Justification of Red List Category
This plover seems to have declined rapidly in parts of its range, although the population may have remained stable in others. Overall a moderately rapid population decline is suspected, owing to the effects of habitat loss and degradation, and disturbance to nesting sites. The species is therefore listed as Near Threatened.
The North American population was estimated at 25,869 individuals by Thomas et al. (2012). C. n. occidentalis in western South America has been estimated to number 8,000-10,000 individuals, and there are c.2,500 individuals of the population sometimes separated as C. n. tenuirostris on the Gulf Coast, Bahamas and Caribbean (Wetlands International 2014), giving a tentative total of perhaps 36,000-38,000 individuals, roughly equating to 24,000-26,000 mature individuals. Partners in Flight (2019) however, estimate a larger population of 31,000 mature individuals hence, the population is placed here in the range 24,000-31,000 mature individuals.
Population trends for this species are difficult to quantify. Whilst some subpopulations are said to be declining (e.g. occidentalis, tenuirostris and nivosus on the Pacific coast [Page et al. 2020, Wetlands International 2020]), trends in other subpopulations are said to be stable or even increasing (Meehan et al. 2018, Page et al. 2020) or are largely unknown (Wetlands International 2020). Overall, the species is assumed to be undergoing a moderately rapid population decline approaching 30% over three generations (10.5 years), following evidence of regional declines and on-going threats such as habitat degradation and disturbance (Page et al. 2009, Thomas et al. 2012). Further evidence is required to confirm this trend however.
Charadrius nivosus is a widespread partial migrant in North America, Central America, western South America and the Caribbean, where it occupies coastal habitats and inland, usually saline waterbodies (del Hoyo et al. 1996). A recent study by Thomas et al. (2012) estimated the total North American population to be 25,869 breeding individuals, with approximately 42% of the breeding population in North America residing at two sites; Great Salt Lake, Utah, and Salt Plains National Wildlife Refuge, Oklahoma. Saalfeld et al. (2013) compared survey counts of adult C. nivosus between 1999-2000 and 2008-2009 on two lakes in the Southern High Plains of Texas that support a large proportion of the regional population, and showed that they decreased by 78% at one saline lake (from 80 adults/survey to 8 adults/survey), although they remained constant at another lake (from 45 adults/survey to 41 adults/survey). At a small breeding site in southern Colorado, USA, individuals during the breeding season declined from 141 adults to 37 adults between 2007 and 2015 (BLM, unpublished data).
The species chiefly occurs along sea coasts, but also open flats near brackish or saline lakes, lagoons, seasonal water courses, salt-works and depressions.
The species is threatened by the disturbance of coastal habitats (e.g. tourists trampling nests and disturbing roosts on beaches) (Lafferty et al. 2006). It is also threatened by the degradation and loss of wetland habitat through environmental pollution, land reclamation (del Hoyo et al. 1996, Barter 2006), urbanisation (del Hoyo et al. 1996) and a reduction in the amount of sediment being carried into coastal areas by rivers (Barter 2006). The species is susceptible to avian botulism, so may be threatened by future outbreaks of the disease (Blaker 1967). Water availability and allocation effects inland breeding sites, and may become more challenging with changes in climate (B. Andres in litt. 2016).
Conservation and research actions underway
Management information Shallowly flooding a previously dry habitat at Owens Lake, California, was found to attract more breeding pairs to the area and had the effect of extending the nesting season by c.1 month (Ruhlen et al. 2006). At Batiquitos Lagoon, California, creating new nesting areas from dredging spoils (e.g. coarse-grained sand and shell fragments) attracted more breeding pairs and non-breeding individuals, possibly because the new areas were covered with less debris and a smaller amount of tall vegetation than older sites (Powell and Collier 2000). In the Salt Plains National Wildlife Refuge, Oklahoma, there is evidence that nests adjacent to herbaceous and shrub vegetation suffer significantly lower losses to flooding but significantly higher losses to mammalian predation than those 500 or 1,000 m away (Urban et al. 1986, del Hoyo et al. 1996). In the same area artificial nest ridges (made by ploughing) and nest mounds constructed from existing materials (gravel, sand and clay) were found not to reduce nest flooding (Koenen et al. 1996a). Predator exclusion experiments from nesting areas using electric fences in the Salt Plains National Wildlife Refuge, Oklahoma (Koenen et al. 1996a) and in Monterey Bay, California were unsuccessful in increasing the number of chicks fledged per male (Neuman et al. 2004) or significantly reducing annual egg predation (this was probably still limited by avian predation) (Koenen et al. 1996a), although in Monterey Bay the hatching success of nests within the exclosure did increase (Neuman et al. 2004) and the overall nesting success was higher for breeding pairs within the Salt Plains National Wildlife Refuge exclosures (Koenen et al. 1996a). At Monterey Bay the predator exclosures were also not successful in increasing adult breeding numbers, and the mortality of incubating adults was actually higher within the enclosures than outside them (Neuman et al. 2004). In coastal Oregon, habitat management to remove invasive grasses and provide more suitable nesting substrate more than doubled nest survival whilst nest exclosures and predator management also increased nesting success in both Oregon and Washington also (Dinsmore et al. 2014, 2017); such changes were not correlated with changes in other population viability factors, such as fledging success however (Dinsmore et al. 2014). Furthermore, lethal predator removal and reduced human disturbance were shown to facilitate population recovery and alleviate the reliance upon immigration in a sink population in northern California, although nest exclosures were shown to reduce population growth due to their compromising impact on adult survival (Eberhart-Phillips and Colwell 2014). Pearson et al. (2016) have also noted both the benefits of nest exclosures on nesting success but also their negative influence on adult survival in populations in coastal Washington (2006-2012). Gaines et al. (2020) documented the increase in adult survival throughout Snowy Plovers in Oregon between 1990-2014 following the removal of nest exclosures and initiation of lethal predator removal. On beaches in Santa Barbara, California, erecting protective barriers to direct tourist foot-traffic away from sections of upper beach was found to decrease disturbance of the species by more than half and attracted increased numbers of breeding pairs, although the distribution of the species on the beach contracted to within the protected area (Lafferty et al. 2006).
Conservation and research actions proposed
Carry out systematic monitoring in breeding areas and wintering sites. Evaluate key threats. Continue predator exclusions and protective barriers to prevent disturbance at key nesting areas.
16.5cm. A small, pale plover of the Americas, previously included within C. alexandrinus. Round-headed and short-necked with a short slender black bill and dark patches on the breast side. All plumages show a white forecrown leading into a white supercillium, white throat and underparts and pale brown-grey upperparts. Legs are relatively short and pale grey. Breeding males show a trace of rufous on hindcrown, which is mostly grey brown and have black markings on mid-crown, ear coverts and as a patch on the breast sides. Females typically have these areas brown, though may show some black. Similar spp. C. alexandrinus is on average slightly darker, have slightly longer and darker legs and breeding males typically have more extensive black on the lores. Voice. A quiet 'ku-wee' and low 'knut'.
Text account compilers
Wheatley, H., Everest, J.
Andres, B.A., Barrio, J., Butchart, S., Ekstrom, J., Malpas, L., Symes, A., Taylor, J. & Wraithmell, J.
BirdLife International (2021) Species factsheet: Charadrius nivosus. Downloaded from http://www.birdlife.org on 16/09/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/09/2021.