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The global population of Maccoa Duck Oxyura maccoa is listed as globally Near Threatened owing to perceived ongoing declines resulting from a variety of threats. It is not known if the perceived decline is sufficient for the species to qualify as globally Vulnerable. The regional assessment follows the global assessment.
The Maccoa Duck, despite having a large distribution, is a localised, relatively scarce species confined to several African states in three disjunct populations in the Ethiopian Highlands, East Africa and southern Africa (Scott and Rose 1996). The two northern populations include the countries of Eritrea, Ethiopia, Kenya and Tanzania with the southern population being distributed across Angola, Botswana, Lesotho, Namibia, Zimbabwe and South Africa. The species is a vagrant to Swaziland (Parker 1994). Within the region, the species occurs in large numbers (391-700 individuals) at sites in Mpumalanga, Free State and Western Cape provinces with smaller numbers being recorded in KwaZulu-Natal, Gauteng, Limpopo, North West, Northern Cape and Eastern Cape provinces. The species is largely sedentary, making short post-breeding dispersals, presumably in response to changing environmental conditions (Clark 1964, Kear 2005) although these movements are not well understood (Abebe et al. 2007). Only c. 20% of the regional population occurs within protected areas (Berruti et al. 2005). The species is well represented in the regional IBA network, occurring at a total of 22 sites throughout the region.
The global population is estimated to be 9 000-11 750 individuals which translates to 6 000-7 900 mature individuals (BirdLife International 2014) with the northern population consisting of c. 2 000-3 500 individuals and the southern population c. 7 000-8 250 individuals (Berruti et al. 2005, Abebe et al. 2007). Western Cape Province is estimated to have the highest number of birds (2 148) followed by Mpumalanga (1 125) and Free State (1 125) provinces with the remaining provinces contributing the balance (Abebe et al. 2007). The regional population is lower than previously thought (Abebe et al. 2007), presumably due to a lack of adequate data. The regional population is currently estimated to be between 4 500-5 500 individuals (Abebe et al. 2007). The confidence in this population estimate is medium.
The global population trend is decreasing although the exact rate of decline is unknown. The northern population has suffered perceived declines of up to 50% over the past 10 years (Abebe et al. 2007). The regional population is thought to be stable (Berruti et al. 2005) with populations increasing during the twentieth century due to the occupation of artificial impoundments in Namibia, Botswana and areas of South Africa (Abebe et al. 2007). Despite such increases there are no indications that this growth has continued and Abebe et al. (2007) mention that the trend may have been reversed with a regional decline underway, although the rate of decline is unknown. The confidence in the regional population trend estimate is high.
Key threats to the regional population are the draining of wetlands, pollution, alien vegetation and variable water levels (Abebe et al. 2007). Habitat loss, brought about by the drainage of wetlands and in particular smaller water bodies, which are used by the species for breeding, is a suspected key driver in declines. Pollution, which impacts on these ducks through bio-accumulation, is thought to be having an impact. Variable water levels threaten nests sites (Abebe et al. 2007). Lesser threats in South Africa include entanglement in gill nets, which was identified as a major threat for East African populations (Callaghan and Green 1993), the proliferation of alien vegetation, incidental disturbance through recreational usage of large water bodies, nest predation and poaching (Abebe et al. 2007). An indirect threat has resulted in the increased standard for water quality in the region. For instance, the improved treatment of sewage water at Strandfontein Sewage Work in Western Cape resulted in a decrease in the availability of food, resulting in a decrease from 500 individuals to less than50 at the site (Hockey et al. 1989). Botulism, which occurs on an infrequent basis, has resulted in mortalities of Maccoa Duck in the region. Hybridisation with escapee Ruddy Ducks O. jamaicensis, as well as competition with alien benthic-feeding fish, are perceived threats.
The species is listed under category 1C of the Africa-Eurasian Migratory Waterbird Agreement and under Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals. An International Single Species Action Plan for the Conservation of Maccoa Duck has been compiled. The lead organisation responsible for the drafting of this document is the African Gamebird Research Education and Development Trust (AGRED). A workshop held in 2007 resulted in the formation of a Maccoa Duck Action Group with AGRED as coordinator. Provincial hunting regulations protects the species from hunting in the region.
An inventory of Maccoa Duck sites as well as threats facing individual sites is urgently required. An annual count following a guideline document for population censusing and monitoring is required. The regional population estimate as well as possible rates of declines needs to be ascertained. Key wetland sites need to be protected with an aim to reducing the loss of available breeding habitat. Provincial conservation agencies need to be made aware of threats that entanglement with gill nets poses to Maccoa Duck, and laws against gill netting enforced at key sites. Measures need to be put in place to prevent disturbance at key breeding sites. The correct management of water levels at key breeding sites based upon ecological reserve determination studies is required.
* A desktop study of relevant pollution literature and unpublished data sources is required to assess the impacts of pollution on Maccoa Duck populations.
* The impact that competition from alien benthic fish has on Maccoa Ducks needs to be determined.
* The extent and details of movement of Maccoa Ducks between the breeding and non-breeding seasons needs to be ascertained, with the aim of identifying key conservation sites for this species.