Justification of Red List Category
This species is suspected to have undergone a population reduction over the past three generations that approaches the threshold for listing as Threatened. The recent decline may be part of a longer-term fluctuation and the population should be monitored carefully to ascertain whether it shows signs of stabilising.
The global population is estimated to number c. 925,000-1,030,000 individuals, based on expert opinion (Wetlands International 2019), and comprising the three separate subspecies of H. o. ostralegus (820,000), H. o. longpipes (100,000-200,000) and H. o. osculans (5,000-10,000; Wetlands International 2019). This is roughly equivalent to 616,667-686,667 mature individuals, here placed in the band 500,000-999,999 mature individuals. Population estimates are lower than those of recent assessments due to the recent taxonomic split, whereby Haematopus finschi (South Island Oystercatcher), previously considered a subspecies of Haematopus ostralegus (del Hoyo et. al. 2014), was designated a separate species.
The overall population trend is decreasing (Wetlands International 2019, Nagy et al. 2014, van de Pol et al. 2014, van Roomen et al. 2014a, BirdLife International 2015). The population of ostralegus, the largest of the three subspecies, increased strongly between the 1960s and the 1990s (van de Pol et al. 2014), but has subsequently declined significantly, at a rate exceeding 40% over three generations. The long-term increases are often ascribed to successful adaptation to breeding inland on newly available agricultural grasslands (Meltofte 1993, Goss-Custard et al. 1996) however, apparent concurrent increases in coastal populations contrast with this view. The longipes population is reported to be stable (Sarychev and Mischenko 2014, van Roomen et al. 2014b) and the trend for the osculans population is unknown (Melville et al. 2014). Recent rapid declines in the H. o. ostralegus population may however be part of a longer-term fluctuation. Mechanical shellfisheries operations have been severely restricted in the Netherlands (van de Pol et al. 2014), however, there has not been a concomitant halt in the population decline despite food stocks recovering (M. van de Pol in litt. 2016). Further information is needed to confirm whether the population may reach stability in the future or if it will continue to decline. Because of this uncertainty, the overall rate of decline is currently placed in the band 20-29% in three generations although the current rate within the largest population appears to be higher.
The species has a wide range comprising three flyway populations. H. o. ostralegus breeds from Iceland and Scandinavia east to north-west Russia, south through U.K. to north-west France, with isolated populations in the Mediterranean, and winters on coasts south to West Africa. H. o. longipes breeds from west and central Russia south to the Black, Caspian and Aral Seas, and east to western Siberia, and winters on coasts from East Africa through Arabia to India; H. o. osculans breeds from coastal north-east Russia through Manchuria to the west and south coasts of the Korean Peninsula south to Fujian province, China, and winters in eastern China and along the west coast of the Korean Peninsula (more than 50% of the population is thought to winter at just one site, Yubu Island, South Korea and a further 25% are thought to winter at Lianyunggang, Jiangsu, China; Melville et al. 2014).
The species breeds on coastal saltmarshes, sand and shingle beaches, dunes, cliff-tops with short grass and occasionally rocky shores, as well as inland along the shores of lakes, reservoirs and rivers or on agricultural grass and cereal fields, often some distance from water (Hayman et al. 1986, del Hoyo et al. 1996). Outside of the breeding season the species is chiefly coastal, frequenting estuarine mudflats, saltmarshes and sandy and rocky shores (del Hoyo et al. 1996). The nest is a shallow scrape on the ground often on raised surfaces (e.g. earth banks) in the open or in short vegetation on cultivated or uncultivated land, cliff-tops, rocky outcrops or clearings in taller vegetation including woods and moorland (Hayman et al. 1986, del Hoyo et al. 1996, Snow & Perrins 1998).
Most populations of this species are fully migratory, inland breeders moving to the coast for the winter (del Hoyo et al. 1996). The species breeds from April to July (Hayman et al. 1986) in solitary pairs or small groups (Flint et al. 1984), during the winter foraging singly or in small groups of up to 10 individuals (Snow & Perrins 1998) and with larger flocks often forming in major bays and estuaries and at roosting sites (Hayman et al. 1986, del Hoyo et al. 1996, Snow & Perrins 1998). When foraging on soft intertidal substrates bivalves and gastropods are the most important food items for this species (del Hoyo et al. 1996). Polychaetes and crustaceans are more important in estuaries however, and molluscs (e.g. mussels, limpets and whelks) are most important on rocky shores (del Hoyo et al. 1996). When inland, prey such as earthworms and insect larvae (e.g. caterpillars and cranefly larvae) are also taken (del Hoyo et al. 1996).
The main threat to the species is the over-fishing of benthic shellfish and the resulting disappearance of intertidal mussel and cockle beds (Atkinson et al. 2003, Verhulst et al. 2004, Ens 2006, van de Pol et al. 2014). Bait digging has also been identified as a threat through loss of prey species and disturbance to the benthic fauna (van de Pol et al. 2014). The species is also threatened by habitat degradation on its wintering grounds due to land reclamation (for example in the Yellow Sea [Melville et al. 2014]), pollution, human disturbance (Kelin & Qiang 2006) (e.g. from construction work or recreational activities [Burton et al. 2002, van de Pol et al. 2014]), coastal barrage construction (Burton 2006), industrial development including development of ports and oil extraction, oil spills, wind farms (Melville et al. 2014) and reduced river flows (Kelin & Qiang 2006). Rapid and extensive land reclamation is reported from staging and wintering grounds for the osculans population in South Korea and China and large-scale planting of Spartina alterniflora on the coast of eastern China may cause loss of foraging and nesting habitats (Melville et al. 2014). Intensive agriculture including frequent mowing of grasslands and high densities of grazing livestock threatens chicks, eggs and nests and high levels of fertilizers and pesticides can reduce soil invertebrate biomass (van de Pol et al. 2014). A reduction in eutrophication is likely to have contributed to declines in some areas, owing to a loss of food resources (van de Pol et al. 2014, H. Meltofte in litt. 2015).
Sea level rise leading to increased coastal erosion and flooding is contributing to habitat loss in some areas (Melville et al. 2014, van de Pol et al. 2014). Climate change has advanced the average egg-laying date of the species and is likely to reduce recruitment of bivalves, however warmer winters are expected to benefit the species leading to lower winter mortality (van de Pol et al. 2014). Droughts in some inland areas are likely to lead to a loss of suitable habitat (Melville et al. 2014, Sarychev & Mischenko 2014).
The species is hunted in France but the effects of hunting at the population level are not known (van de Pol et al. 2014). It may be subject to subsistence egg collection in China (Melville et al, 2014) and illegal hunting elsewhere (Sarychev & Mischenko 2014). Eggs and chicks are known to be predated by Corvidae, gulls, American Mink Neovison vison, dogs and foxes Vulpes vulpes (Sarychev & Mischenko 2014). The invasive Pacific Oyster Crassostrea gigas has become abundant in the Oosterschelde (Netherlands) and is increasing in the Dutch Wadden Sea (van de Pol et al. 2014). Eurasian Oystercatcher generally does not eat this species of oyster which is reported to be invading mussel beds and may compete with cockles and mussels thus reducing food availability. However Pacific Oyster beds could also provide an area for mussel beds to re-establish. The species is susceptible to avian influenza so may be threatened by future outbreaks of the virus (Melville & Shortridge 2006).
In the northern part of the longipes population breeding range, cessation of grazing in coastal areas leading to development of shrubby vegetation threatens breeding habitats (Sarychev and Mischenko 2014). Conversely, intensive grazing in some areas may pose a threat to this population. Pollution from sewage, heavy metals and organochlorine pesticides have been identified as potential threats for the osculans population (Melville et al. 2014).
Conservation and Research Actions Underway
The species is listed on Annex II (B) of the EU Birds Directive. Mechanical shellfisheries operations have been severely restricted in the Netherlands (van de Pol et al. 2014).
Conservation and Research Actions Proposed
Shellfish fishing at wintering and stop-over habitats needs to be sustainably managed. Ensure key habitat for the species is protected, including implementation of international agreements and ensure legislation protecting the species is enforced. Removing large numbers of gulls (e.g. Larus argentatus and Larus fuscus) from islands may attract higher breeding numbers of the species but may not improve the overall breeding conditions (Harris & Wanless 1997). There is also evidence that the creation of large marine protected areas (MPAs) to protect this species from the threat of anthropogenic shellfish over-fishing may not be an effective management or conservation technique on a global scale, especially if over-fishing continues to occur in adjacent areas (Verhulst et al. 2004). Limit human activities in some areas to prevent disturbance (van de Pol et al. 2014). Limit hunting in France when cold weather pushes large numbers of birds into France (van de Pol et al. 2014). Increase awareness of the species. Support traditional farming methods that benefit the species in the range of the longipes population (Sarychev & Mischenko 2014).
Monitor populations at wintering and breeding areas throughout its range, and record breeding success. Introduce frequent standardised surveys, particularly in the Nordic countries (van de Pol et al. 2014). Research breeding distribution of the osculans population, conduct ringing studies to understand migratory patterns and investigate why Yubu Island in South Korea and southern Shandong/northern Jiangsu in China are key sites for the species (Melville et al, 2014). Identify stopover sites and wintering areas for the longipes population (Sarychev & Mischenko 2014). Assess impacts of land reclamation on the species in South Korea and China (Melville et al. 2014). Further research is needed to investigate the cause of declines in areas such as Germany and Denmark, to model the potential effects of climate change on the species, assess the impact of human disturbance and to look at population dynamics (van de Pol et al. 2014).
Nominate ostralegus 40-47.5 cm. Breeding adult has black head, neck, upper breast, scapulars, upperwing coverts and tail (Hockey et al. 2013). White middle and lower back, rump, uppertail coverts, lower breast and belly. Broad white wingbar from inner secondaries to middle primaries. Red eye and eye-ring. Bill orange-red. Legs pink. Bill length of Palearctic races increases from west to east: ostralegus (male 76 mm, female 81 mm); longipes (male 78 mm, female 89 mm); osculans (male 99 mm, female 96 mm) (Hockey et al. 2013). Female slightly larger than male with longer, thinner bill. Juvenile resembles adult. Races mainly differ on bill length, and extent of white wingbar. Similar species Pied Oystercatcher H. longirostris has narrower white wingbar which does not extend onto primaries. American Oystercatcher H. palliatus has yellow eye and blackish brown dorsal colouration. Magellanic Oystercatcher H. leucopodus has yellow eye and almost wholly white secondaries. Voice Most commonly heard call a repeated over-slurred piping whistle, "peep" or "kleep". Also makes piping whistles in display.
Text account compilers
Pople, R., Van den Bossche, W, Wheatley, H., Ieronymidou, C., Everest, J., Ashpole, J, Wright, L, Burfield, I., Malpas, L., Ekstrom, J., Butchart, S., Symes, A., Taylor, J.
Meltofte, H. & van de Pol, M.
BirdLife International (2020) Species factsheet: Haematopus ostralegus. Downloaded from http://www.birdlife.org on 28/11/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 28/11/2020.