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 decreasing but the rate of decline is not thought to 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.160,000-1,200,000 individuals (Wetlands International 2015), while national population sizes have been estimated at c.1,000-10,000 individuals on migration and < c.50 wintering individuals in Taiwan and c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Russia (Brazil 2009). The European population is estimated at 15,500-50,700 pairs, which equates to 30,900-101,000 mature individuals (BirdLife International 2015).
The overall population trend is declining. Some populations have unknown trends or are stable (Wetlands International 2015). The European population is estimated to be decreasing by less than 25% in 19.2 years (three generations) (BirdLife International 2015).
Behaviour This species is a full migrant (del Hoyo et al. 1996). The East Asian population migrates along the eastern coast of the continent, whereas the populations in western Asia pass south overland through the Caspian region, the Middle East (del Hoyo et al. 1996) or between the Ural and Volga rivers (Snow and Perrins 1998). The Finnish population flies across Eastern Europe and crosses the Mediterranean and Sahara non-stop (del Hoyo et al. 1996). Breeding occurs between May and June (del Hoyo et al. 1996), after which the adults depart in early-July (the juveniles departing mainly in August) (Snow and Perrins 1998), to arrive in their wintering grounds between August and October (Urban et al. 1986). The return movement northward from Africa begins in late-March and continues throughout April (Snow and Perrins 1998). Many one-year-old (Urban et al. 1986) and other non-breeding birds remain in the wintering grounds throughout the northern summer (del Hoyo et al. 1996). This species is known to breed semi-collonially (del Hoyo et al. 1996) (as many as 10 nests have been found within a square kilometer) (Johnsgard 1981), but is mainly solitary outside of the breeding season (Snow and Perrins 1998). Occasionally it occurs in small flocks of 5-25 individuals (del Hoyo et al. 1996), or up to 300 at tidal roosting sites (Urban et al. 1986). The species is both a diurnal and nocturnal forager, but its nocturnal activities may by restricted to moonlit nights (Rohweder and Baverstock 1996). Habitat Breeding This species breeds in lowland valleys in northern boreal forest and tundra, especially on floodplains with flooded meadows and marshes, and where overgrown moist grasslands alternate with willow scrub (del Hoyo et al. 1996, Snow and Perrins 1998). It also frequents lakesides and marshy banks of streams, and extends to the coasts of sheltered seas in the Baltic (Snow and Perrins 1998). The species avoids mountains, fast rocky streams, steep or broken terrain, extensive open spaces and tall dense forest (Snow and Perrins 1998). Non-breeding Outside of the breeding season the species inhabits tropical coasts, especially open intertidal estuaries and mudflats, as well as coral reefs, sandy and pebbly beaches, sandbars and mudlfats at river mouths, coastal swamps, saltpans (del Hoyo et al. 1996), coastal lagoons and saltmarsh creeks (Johnsgard 1981). It can occasionally also be found up to 10 km inland around brackish pools and riverbeds, and often forms communal roosts in the branches of mangroves (del Hoyo et al. 1996). During migration the species may stop-over at inland freshwater wetlands (del Hoyo et al. 1996), such as muddy lakes or river edges (Urban et al. 1986). Diet Breeding On its breeding grounds the diet of this species consists mainly of adult and larval midges (Diptera) as well as seeds (del Hoyo et al. 1996). Non-breeding In its wintering grounds and on migration the diet of this species is more varied, consisting of a variety of insects, small molluscs, crustaceans (including crabs), spiders and annelid worms (del Hoyo et al. 1996). Breeding site The nest is a shallow depression close to water either in the open, or sheltered by short grasses (Urban et al. 1986).
In China and South Korea important migrational staging areas of this species around the coast of the Yellow Sea are being lost through land reclamation, and degraded as a result of declining river flows (from water abstraction), increased pollution, unsustainable harvesting of benthic fauna and a reduction in the amount of sediment being carried into the area by the Yellow and Yangtze Rivers (Barter 2002, Barter 2006). This species is also potentially at risk from exposure to DDT's in southern India (Tanabe et al. 1998). Within its European range, the breeding success of this species is not well known, but there are indications that an overall increase of common gulls, crows and mammalian predators has led to increased nest predation. Anthropogenic habitats in the wood processing industry are subject to unpredictable changes that can drive small range populations to extinction within a short period of time. Historically there are indications of illegal egg collection at the European breeding sites (HELCOM 2012).
Conservation Actions Underway
The following information refers to the species's European range only: Bern Convention Appendix II. EU Birds Directive Annex I. CMS Appendix II. There are no known current conservation measures for this species.
Conservation Actions Proposed
The following information refers to the species's European range only: Research into population and migratory movements should be started in order to reveal the wintering sites. More efforts are needed to locate all breeding sites in the Bothnian Bay. At anthropogenic breeding sites, authorities should be aware of the presence of the species and its legal status (HELCOM 2012).
Text account compilers
Ekstrom, J., Ashpole, J, Butchart, S., Malpas, L.
BirdLife International (2019) Species factsheet: Xenus cinereus. Downloaded from http://www.birdlife.org on 12/12/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 12/12/2019.