| Citation |
BirdLife International. 2019. Aythya nyroca. The IUCN Red List of Threatened Species 2019: e.T22680373A152620862. https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T22680373A152620862.en. Accessed on 23 March 2022. Brinkman, J.J., van der Ven, W., Allen, D., Hutchinson, R., Jensen, A.E., Perez, C. (2021): Checklist of birds of the Philippines. Wild Bird Club of the Philippines. www.birdwatch.ph |
Description |
JUSTIFICATION
Given that this speciess range may fluctuate considerably from year to year - particularly in Asia - owing to changing water levels, it is very hard to estimate the global population or trends. There have been rapid declines in Europe, but evidence of declines in the larger Asian populations is sparse and sometimes contradictory. The species is currently listed as Near Threatened as it is suspected to be undergoing a moderately rapid overall decline; evidence of rapid declines in Asia would qualify the species for uplisting to Vulnerable, but conversely evidence of stability could lead to its downlisting to Least Concern.
RANGE DESCRIPTION
This species breeds principally in south-western Asia (east to China and south to Pakistan and India), central and eastern Europe, and north Africa (Callaghan 1999, Vinicombe 2000). The wintering range overlaps with the breeding range and extends to the Middle East, north-east and West Africa and South-East Asia. The current global population is estimated to fall in the band of c.180,000-240,000 individuals.
About 600 pairs breed in the El Kala National Park, Algeria (Vinicombe 2000), and there have been reports of breeding in Aswan, Egypt (Hoek et al. 2010). In Europe the breeding population is estimated at 17,400-30,100 pairs with the largest population in Romania (11,761-18,018 breeding pairs, concentrated in the Danube Delta) (O. Hatzofe in litt. 2005, BirdLife International 2015, N. Petkov in litt. 2015). Significant populations (between 1,000 and 5,000 pairs) are also found in Croatia and Azerbaijan, whilst smaller populations (c.500-1,000 pairs) are found in Russia, Hungary, Serbia and possibly Ukraine and Turkey (O. Hatzofe in litt. 2005, Dordevic et al. 2009, BirdLife International 2015). Populations in most European countries are showing signs of continuing large-scale declines. Sporadic breeding and/or wintering occurs in several western European countries.
In Asia, surveys have found high numbers, perhaps into the tens of thousands, in Inner Mongolia, China (Xing Lianlian pers. comm. 1998, although the accuracy of these counts is unclear, and may refer to non-breeding birds from other areas); 6,000-7,000 breeding pairs in Kazakhstan (S. Yerokhov verbally per N. Petkov in litt. 2005); and it is apparently common on the Tibetan Plateau, China (Scott 1993), and in winter in India, Bangladesh (70,000 birds counted at one group of four sites, R. Halder in litt. 2002), Myanmar and Thailand. In China it is considered to be expanding eastwards and increasing, with estimates of the breeding population of 1,500-2,000 pairs, and 6,000-8,000 wintering individuals (Zhao and Maming 2014).
Other large winter counts have been made in Azerbaijan (9,000 birds), Turkmenistan (21,000 birds) (Carboneras 1992) and Uzbekistan (7,000 birds [Kashkarov and Mukhina 1997], but recently less [S. Yerokhov verbally per N. Petkov in litt. 2005]). Small numbers occur on passage in Lebanon and Qatar and also in winter in Iraq, Israel, Jordan, Oman, Saudi Arabia, Syria, United Arab Emirates and Yemen.
The species declined markedly in Europe where there have been declines of more than 20% in nine European countries (BirdLife International 2004, O. Hatzofe in litt. 2005, BirdLife International 2015). Following a large decline in Europe during 1970-1990 (unpublished expert communications to S. Sklyarenko 2005), the species continued to decline during 1990-2000, when up to 45% of birds appear to have been lost (particularly in south-east Europe). The European population was believed to have declined overall by >30% (BirdLife International 2004, O. Hatzofe in litt. 2005). The most recent assessment of the European population size trend was assessed as unknown (BirdLife International 2015).
There is some evidence for declines in the number of birds in India (T. Katzner in litt. 2005, A. W. Tordoff in litt. 2005), Kazakhstan (Berezovikov and Samusev 1998, S. Subramanya in litt. 2006) (although other evidence suggests that this population is actually stable [S. Yerokhov verbally per N. Petkov in litt. 2005]), Kyrgyzstan (C. Inskipp in litt. 2005), Pakistan (N. Petkov in litt. 2005), Uzbekistan (Kashkarov and Mukhina 1997, S. Subramanya in litt. 2006) (but this population may have now stabilised [S. Yerokhov verbally per N. Petkov in litt. 2005]) and Viet Nam (Tucker and Heath 1994), and to a minor degree in Nepal (C. Inskipp in litt. 2005) (but possibly stable there [H. S. Baral in litt. 2005]). In Bangladesh wintering numbers have undergone moderately rapid declines and the species is classified as nationally Near Threatened (S. U. Chowdhury in litt. 2017). Winter counts from Israel suggest that the population has been generally stable in recent years (T. Heinicke in litt. 2005). In Ukraine, numbers fell from an estimated 65,000 in the late 1960s (Vinicombe 2000) to an estimated 300-600 pairs, whilst declines have also been recorded in Moldova, Belarus, Croatia, Greece, Latvia, Lithuania, Montenegro, Poland, Russia, Slovakia and Turkey (Vinicombe 2000, BirdLife International 2015). The Albanian population declined from 100-300 pairs to 0-3 pairs (N. Petkov in litt. 2003) and is now estimated at 5-30 pairs (BirdLife International 2015). However, populations remain stable in a number of other countries and slight local increases may have occurred in parts of Russia and Ukraine since hunting has diminished due to the speciess rarity (Vinicombe 2000). This speciess range has fluctuated considerably over the last c.150 years, although the overall trend has been towards a declining population and distribution. It is currently listed as Least Concern in Europe as the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (30% decline over ten years or three generations) (BirdLife International 2015).
DESCRIPTION
The most recent population estimates as collated by Wetlands International are as follows: 5,700-6,300 individuals in the western Mediterranean and in North and West Africa; 50,000-82,000 individuals in Eastern Europe and the eastern Mediterranean and Sahelian Africa; 25,000-50,000 individuals in western and south-west Asia as well as in north-east Africa, and 100,000 individuals elsewhere in Asia (Wetlands International 2017a,b; Mundkur et al. 2017), giving a total of c.180,000–240,000 individuals.
Trend Justification: This speciess range has fluctuated considerably over the last c.150 years as it has modified its distribution. However, most figures suggest widespread declines (Wetlands International 2016). Owing to significant local declines it was classified as Vulnerable in Europe, however the most recent assessment of the European population listed the trend as unknown and the speciess status as Least Concern (BirdLife International 2015). Evidence of declines in the larger Asian populations is sparse, and sometimes contradictory. In the absence of a clearer overall picture, the overall population is precautionarily suspected to be declining at a moderate rate over three generations.
HABITAT AND ECOLOGY
Behaviour This species is chiefly migratory, although little is known about its migratory routes and some individuals in southern populations may remain on the breeding grounds all year (del Hoyo et al. 1992, Scott and Rose 1996, Kear 2005). The species breeds from April or May until late June in single pairs or loose groups (Madge and Burn 1988, del Hoyo et al. 1992). Adults undertake a wing moulting period on the breeding grounds between July and August when large flocks of moulting individuals may gather (no moult migration is recorded however) (Scott and Rose 1996, Robinson and Hughes 2006). Departure from the breeding grounds begins in mid- to late-August and peaks in October, with the species arriving in wintering areas from late October (Scott and Rose 1996, Kear 2005, N. Petkov in litt. 2008). The return migration to the breeding grounds begins in early March (Scott and Rose 1996). Large gatherings of up to 100 individuals may occur prior to migration at the end of the post-breeding moult (July to August), and on migration the species often remains in small groups of 20-50 individuals (Madge and Burn 1988, Scott and Rose 1996, N. Petkov in litt. 2008). Outside of the breeding season, the species may be observed solitarily, in pairs or small loose groups of 2-5 individuals, and larger gatherings of 1,000-2,000 individuals are also recorded from wintering grounds in Niger and Chad (Madge and Burn 1988, Snow and Perrins 1998, Petkov et al. 2003).
Habitat The species shows a strong preference for fresh standing water and is very rarely found on flowing streams or rivers (Snow and Perrins 1998, N. Petkov in litt. 2008). It requires shallow water 30-100 cm deep close to littoral vegetation for feeding and generally avoids large open areas (del Hoyo et al. 1992, Scott and Rose 1996, Kear 2005). In Bulgaria there is evidence that the species shows a preference for well-vegetated, comparatively shallow wetlands with well-structured mosaic vegetation and a diversity of microhabitats. It is also found on shallow mudflats, possibly as a result of more accessible and abundant invertebrate food sources in this habitat (Petkov in prep.)
Breeding Shallow eutrophic freshwater pools and marshes with dense abundant submergent, floating, emergent and shoreline vegetation (e.g. reedbeds) are the major breeding habitats (del Hoyo et al. 1992, Kear 2005, N. Petkov in litt. 2008). Shallow banks with flooded vegetation and mudflats are particularly used for foraging during this season. The species shows a particular preference for breeding, moulting and staging on large river deltas and extensively managed fish ponds in Eastern Europe (Scott and Rose 1996, Kear 2005, Petkov 2006, Robinson and Hughes 2006). It is also less-commonly known to utilise brackish waters of estuaries, coastal lagoons, reservoirs, salt-pans, sewage farms, canals and drainage ditches during this season (Snow and Perrins 1998, Robinson and Hughes 2006, N. Petkov in litt. 2008).
Non-breeding Its habitat requirements outside of the breeding season are similar to those of the breeding season, although it may also frequent large lakes, open lagoons, coastal marshes with reedbeds and shallow coastal bays, straits and estuaries (del Hoyo et al. 1992, Scott and Rose 1996, Kear 2005, Robinson and Hughes 2006).
Diet Although the species is omnivorous, plant material such as seeds, roots and vegetative parts of aquatic plants (Potamogeton spp., Ceratophyllum spp., Scirpus spp., Carex spp. and macroalgae Chara spp.) dominates its diet (del Hoyo et al. 1992, Kear 2005). Animal matter taken includes worms, molluscs (snails), crustaceans, adult and larval insects (beetles, chironomids, dragonflies, waterbugs, caddisflies, flies), amphibians (frogs, tadpoles and spawn) and small fish up to 3 cm long (Brown et al. 1982, del Hoyo et al. 1992, Kear 2005).
Breeding site The nest is a low platform of reeds and other vegetation placed on the ground or on an islet or hummock in thick vegetation close to water (Johnsgard 1978, del Hoyo et al. 1992, Snow and Perrins 1998, Kear 2005). Alternatively, nests may be placed over water on floating mats of vegetation or in dense reedbeds along the shoreline (Johnsgard 1978, Kear 2005). Breeding success was found to be higher if the nest was located over deeper water and near tall vegetation (Djelailia et al. 2018).
THREATS
The species is threatened by the degradation and destruction of well-vegetated shallow pools and other wetland habitats (e.g. changes to the vegetation community, disruption of water regimes, siltation, and increased water turbidity) as a result of excessive drainage and water abstraction, peat extraction, eutrophication (from inadequate sewage treatment and nutrient run-off), oil pollution, dam and barrage construction, the building of infrastructure on flood-plains and river canalisation (del Hoyo et al. 1992, Vinicombe 2000, Kear 2005, Grishanov 2006, Robinson and Hughes 2006). Changing land management practices such as reed cutting and burning during the breeding season, over-grazing, decreased grazing and mowing of wet meadows, and abandonment (causing succession to scrub) or intensification (causing reversion to open water) of extensively managed fishponds also threatens the species (Vinicombe 2000, Kear 2005, Petkov 2006, Robinson and Hughes 2006). The introduction of non-native species has caused further habitat degradation. For example, the stocking of lakes with and accidental introduction of Grass Carp Ctenopharyngodon idella has resulted in reductions in macrophyte biomass and corresponding reductions in invertebrate biomass (Kear 2005, Robinson and Hughes 2006), and in Bulgaria an introduced shrub (Desert False Indigo Amorpha fruticosa) is changing the ecological character of wetlands (Robinson and Hughes 2006). Introduced predators such as the Wels Catfish Silurus glanis (Kazakhstan) that predate ducklings, and the Muskrat Ondatra zibethicus (Aral Sea region) have also caused population declines (Robinson and Hughes 2006). Increased drought due to global climate change may pose a threat to the species in part of its range (Vinicombe 2000, Robinson and Hughes 2006). Disturbance by fishing boats and anglers alongside fringe vegetation could cause abandonment of the breeding sites or disrupt the timing of breeding (N. Petkov in litt. 2008). Hunting is another serious threat to the species (Vinicombe 2000, del Hoyo et al. 1992, Robinson and Hughes 2006). Large numbers are shot on passage in the autumn (e.g. through the Volga delta) and on the wintering grounds (e.g. Sudan) (Kear 2005, Balmaki and Barati 2006). Illegal and accidental hunting also persists in most European countries (Brochet et al. 2018). Other lower-level threats include lead poisoning (from ingestion of discarded lead shot), fires in areas of reed thickets, peat bogs and woods, entanglement and drowning in fishing nets and hybridisation with native species (e.g. Tufted Duck Aythya fuligula and Common Pochard Aythya ferina) (Grishanov 2006, Robinson and Hughes 2006, Leuzinger 2010).
USE AND TRADE
Large numbers are shot on passage in the autumn (e.g. through the Volga delta) and on the wintering grounds (e.g. Sudan) (Kear 2005, Balmaki and Barati 2006). Illegal and accidental hunting also persists in most European countries (Brochet et al. 2018). It frequently occurs in captive wildfowl collections.
CONSERVATION ACTIONS
Conservation and research actions underway
The species is fully protected in Belarus, Bulgaria, Czech Republic, France, Germany, Hungary, Italy, Moldova, Netherlands, Russia, Slovakia, Slovenia, Spain and Switzerland, and is protected from hunting in Austria, Belgium, Greece, Poland, Turkey and Ukraine. It is listed on Annex I of the European Union Directive on the Conservation of Wild Birds, on Appendix III of the Bern Convention and on Appendices I and II of the Bonn Convention. The species has received little international conservation action, although a number of national initiatives have been developed recently, notably habitat management in Bulgaria and re-introduction schemes in Italy (Berezovikov and Samusev 1998). One of the highest priorities for this species is to establish systematic annual monitoring of Asian populations to more accurately assess trends. Such monitoring, if it provided evidence of continuing and significant declines across major Asian populations, could provide reason to uplist this species. An International Single Species Action Plan has been adopted by the Bern Convention, CMS and AEWA, which lays out a framework for conservation action throughout the species range (Robinson and Callaghan 2003). A restoration project for two key breeding sites on the Danube in Bulgaria is underway, funded by the World Bank (N. Petkov in litt. 2003).
Conservation and research actions proposed
Promote the full legal protection of the species and its habitat through national and international legislation, promote environmentally friendly management of fishponds in Eastern Europe, promote adequate protection and management of key sites, promote conservation in the wider environment for the benefit of the species and its habitat, prevent mortality and disturbance caused by hunting, monitor the remaining population (particularly in Asia) and develop census techniques, investigate productivity and mortality, investigate ecology and limiting factors, investigate the impact of C. idella on the species and its habitat; develop and implement education programmes for the conservation of the species and its habitats. |
