Snowy Plover
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The snowy plover (''Anarhynchus nivosus'') is a small
shorebird 245px, A flock of Red_knot.html" ;"title="Dunlins and Red knot">Dunlins and Red knots Waders or shorebirds are birds of the order Charadriiformes commonly found wikt:wade#Etymology 1, wading along shorelines and mudflats in order to foraging, ...
found in the
Americas The Americas, sometimes collectively called America, are a landmass comprising the totality of North America and South America.''Webster's New World College Dictionary'', 2010 by Wiley Publishing, Inc., Cleveland, Ohio. When viewed as a sing ...
. It is a member of the bird family
Charadriidae The bird family Charadriidae includes the plovers, dotterels, and lapwings. The family contains 69 species that are divided into 10 genera. Taxonomy The family Charadriidae was introduced (as Charadriadæ) by the English zoologist William El ...
, which includes the
plover Plovers ( , ) are members of a widely distributed group of wader, wading birds of subfamily Charadriinae. The term "plover" applies to all the members of the subfamily, though only about half of them include it in their name. Species lis ...
s,
dotterel The Eurasian dotterel (''Eudromias morinellus''), also known in Europe as just dotterel, is a small wader in the plover family of birds. It is the only species placed in the genus ''Eudromias''. The dotterel is a brown-and-black-streaked bird ...
s, and
lapwing Lapwings (subfamily Vanellinae) are any of various ground-nesting birds (Family (biology), family Charadriidae) akin to plovers and dotterels. They range from in length, and are noted for their slow, irregular wingbeats in flight and a shrill, ...
s. The snowy plover was originally described by
John Cassin John Cassin (September 6, 1813 – January 10, 1869) was an American ornithology, ornithologist from Pennsylvania. He worked as curator and vice president at the Philadelphia Academy of Natural Sciences and focused on the systemic classification ...
in 1858, but was classified as a
subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
of the
Kentish plover The Kentish plover (''Anarhynchus alexandrinus'') is a small wader () of the family Charadriidae that breeds on the shores of saline lakes, lagoons, and coasts, populating sand dunes, marshes, semi-arid desert, and tundra.Székely, T., A. Argüel ...
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 The Gulf Coast of the United States, also known as the Gulf South or the South Coast, is the coastline along the Southern United States where they meet the Gulf of Mexico. The coastal states that have a shoreline on the Gulf of Mexico are Tex ...
, and on
Caribbean The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...
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 Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
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 Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and ch ...
, 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 In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
or
soda lake A soda lake or alkaline lake is a lake on the strongly base (chemistry), basic side of neutrality, typically with a pH, pH value between 9 and 12. They are characterized by high concentrations of carbonate salts, typically sodium carbonate (and ...
s, where it feeds on invertebrates such as
crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...
s, 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 Polygamy (from Late Greek , "state of marriage to many spouses") is the practice of marriage, marrying multiple spouses. When a man is married to more than one wife at the same time, it is called polygyny. When a woman is married to more tha ...
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 California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
– and the more pronounced this sex ratio imbalance is, the more females engage in polyandrous behavior. The snowy plover is listed as
near threatened A near-threatened species is a species which has been Conservation status, categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature (IUCN) as that may be vulnerable to Endangered species, endangerment in the ne ...
by the
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...
. The main threats are
habitat destruction Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...
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 predator Egg predation or ovivory is a feeding strategy in many groups of animals (ovivores) in which they consume eggs. Since a fertilized egg represents a complete organism at one stage of its life cycle, eating an egg is a form of predation, the killi ...
s. 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 John Cassin (September 6, 1813 – January 10, 1869) was an American ornithology, ornithologist from Pennsylvania. He worked as curator and vice president at the Philadelphia Academy of Natural Sciences and focused on the systemic classification ...
in 1858 as ''Aegialitis nivosa'', based on a skin collected in 1854 by
William P. Trowbridge William Petit Trowbridge (May 25, 1828 – August 12, 1892) was a mechanical engineer, military officer, and naturalist. He was one of the first mechanical engineers on the faculties of the University of Michigan, the Sheffield Scientific School ...
in
Presidio A presidio (''jail, fortification'') was a fortified base established by the Spanish Empire mainly between the 16th and 18th centuries in areas under their control or influence. The term is derived from the Latin word ''praesidium'' meaning ''pr ...
, which later became part of
San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
. This skin, the
holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
of the species, was subsequently lost. Although originally part of the collection of the
National Museum of Natural History The National Museum of Natural History (NMNH) is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. With 4.4 ...
, 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 The Victoria University of Manchester, usually referred to as simply the University of Manchester, was a university in Manchester, England. It was founded in 1851 as Owens College. In 1880, the college joined the federal Victoria University. A ...
, but the skin was apparently not part of this transfer.
Joseph Grinnell Joseph P. Grinnell (February 27, 1877 – May 29, 1939) was an American field biologist and zoologist. He made extensive studies of the fauna of California, and is credited with introducing a method of recording precise field observations known ...
, 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.
Plover Plovers ( , ) are members of a widely distributed group of wader, wading birds of subfamily Charadriinae. The term "plover" applies to all the members of the subfamily, though only about half of them include it in their name. Species lis ...
s (Charadriinae) are a
subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...
of small shorebirds that breed in open habitats on all continents except Antarctica. Together with the
lapwing Lapwings (subfamily Vanellinae) are any of various ground-nesting birds (Family (biology), family Charadriidae) akin to plovers and dotterels. They range from in length, and are noted for their slow, irregular wingbeats in flight and a shrill, ...
s (Vanellinae), they form the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Charadriidae The bird family Charadriidae includes the plovers, dotterels, and lapwings. The family contains 69 species that are divided into 10 genera. Taxonomy The family Charadriidae was introduced (as Charadriadæ) by the English zoologist William El ...
. The snowy plover was traditionally considered to be a species within the genus ''
Charadrius ''Charadrius'' is a genus of plovers, a group of wading birds. The genus name ''Charadrius'' is a Late Latin word for a yellowish bird mentioned in the fourth-century Vulgate. They are found throughout the world. Many ''Charadrius'' species are ...
'', 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 A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
(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 ''Anarhynchus'' is a genus of plovers consisting of 24 species. Many ''Anarhynchus'' species are characterised by partial collars, rather than full breast bands or collars which are characteristic of ''Charadrius''. Taxonomy French naturalis ...
'', as ''Anarhynchus nivosus'', along with 22 other plover species; in 2023, this transfer was recognized by the
International Ornithologists' Union The International Ornithologists' Union (IOU) is an international organization for the promotion of ornithology Ornithology, from Ancient Greek ὄρνις (''órnis''), meaning "bird", and -logy from λόγος (''lógos''), meaning "study", ...
. Before the transfer, ''Anarhynchus'' contained only one species, the
wrybill The wrybill or (in Māori language, Māori) ngutuparore (''Anarhynchus frontalis'') is a species of plover Endemic (ecology), endemic to New Zealand. It is the only species of bird in the world with a beak that is bent sideways in one direction, ...
from New Zealand. The name ''Anarhynchus'' derives from the
Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
() meaning and () meaning . The species name is
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
for . 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 The red-capped plover (''Anarhynchus ruficapillus''), also known as the red-capped dotterel, is a small species of plover. It breeds in Australia. This species is closely related to (and sometimes considered conspecific with) the Kentish plover, ...
, as shown in a
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
from a 2015 study: The snowy plover is closely related, and visually similar, to the Kentish plover of
Eurasia Eurasia ( , ) is a continental area on Earth, comprising all of Europe and Asia. According to some geographers, Physical geography, physiographically, Eurasia is a single supercontinent. The concept of Europe and Asia as distinct continents d ...
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 A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...
and
nuclear DNA Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. ...
, snowy plovers differ from Kentish plovers in being smaller, having shorter and wings, different chick plumages, and different advertisement calls of the males. In 2011, the
International Ornithological Congress International is an adjective (also used as a noun) meaning "between nations". International may also refer to: Music Albums * ''International'' (Kevin Michael album), 2011 * ''International'' (New Order album), 2002 * ''International'' (The T ...
(IOC) and the
American Ornithologists' Union The American Ornithological Society (AOS) is an ornithological organization based in the United States. The society was formed in October 2016 by the merger of the American Ornithologists' Union (AOU) and the Cooper Ornithological Society. Its ...
(AOU) recognized them as separate species.


Subspecies

Two to three subspecies are commonly recognized: *'' Anarhynchus nivosus nivosus'' ( Cassin, 1858): The
nominate subspecies In biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. ...
, found in North America west of
Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...
. *''Anarhynchus nivosus tenuirostris'' (
Lawrence Lawrence may refer to: Education Colleges and universities * Lawrence Technological University, a university in Southfield, Michigan, United States * Lawrence University, a liberal arts university in Appleton, Wisconsin, United States Preparator ...
, 1862)
: The Cuban snowy plover, found in North America east of Louisiana. The distinction of this subspecies from the ''nivosus'' subspecies is contested, but two genetic analyses in 2007 and 2020 have supported its separation. *''Anarhynchus nivosus occidentalis'' (
Cabanis Cabanis is a surname. Notable people with the surname include: * Bernard Cabanis (born 1950), French ice hockey player * George Cabanis (1815–1892), American politician * James Cabanis (1838–1920), American politician, son of George Cabanis *Jea ...
, 1872)
: Found on the Pacific coast of South America. It is slightly larger than the nominate subspecies, the (the area between eye and beak) is white, and the black patch on the forehead is slightly broader. A 2020 study suggested that the snowy plover populations can be subdivided into four distinct
demes In Ancient Greece, a deme or (, plural: ''demoi'', δήμοι) was a suburb or a subdivision of Athens and other city-states. Demes as simple subdivisions of land in the countryside existed in the 6th century BC and earlier, but did not acquire ...
(groups of individuals more genetically similar to each other than to other individuals): The western ''nivosus'' deme in western North America, the eastern ''nivosus'' deme in
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
, the ''tenuirostris'' deme on the
Caribbean The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...
islands and
Bermuda Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest. Bermuda is an ...
, and the ''occidentalis'' deme in South America. The study found little genetic exchange between these demes, except for a strong migration from the western to the eastern ''nivosus'' deme (but not vice versa).


Description

The snowy plover is a plump shorebird with a large head, a short and slender bill, and short neck and tail. It is a small plover, with adults ranging from in length, from in wingspan, and from in weight. Its body is typically held horizontally. Compared to other plovers, its legs are relatively long and its wings short. The bill is black, the
iris Iris most often refers to: *Iris (anatomy), part of the eye * Iris (color), an ambiguous color term *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (given name), a feminine given name, and a list of peopl ...
dark brown, and the legs gray to black. Snowy plovers are pale brown above and white below, with a white band on the hind neck and a smudgy (absent in the South American subspecies). Breeding males have black patches behind the eye ("ear patch"), on the sides of the neck, and on the forehead. In males, the may be reddish at the start of the breeding season. The breeding female is slightly duller, and typically one or more of the patches are partly or completely brown. The neck patches on each side are well separated and rarely joined at the front, giving the appearance of a "broken" breast band in contrast to the continuous breast band in many other plovers. Outside the breeding season, the neck and ear patches are pale and the forehead patch is absent, and plumages of males and females cannot be distinguished. Newly hatched chicks have pale upper sides with brown to black spots and are white below. Similar species within its range include the
piping plover The piping plover (''Charadrius melodus'') is a small sand-colored, Passerellidae, sparrow-sized wader, shorebird that nests and feeds along coastal sand and gravel beaches in North America. The adult has yellow-orange-red legs, a black band acro ...
, the
collared plover The collared plover (''Anarhynchus collaris'') is a small shorebird in the plover family, Charadriidae. It lives along coasts and riverbanks of the tropical to temperate Americas, from central Mexico south to Chile and Argentina. This small plov ...
, the
semipalmated plover The semipalmated plover (''Charadrius semipalmatus'') is a small plover. ''Charadrius'' is a Late Latin word for a yellowish bird mentioned in the fourth-century Vulgate. It derives from Ancient Greek ''kharadrios'' a bird found in ravines and ri ...
, and
Wilson's plover Wilson's plover (''Anarhynchus wilsonia'') is a small bird of the family Charadriidae. It was named after the Scottish-American ornithologist Alexander Wilson by his friend George Ord in 1814. Wilson's plover is a coastal wader which breeds ...
. Amongst other features, the snowy plover differs from these species in its slender and entirely black bill (shorter and thicker in piping plover and longer and thicker in Wilson's plover, and with orange base in piping and breeding semipalmated plover), in its gray to black legs (orange or yellow in piping, collared, and semipalmated plover), and the "broken" breast band (usually complete in semipalmated, Wilson's, and breeding collared plovers).


Vocalizations

The typical
call Call or Calls may refer to: Arts, entertainment, and media Games * Call (poker), a bet matching an opponent's * Call, in the game of contract bridge, a bid, pass, double, or redouble in the bidding stage Music and dance * Call (band), from L ...
is a repeated "tu-wheet" given in a wide range of contexts. In males, these include advertisement while standing in territories and courtship. In both sexes, the call may be given in situations of threat, aggression, distress, and alarm. This call differs between sexes, being shorter, quieter, and hoarser in the female. Other calls include a repeated "purrt" that is given during breeding season, for example while flying from nest sites or when other plovers intrude their territory. A single "churr" is mostly given by males while defending territory or offspring from other plovers. Outside the breeding season, a repeated "ti" is given when disturbed while resting, and is often followed by flight. Chicks make a "peep" call from up to two days before hatching while still in the egg, and until their first flight.


Distribution and habitat

The snowy plover is distributed along the Pacific coast of North and South America, in areas inland of the US and Mexico, along the coast of the
Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...
, and on the Caribbean islands and Bermuda. On the Pacific coast, it breeds from south
Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...
down to
Oaxaca Oaxaca, officially the Free and Sovereign State of Oaxaca, is one of the 32 states that compose the political divisions of Mexico, Federative Entities of the Mexico, United Mexican States. It is divided into municipalities of Oaxaca, 570 munici ...
in Mexico, and non-breeding individuals can be found as far south as Panama. In South America, it breeds from south Ecuador to
Chiloé Island Chiloé Island (, , ), also known as Greater Island of Chiloé (''Isla Grande de Chiloé''), is the largest island of the Chiloé Archipelago off the west coast of Chile, in the Pacific Ocean. The island is located in southern Chile, in the Los L ...
in Chile. In the Caribbean, breeding occurs eastwards as far as the
Virgin Islands The Virgin Islands () are an archipelago between the Atlantic Ocean, North Atlantic Ocean and northeastern Caribbean Sea, geographically forming part of the Leeward Islands of the Lesser Antilles in the Caribbean, Caribbean islands or West Indie ...
and
Margarita Island Margarita Island (, ) is the largest island in the States of Venezuela, Venezuelan state of Nueva Esparta, situated off the north west coast of the country, in the Caribbean Sea. The capital city of Nueva Esparta, La Asunción, is located on the ...
. The coastal populations consist of both migratory and residential birds; migration occurs over relatively short distances north- or southward along the coast. Inland breeding populations exist in the US eastward to the
Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...
of
Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...
and
Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...
, as well as in Mexico north of
Mexico City Mexico City is the capital city, capital and List of cities in Mexico, largest city of Mexico, as well as the List of North American cities by population, most populous city in North America. It is one of the most important cultural and finan ...
. These populations are mostly migratory, with western populations migrating to the Pacific coast, and the Great Plains populations to the Gulf of Mexico coast. Breeding has been recorded at elevations up to . The species inhabits open areas in which vegetation is absent or sparse, in particular coastal sand beaches and shores of
salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
or
soda lake A soda lake or alkaline lake is a lake on the strongly base (chemistry), basic side of neutrality, typically with a pH, pH value between 9 and 12. They are characterized by high concentrations of carbonate salts, typically sodium carbonate (and ...
s. It also breeds on river bars that are located close to the coast, and adopts human-made habitats such as wastewater and salt evaporation ponds, dammed lakes, and dredge spoils. It requires the proximity of water, although it may breed on salt flats where only very little water remains.


Behavior and ecology


Feeding

The species feeds on invertebrates such as
crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...
s, worms,
beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...
s, and
flies Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwin ...
. An analysis of feces from a coastal population in
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
during breeding season found beetles in 72%, flies in 44%, and insect larvae in 25% of the feces. Prey is taken from above and below the sand surface, from plants, and from carcasses. In inland habitats, snowy plovers usually forage on wet substrates that may be under a shallow water cover. As is typical for plovers, prey is found visually by briefly standing to scan the area, followed by running and capturing. Snowy plovers also forage by probing the substrate with their bills, by charging or hopping into accumulations of flies, and by "foot trembling" on wet substrates or in shallow water, where one foot shakes to stir up prey.
Brine fly Ephydridae (shore flies, sometimes brine flies) is a family of insects in the order Diptera. Shore flies are tiny flies that can be found near seashores or at smaller inland waters, such as ponds. About 2,000 species have been described worldwide ...
larvae are often shaken before consumption, and captured flies are often bitten two or three times. Snowy plovers may forage during day and night, with one individual observed feeding in almost complete darkness. Snowy plovers drink when fresh water is available, but when it is not, they can sustain themselves on the water content of their prey.


Territoriality and roosting

At the beginning of the breeding season, the male, while still unpaired, will establish and defend a territory, which is then advertised to a female by calling and excavating scrapes. A pair will continue to defend the territory. After the chicks hatch, the family will soon begin to move around, when the adults will defend the surrounding radius rather than a fixed territory. When defending a territory, males may attempt to intimidate intruders by using the "Upright Display" posture, in which the body is upright with erected breast feathers. They may also run or fly at, or fight with intruders. Fighting may involve jumping at each other breast-to-breast with flapping wings and mutual pecking and shoving. In some cases, combatants pull on each other's feathers, and may even pull out a tail feather. Fights with intermittent short breaks can last up to 1.5 hours. Territories are defended not only against other snowy plovers but also against some other bird species, including semipalmated plovers and whimbrels. Territories are probably not important for protecting food resources, as the plovers often feed in flocks up to away from their territories. In Kansas and Oklahoma, where the birds are more stationary, protection of feeding grounds could be more important. The size of territories is variable, and sizes between have been reported. Outside the breeding season, snowy plovers will often roost in groups of several to more than 300 birds. Roosting places are typically on the ground, often in depressions such as footprints (including those of humans) and vehicle tracks or behind objects such as driftwood.


Breeding

Snowy plovers are facultatively
polygamous Polygamy (from Late Greek , "state of marriage to many spouses") is the practice of marrying multiple spouses. When a man is married to more than one wife at the same time, it is called polygyny. When a woman is married to more than one h ...
, with females, and less frequently males, often abandoning their mate soon after the chicks have hatched. The deserting female will then pair with a new male and renest, sometimes a few hundred kilometers away from its first brood, while the male will continue to rear the chicks. A 2021 study of a population at , Mexico, found that females are more likely to abandon their broods when the chicks are likely to survive even in their absence, or when the chicks have a low probability of survival. The polygamy in this species could therefore be a strategy to maximize breeding success. Polygamy is most pronounced where the breeding season is long, when birds may start two, and sometimes three, broods per season. On the other hand, birds do generally not brood twice in the Great Plains, where the breeding season is short. A biased sex ratio also appears to favor polygamy: males are generally more common than females, with one study reporting that males were 1.4 times more common than females in California. The causes for such pronounced sex ratios are unknown. Rarely, males breed with two females at the same time. Pairs can also be reestablished in the next breeding season, which occurred in 32 to 45% of cases in central California, or within the same season in the third breeding attempt of the female. The polygamous mating system of the snowy plover is uncommon in birds, but the closely related Kentish plover shows a similar behavior. Snowy plovers nest in nest scrapes that are excavated by the male as an important part of the courtship ritual. In the coastal areas of California, males excavated an average of 5.6 scrapes per territory. A scrape may be constructed within a few minutes, often near conspicuous landmarks such as rocks and grass patches. One of these scrapes is later selected by the pair for nesting, commonly the scrape where most copulations took place. Both before and during incubation, the adults continue to line the nest with small objects such as stones and shell pieces. Where the ground is too hard to construct scrapes, other depressions such as animal and vehicle tracks are chosen. The species lays three eggs on average, but clutch size ranges from two to six eggs. When only a single egg is produced, the clutch is usually abandoned. Eggs are oval or asymmetric in shape and have a matte and smooth surface. In coastal California, they average at in length, in width, and in weight, which accounts for 20% of the body weight of the female. Egg color is brownish-yellow, with dark brown or black speckles that become more numerous towards the blunt end of the egg. The female lays one egg every 47 to 118 hours until the clutch is complete. The time interval between egg laying and hatching varies geographically and seasonally, ranging between 23 and 49 days. Continuous incubation starts upon clutch completion; while still incomplete, males and females spend only about a quarter of the daytime incubating. In coastal areas of California, females tend to incubate during the day, while males incubate at night. The reason for this pattern is unclear, and hypotheses include a need of the female to feed at night to regain energy lost from egg laying and the need of the male to defend the territory during daytime. Under hot conditions greater , the male and female take turns at least once per hour. A day before hatching, chicks and parents begin to communicate by calling. After hatching, the parents will carry eggshells away from the nest. The chicks are
precocial Precocial species in birds and mammals are those in which the young are relatively mature and mobile from the moment of birth or hatching. They are normally nidifugous, meaning that they leave the nest shortly after birth or hatching. Altricial ...
and able to walk and swim one to three hours after hatching. Parents do not feed their chicks, but will lead them to feeding areas. Parents will continue to brood their chicks after hatching – in the coastal areas of northern California, chicks less than 10 days old were brooded for an average of 58% of each day. In western North America, chicks are looked after for 29 to 47 days after hatching, often by the male after the female has deserted. In the more eastern populations, however, chicks are often cared for until they fledge.


Predators and mortality

Adults are preyed upon by
birds of prey Birds of prey or predatory birds, also known as (although not the same as) raptors, are hypercarnivorous bird species that actively predation, hunt and feed on other vertebrates (mainly mammals, reptiles and smaller birds). In addition to speed ...
and various mammals including
feral cat A feral cat or a stray cat is an unowned domestic cat (''Felis catus'') that lives outdoors and avoids human contact; it does not allow itself to be handled or touched, and usually remains hidden from humans. Feral cats may breed over dozens ...
s and
fox Foxes are small-to-medium-sized omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull; upright, triangular ears; a pointed, slightly upturned snout; and a long, bushy tail ("brush"). Twelve species ...
es, with a wider range of predators preying on chicks and eggs. Adults will usually run away from an approaching predator or human, but may also take flight. Approaching birds of prey cause adults to duck on their nests, while roosting flocks will take flight to form a highly coordinated flight formation in which they move back and forth. Parents will signal their chicks to lie flat against the ground when sensing potential danger. They may then attempt to distract predators from their chicks by calling and flying around. Parents also use injury feigning, when they will run away and move their wings as if they are broken, or lie on the ground while crouching or flapping. Common diseases include
botulism Botulism is a rare and potentially fatal illness caused by botulinum toxin, which is produced by the bacterium ''Clostridium botulinum''. The disease begins with weakness, blurred vision, Fatigue (medical), feeling tired, and trouble speaking. ...
, and common parasites include bird lice. The average life span has been estimated at 2.7 years, and the oldest snowy plover on record was at least 15 years old.


Status and conservation

The snowy plover is among the rarest
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
shorebirds in the Americas. Since 2014, it is listed as "
Near Threatened A near-threatened species is a species which has been Conservation status, categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature (IUCN) as that may be vulnerable to Endangered species, endangerment in the ne ...
" by the
IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...
because of a moderately rapid population decline caused primarily by habitat degradation and human disturbance. In the US Pacific coast, the species is thought to have lost 50 out of 78 breeding sites since 1970, and in the Great Plains of
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
, the decline is estimated to have been larger than 75% between 1998 and 2009. Subtropical and tropical populations, although less studied and monitored than those of higher latitudes, may be similarly threatened. As of 2020, the global population is estimated at 24,000 to 31,000 mature individuals. Counting both juveniles and mature individuals, the North American population has been estimated at 25,869; the population in and around the Gulf of Mexico at 2,500; and the South American population at 8,000 to 10,000 individuals.


Causes of decline

Habitat degradation is a major cause for the declines in both coastal and inland populations in the US. Many coastal beaches have been developed for recreational use. Periodic raking of beaches to remove garbage and natural debris such as kelp causes plovers to abandon breeding areas, and reduces biodiversity and biomass of the invertebrates the plovers feed on. Dune habitat was lost to the invasive European beachgrass, which had originally been planted to stabilize dunes. This species, as well as the American beachgrass from the Atlantic coast, have replaced native foredune vegetation in most of the North American Pacific coast. In the Great Salt Plains in Oklahoma, controlled flooding, as well as an invasive shrub, the French tamarisk, have destroyed much plover habitat. In the Great Plains of Texas, sinking groundwater levels due to water extraction has been identified as the primary cause of decline. River habitats in Kansas and Oklahoma have been decimated by the extraction of water, the erection of water reservoirs, and vegetation growth. Habitat is lost to housing and urbanization adjacent to beaches. Less significant are habitat losses due to the trapping of
sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
s by dams and
jetties A jetty is a man-made structure that protrudes from land out into water. A jetty may serve as a breakwater, as a walkway, or both; or, in pairs, as a means of constricting a channel. The term derives from the French word ', "thrown", signif ...
that affect coastal
erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
and
sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to th ...
. Habitat degradation is also a major concern for populations of lower altitudes. For example, around Ceuta in Mexico, the species is affected by large-scale removal of protected
mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...
forests and illegal development of beaches, but also by the spread of mangroves into abandoned evaporation ponds that were adopted as habitats by the plovers. A 2017 analysis concluded that the Ceuta population will probably be extinct in 25 years if no further conservation measures are implemented. On US beaches, disturbance by humans and dogs is another significant cause for the abandonment of areas. One 2001 study found that at a public beach at
Coal Oil Point The Coal Oil Point seep field (COP) in the Santa Barbara Channel offshore from Goleta, California, is a marine petroleum seep area of about three square kilometres, within the Offshore South Ellwood Oil Field and stretching from the coastline s ...
, each plover was disturbed every 27 minutes on average during weekends and every 43 minutes during the week. The study further found that the plovers have been more sensitive to dogs than to humans, and that most disturbances occurred when the plovers were approached by less than . A 2003 study of two beaches at
Point Reyes National Seashore Point Reyes National Seashore is a park preserve located on the Point Reyes, Point Reyes Peninsula in Marin County, California. As a national seashore, it is maintained by the US United States National Park Service, National Park Service as an ...
found that chick mortality was 69% greater on weekends compared to weekdays in 1999 and 72% greater in 2000, demonstrating the negative effects of human recreation. Nests have also been directly crushed by vehicles, walking humans, and, in inland populations, by cattle. An experiment with
quail Quail is a collective name for several genera of mid-sized birds generally placed in the order Galliformes. The collective noun for a group of quail is a flock, covey, or bevy. Old World quail are placed in the family Phasianidae, and New ...
eggs at Sands Beach in
Santa Barbara County Santa Barbara County, officially the County of Santa Barbara (), is a county located in Southern California. As of the 2020 United States census, the population was 448,229. The county seat is Santa Barbara, and the largest city is Santa M ...
, California, revealed an 8% daily risk of eggs being trampled by humans when outside protected areas. Several additional threats have been documented. Predation on chicks and eggs by crows, ravens,
skunk Skunks are mammals in the family Mephitidae. They are known for their ability to spray a liquid with a strong, unpleasant scent from their anal glands. Different species of skunk vary in appearance from black-and-white to brown, cream or gi ...
s, and invasive
red fox The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe and Asia, plus ...
es has intensified in some areas. Crows and ravens may be attracted to plover breeding areas by human food sources. Several instances have been documented where environmental pollution affected populations.
Oil spill An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...
s have been a repeated threat, such as the New Carissa spill of 1999 that is known to have killed a minimum of 45 plovers. At Point Reyes National Seashore, mercury contamination has been identified as the cause for a high proportion of unhatched eggs. A 2018 study found that 98% of analyzed plovers in the Southern Great Plains had blood
selenium Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elem ...
levels exceeding the toxicity threshold. Discarded
monofilament fishing line Monofilament fishing line (shortened to just mono) is fishing line made from a single fiber of plastic material, as opposed to multifilament or braided fishing lines constructed from multiple strands of fibers. Most fishing lines are now nylon ...
s are a known threat, but their impact on populations is unknown. In the future,
effects of climate change Effects of climate change are well documented and growing for Earth's natural environment and human societies. Changes to the climate system include an Instrumental temperature record, overall warming trend, Effects of climate change on the ...
, such as droughts and habitat loss due to
sea level rise The sea level has been rising from the end of the last ice age, which was around 20,000 years ago. Between 1901 and 2018, the average sea level rose by , with an increase of per year since the 1970s. This was faster than the sea level had e ...
, are likely to become significant threats.


Conservation measures

In 1993, the Pacific coast population of the US was listed as a "threatened" under the
Endangered Species Act of 1973 The Endangered Species Act of 1973 (ESA; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting and conserving imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of e ...
, and a recovery plan followed in 2007. The plan focuses on three main conservation measures: closure of upper beach areas to the public during breeding season; protection against predators; and habitat restoration. Closure of beach areas was most effective when including fencing against dogs and a 30 m buffer zone.
Egg predator Egg predation or ovivory is a feeding strategy in many groups of animals (ovivores) in which they consume eggs. Since a fertilized egg represents a complete organism at one stage of its life cycle, eating an egg is a form of predation, the killi ...
s were controlled by both fencing individual nests and predator removal. Habitat restoration focused on the removal of the invasive European beachgrass. Measures are also in place to protect some other snowy plover habitats elsewhere in the US. In the Great Salt Plains in Oklahoma, dams and fences were erected around nesting areas to prevent flooding and predation, but proved ineffective. In Mexico, the species has been listed as "threatened" since 2010. Even though the global population is declining, conservation efforts have led to local increases in plover populations. In central Chile, protection of a small stretch of beach against human disturbance resulted in an increase of the local population, as was reported in 2001. The first instance of snowy plovers reoccupying a breeding area following its protection from human disturbance was documented in 2006 at Sands Beach, Santa Barbara County, where barriers are in use since 2001. As of March 2023, conservation efforts have been particularly successful in
Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...
, where numbers increased to 483 birds, from just 55 birds in 1993. This increase was possible due to roping off of dry sand on beaches, as well as the removal of invasive grasses. In California, the population is estimated at 1,830 birds as of March 2023.


References


External links


Western Snowy Plover - Tools and Resources for Recovery
* * * * * {{Taxonbar, from=Q1263624
snowy plover The snowy plover (''Anarhynchus 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 ...
snowy plover The snowy plover (''Anarhynchus 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 ...
Birds of the Americas Birds of the United States Birds of Central America Birds of the Dominican Republic Western South American coastal birds Fauna of the San Francisco Bay Area
snowy plover The snowy plover (''Anarhynchus 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 ...
snowy plover The snowy plover (''Anarhynchus 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 ...