonally monogamous. To attract females, male ducks make a low rattling noise. ("White-headed Duck Oxyura leucocephala", 2009; Hughes, et al., 2006)

White-headed ducks breed from April to June in southern Europe and up to a month later in northern Europe. The timing of the breeding period is thought to be because stable water-levels are necessary during incubation of eggs. Because of this requirement, white-headed ducks breed on small, enclosed, freshwater or eutrophic lakes and tend to choose lakes with shallow water, ranging between 0.5 and 3 m in depth. Nests are located over water in emergent vegetation and consist of cupped stands of stems and leaves. Females become sexually mature at one year of age and lay between 4 and 9 eggs at 1.5 day intervals during the breeding period. The incubation period for eggs is between 22 and 24 days. Relative to their body mass, female white-headed ducks lay the largest egg of any waterfowl. After breeding, white-headed ducks undergo a flightless molting period that lasts 2 to 3 weeks before migration to their wintering grounds. They undergo another flightless molt in late winter as well. ("White-headed Duck Oxyura leucocephala", 2009; Green and Hughes, 1996; Hughes, et al., 2006)

Although little is known about parental investment in white-headed ducks, it can be inferred that females invest heavily in their young due to the length of the incubation period. (Green and Hughes, 1996)

Due to a lack of banding information, there are no known data on adult or juvenile survival rates. (Hughes, et al., 2006)

White-headed ducks are diving ducks and are reluctant to fly in general. They prefer shallow margins of lakes in which they can dive repeatedly. They remain submerged for 5 to 7 seconds and dive again within seconds of surfacing. They show very little reaction when shot at, either remaining in a sleeping posture or swimming away slowly and returning a few minutes later, rather than flying away. This behavior is in contrast to their usual response to predators, which involves a head-up-tail-up alert posture. White-headed ducks are very social outside of breeding season. They tend to congregate during winter, with up to 10,000 individual ducks appearing at a particular wintering site, although individual flocks tend to contain about 500 birds. ("White-headed duck Oxyura leucocephala", 2004; "White-headed Duck Oxyura leucocephala", 2009; Green, et al., 1996)

There are no data indicating that white-headed ducks actively defend a territory. Because they are migratory ducks, they do not restrict themselves to a given home range for any part of the year. The most important wintering site in the world for white-headed ducks is the Burdur Lake in Turkey, which has consistently held more than half of all white-headed ducks counted across the duck’s range, with up to 11,000 ducks being counted on the lake at a given time. (Green, et al., 1996)

White-headed ducks are usually silent except during sexual display, when they make a low rattling noise. ("White-headed Duck Oxyura leucocephala", 2009)

White-headed ducks are omnivorous. When studied, food items from at least 27 families of invertebrates and at least 10 families of aquatic plants were identified in the guts of white-headed ducks. The most important food items are chironomid larvae, the abundance of which affects habitat choice. Angiosperm seeds are an important part of their diet, whereas crustaceans and green plant material are of secondary importance. (Green and Hughes, 1996; Sanchez, et al., 2000)

During the breeding season, white-headed ducks construct their nests in emergent vegetation, which helps hide nests from predators. A “roof” may also be formed over the nest by bending down overhead leaves, providing further disguise from predators. In addition, white-headed ducks dive repeatedly, only re-emerging for short periods of time, which aids in their ability to avoid predators. White-headed ducks are preyed on by gulls (Larus species) and brown rats (Rattus norvegicus). In the Tarelo Lagoon in Doñana, Spain, a large number of abandoned white-headed duck nests were observed after predation by brown rats. White-headed duck nests may also be trampled by cattle. Although it is currently illegal to hunt them, white-headed ducks are easy birds to shoot due to their lack of an escape response when facing hunters. In addition to hunting the ducks, their eggs have been collected for human consumption. ("White-headed duck Oxyura leucocephala", 2004; "White-headed Duck Oxyura leucocephala", 2009; Green, et al., 1996; Hughes, et al., 2006)

White-headed ducks eat soft-bodied invertebrates, crustaceans, and aquatic plants. In the lagoons of Cordoba, Spain, the breeding success of white-headed ducks has been negatively affected by the introduction of carp (Cyprinus carpio) into lagoons, because carp directly compete with white-headed ducks for food. (Green and Hughes, 1996)

Before it was banned due to their vulnerable status, hunting of white-headed ducks for meat was commonplace. In addition, the eggs of white-headed ducks are used for human consumption. Subsistence hunting has been cited as an important problem for the conservation of white-headed ducks. (Hughes, et al., 2006)

There are no known adverse effects of white-headed ducks on humans.

White-headed ducks have been threatened by the introduction of ruddy ducks (Oxyura jamaicensis) to the United Kingdom and their subsequent migration across the western Palearctic. Ruddy ducks and white-headed ducks can hybridize to produce fertile offspring. White-headed ducks are suffering from hybridization in the western end of their range. In addition, male ruddy ducks and male hybrids dominate male white-headed ducks during courtship. White-headed ducks have been listed as endangered on the IUCN Redlist since 2000. They are legally protected in many countries and a conservation program in Spain has led to a large population increase in recent years. Ruddy ducks are also being conserved in Spain, Portugal, and France. A program was launched in 2005 to eliminate the population of ruddy ducks in the United Kingdom with the goal of limiting the amount of hybridization between ruddy ducks and white-headed ducks. An extensive European action plan for the conservation of white-headed ducks was published in 2006 (Hughes et al., 2006). Conservation priorities in Europe include the development of policies to control ruddy ducks, promote protection for key wintering sites of white-headed ducks, and monitor the number of white-headed ducks kept in captivity. ("White-headed duck Oxyura leucocephala", 2004; "Oxyura leucocephala", 2008; Green and Hughes, 1996; Hughes, et al., 2006)