Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The global population is estimated to number c.190,000-380,000 individuals (Wetlands International 2015), the population in Russia is estimated at c.10,000-100,000 breeding pairs and c.1,000-10,000 wintering individuals (Brazil 2009). The European population is estimated at 4,000-7,000 pairs, which equates to 8,000-14,000 mature individuals (BirdLife International 2015).
The overall population trend is increasing, although some populations may be stable and others have unknown trends (Delany and Scott 2006). This species has undergone a small or statistically insignificant increase over the last 40 years in North America (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). The population trend in Europe is unknown (BirdLife International 2015).
The Harlequin Duck is found in north-western and north-eastern North America, eastern Russia, the Aleutian Islands, southern Greenland and Iceland. It can winter further south, being found off Korea, northern California and North Carolina (U.S.A.) (del Hoyo et al. 1992).
This species is found breeding on swift torrents and rapid streams of rugged uplands, normally wintering on rocky coastlines. It feeds mainly on insects and their larvae in summer, catching molluscs and crustaceans in winter. Feeding mostly occurs by diving, but also dabbling and head-dipping in shallow water. Breeding begins in May or June, nesting on the ground concealed in vegetation (del Hoyo et al. 1992).
Wintering areas are highly clustered, and the species demonstrates very high site fidelity (95% of radio-tracked females remained in the same region in which they were tagged [Iveson and Esler 2006]), which makes the species vulnerable to the impacts from large oil spills. Number of wintering birds were 25% lower in oiled areas following the Exxon Valdez spill, and still showed reduced survival rates 11-14 years after the incident, suggesting chronic oil contamination. Full recovery after the catastrophic Exxon Valdez spill was estimated to take 24 years (Iveson and Esler 2010). The species is threatened by the development of hydroelectric schemes which result in the diversion and siltation of rivers (Tucker and Heath 1994, Carboneras and Kirwan 2013). Damming is affecting populations in Europe, Newfoundland and to a lesser extent, the West coast of North America. One colony has already been lost due to diversion of the river Thorisos, following the installation of a hydroelectric dam. Hunting occurs at low levels throughout the species’ range, with small bag limits in most areas (e.g. 134 annually in western Washington between 2004-2014), and although more than 1,000 are taken annually in Alaska (Sea Duck Joint Venture 2015), the annual level of subsistence harvest is estimated at an additional 2,080 birds (Rothe et al. 2015). The large-scale introduction of Atlantic Salmon (Salmo samar) and Brown Trout (Salmo trutta) can result in competition for blackfly larvae and pupae, the duck's main food source. In the 1930s American Mink (Mustela vison) were introduced to the European range and may have reduced breeding success although the impact has not been quantified (Tucker and Heath 1994). Dredging for minerals in Lake Mývatn may affect algal blooms which form another important food source (Tucker and Heath 1994).
Conservation Actions Underway
CMS Appendix II. Bern Convention Appendix II. The following information refers to the species's European range only: The species is protected against hunting and egg-collecting in Iceland. The core area, River Laxá, is partly protected by law, is an Important Bird Area (IBA) and a Ramsar Site (Tucker and Heath 1994).
Conservation Actions Proposed
The following information refers to the species's European range only: The identification of other rivers with high numbers of breeding pairs is needed and these should be protected from development. A study of the effect of the American Mink on the species should be undertaken (Tucker and Heath 1994). Research should also be undertaken on resource use on the coast, individual females and the survival of small young and the relationship between breeding, moulting and wintering sites (Gardarsson 2008).
Text account compilers
Bennett, S., Calvert, R., Ekstrom, J., Butchart, S., Fjagesund, T., Hermes, C., Martin, R., Stuart, A.
BirdLife International (2020) Species factsheet: Histrionicus histrionicus. Downloaded from http://www.birdlife.org on 23/10/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/10/2020.