The snowy plover (Anarhynchus nivosus, formerly Charadrius nivosus) is a small shorebird found in the Americas. It is a member of the bird family Charadriidae, which includes the plovers, dotterels, and lapwings. The snowy plover was originally described by John Cassin in 1858, but was classified as a subspecies of the Kentish plover in 1922. Since 2011, the snowy plover has been recognized as a distinct species based on genetic and anatomical differences from the Kentish plover. Two or three subspecies are recognized, distributed along the Pacific coast of North America, Ecuador, Peru, and Chile, in several inland areas of the US and Mexico, along the Gulf Coast, and on Caribbean islands. The coastal populations consist of both residential and migratory birds, whereas the inland populations are mostly migratory. It is one of the best studied endemic shorebirds of the Americas, and one of the rarest. Snowy plovers are pale brown above and white below, with a white band on the hind neck. During the breeding season, males have black patches behind the eye and on the side of the neck; the neck patches are separated from each other and do not form a continuous breast band as in many other plovers. Snowy plovers can also be distinguished from other plovers in having an all-black and slender bill, and gray to black legs. The typical call is a repeated "tu-wheet". This plover inhabits open areas in which vegetation is absent or sparse, in particular coastal sand beaches and shores of salt or soda lakes, where it feeds on invertebrates such as crustaceans, worms, beetles, and flies. At the beginning of the breeding season, males excavate multiple nest scrapes that are advertised to females; one of these scrapes is later selected for breeding. Some females will desert their brood soon after the chicks hatch to re-mate with another male, while their first mate will continue to rear the chicks. Such polygamy is uncommon in birds, and is possibly a strategy to maximize breeding success. There are more males than females – 1.4 times as many in California – and the more pronounced this sex ratio imbalance is, the more females engage in polyandrous behavior. The snowy plover is listed as near threatened by the International Union for Conservation of Nature. The main threats are habitat destruction due to invasive beach grasses, urban development, as well as frequent disturbance due to recreational uses of beaches. Conservation measures on the US Pacific coast include roping-off beach areas that are used for breeding, the removal of invasive beach grasses, and protection against egg predators. While such measures have been successful locally, the global population is thought to be in decline.
Taxonomy and systematics The snowy plover was first described by John Cassin in 1858 as Aegialitis nivosa, based on a skin collected in 1854 by William P. Trowbridge in Presidio, which later became part of San Francisco. This skin, the holotype of the species, was subsequently lost. Although originally part of the collection of the National Museum of Natural History, it was given to the collector Henry E. Dresser of England in 1872. In 1898, the Dresser collection was transferred to the Victoria University of Manchester, but the skin was apparently not part of this transfer. Joseph Grinnell, who attempted to locate the holotype in 1931, suggested that Dresser may have been unaware of the specimen's significance and may have given it elsewhere. The snowy plover is one of the best-studied endemic shorebirds of the Americas, although most of this research was carried out on western North American populations, with few monitoring programs targeting the South American and eastern North American populations. Plovers (Charadriinae) are a subfamily of small shorebirds that breed in open habitats on all continents except Antarctica. Together with the lapwings (Vanellinae), they form the family Charadriidae. The snowy plover was traditionally considered to be a species within the genus Charadrius, which comprised 32 extant species and was therefore the most species-rich genus of the family. However, a 2013 genetic analysis found that the lapwings are nested within Charadrius; the latter is therefore polyphyletic (is not a natural group, i.e., the most distantly related Charadrius species are more closely related to lapwings than to each other). Some subsequent studies confirmed this and proposed to split Charadrius into five separate genera. The snowy plover, formerly Charadrius nivosus, was transferred into the genus Anarhynchus, as Anarhynchus nivosus, along with 22 other plover species; in 2023, this transfer was recognized by the International Ornithologists' Union. Before the transfer, Anarhynchus contained only one species, the wrybill from New Zealand. The name Anarhynchus derives from the Ancient Greek ἀνα- (ana-) meaning 'backward' and ῥυγχος (rhunkhos) meaning 'bill'. The species name nivosus is Latin for 'snowy'. The snowy plover appears to be most closely related to the Kentish, the white fronted, the Malaysian, the chestnut-banded, and the red-capped plover, as shown in a cladogram from a 2015 study:
The snowy plover is closely related, and visually similar, to the Kentish plover of Eurasia and Africa. Harry C. Oberholser, in 1922, argued that the differences in plumage between these species are not consistent, and no clear line of demarcation could be drawn. Consequently, he classified the two subspecies of the snowy plover that were recognized at that time (nivosus and tenuirostris) as subspecies of the Kentish plover. This assessment was subsequently followed by most authors, until a 2009 genetic study re-established the snowy plover as a separate species. This study noted that, besides differences in the mitochondrial and nuclear DNA, snowy plovers differ from Kentish plovers in being smaller, having shorter tarsi and wings, different chick plumages, and different advertisement calls of the males. In 2011, the International Ornithological Congress (IOC) and the American Ornithologists' Union (AOU) recognized them as separate species.
Subspecies
Two to three subspecies are commonly recognized:
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