occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Breeding
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Breeding range includes the following regions: North American Pacific coast from Washington south to Oaxaca (Mexico) (most numerous from San Francisco Bay south); Pacific coast of South America from Ecuador to Chile; inland areas of North America locally from Saskatchewan (irregular) and Montana (irregular) south to central Mexico; Gulf Coast from Florida to southern Mexico; and locally on islands of the Bahamas and Caribbean region (Page et al. 2009). Approximately 42 percent of all breeding Snowy Plovers in North America occur in only tow areas (Great Salt Lake, Utah, and Salt Plains National Wildlife Refuge, Oklahoma) (Thomas et al. 2012).
Nonbreeding range encompasses islands and coastal areas (and some inland sites) locally from southern Washington south to Chile, Gulf of Mexico coast of the United States and Mexico, Bahamas, Caribbean islands, and islands along northern South America (Page et al. 2009).
Length: 16 cm
Weight: 41 grams
Differs from subspecies TENUIROSTRIS in being much darker dorsally (light hair brown to nearly drab vs. pale drab-gray to nearly grayish white in TENUIROSTRIS) (Ridgway 1919).
Habitat and Ecology
Comments: Habitat includes beaches, dry mud or salt flats, and sandy shores of rivers, lakes, and ponds.
The Pacific coast population breeds primarily above the high tide line on coastal beaches, sand spits, dune-backed beaches, sparsely vegetated dunes, beaches at creek and river mouths, and salt pans at lagoons and estuaries. Less common nesting habitats include bluff-backed beaches, dredged material disposal sites, salt pond levees, dry salt ponds, and river bars. In winter, this species is found on many of the beaches used for nesting as well as on beaches where they do not nest, in man-made salt ponds, and on estuarine sand and mud flats. Source: USFWS (2007).
Nests are on the ground on broad open beaches or salt or dry mud flats, where vegetation is sparse or absent (small clumps of vegetation are used for cover by chicks); nests generally are beside or under objects or in open (Page et al. 1985). Nests often are subject to flooding. In northern Utah, snowy plovers usually nested in areas devoid of vegetation and selected brine fly exuviae for a nesting substrate when available (Paton and Edwards 1991); nesting generally occurred in recently exposed alkaline flats (Paton and Edwards 1992).
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
See record for C. ALEXANDRINUS.
Comments: Eats insects, small crustaceans, and other minute invertebrates (Terres 1980). Picks food items from substrate, probes in sand or mud in or near shallow water, sometimes uses foot to stir up prey in shallow water.
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 81 - 300
Comments: This species is represented by a large number of relatively small local populations.
Historical nesting range of the federally listed Pacific coast population included 87 sites (5 in Washington, 29 in Oregon, and 53 in California); currently nesting occurs apparently in only 28 sites (2 in Washington, 6 in Oregon, and 20 in California).
Revised designated critical habitat of the Pacific Coast distinct population segment encompasses 4 units in Washington, 9 units in Oregon, and 47 units in California; all but 9 of these 60 units are regarded as currently occupied by snowy plovers (USFWS 2012).
10,000 - 100,000 individuals
Comments: During 2007 and 2008, 557 discrete wetlands were surveyed and nine additional large wetland complexes sampled in México and the USA. From these surveys, a population of 23,555 (95% CI = 17,299 - 29,859) breeding snowy plovers was estimated. Combining the estimate with information from areas not surveyed, the total North American population was assessed at 25,869 (95% CI = 18,917 - 32,173) (Thomas et al. 2012).
Breeding population size in the Caribbean-Bahamas region is unknown but likely small. Breeding population size in coastal South America is unknown, but the species is at least locally common (e.g., see Küpper et al. 2011).
Nonbreeding: usually solitary or in twos, though may form pre-migratory flocks of hundreds in some areas (Paton et al. 1992).
Mean annual survival rate was at least 69% (range 58-88%) for a migratory population at the Great Salt Lake, minimally 75% for a mixed migratory-resident population in coastal California, 66% for a migratory population in North Dakota (see Paton 1994). Predation by gulls, common raven, red fox, skunk, raccoon, and/or coyote may result in a high rate of clutch loss in some areas (Page et al. 1983, 1985; Paton and Edwards 1991, 1992).
Life History and Behavior
Clutch initiation in northern Utah ranged from mid-April to mid-July (Paton and Edwards 1991, 1992). Clutch size usually is 3. Incubation lasts 24 days, by both sexes. Young are tended by both sexes (or male only), leave nest soon after hatching, fly at 22-31 days. Double brooding commonly occurs in California; female abandons first mate and brood within a few days of hatching and renests with new mate. May nest in loose colony (maximum of 3.3 nests/ha in California). In northern Utah, nest spacing was clumped at certain sites, rather than widely dispersed as has been reported for eastern California (Paton and Edwards 1991).
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N1B - Critically Imperiled
Rounded National Status Rank: N3B,N3N : N3B: Vulnerable - Breeding, N3N: Vulnerable - Nonbreeding
NatureServe Conservation Status
Rounded Global Status Rank: G3 - Vulnerable
Reasons: Large but discontinuous range extending from North America to South America; populations are scattered and declining in many areas, due to habitat loss/degradation, disturbance by humans, and/or impacts of non-native and native predators; much of overall population is concentrated in relatively few areas; many populations are vulnerable to declines resulting from factors associated with climate change.
Global Short Term Trend: Unknown
Comments: Trend over the past 10 years or three generations is unknown. Regional populations in interior North America tend to fluctuate annually with water levels (Thomas et al. 2012). Population increases associated with management occurred along the U.S. Pacific coast in the early 2000s (USFWS 2007).
Global Long Term Trend: Decline of 30-50%
Comments: Over the long term, this species has declined in distribution and abundance, but the precise level of decline is uncertain.
Abundance in Baja California appeared to decrease by 40 percent between the early 1990s and 2007-2008 (Thomas et al. 2012).
Population declines are apparent in the western United States and have been reported in the southern Great Plains region. Reports in the 1980s described declines in breeding pairs at coastal locations in California and Oregon and a decline in the number of birds wintering in California (Paton and Edwards 1990). The estimated population for Washington, Oregon, California, and Nevada declined about 20 percent between the late 1970s and late 1980s; often these declines were associated with changes in habitat availability (Page et al. 1991). The population in the San Joaquin Valley, California, increased between the late 1970s and late 1980s due to increased habitat availability at newly constructed agricultural waste water ponds (Page et al. 1991).
Degree of Threat: High
Comments: Poor reproductive success and probable negative effects on roosting and foraging plovers due to human disturbance (including recreational beach use and mechanical raking of beaches) are major problems in coastal areas of North and South America (USFWS 2007, Küpper et al. 2011).
Much habitat has been lost to beach-front development.
The spread of introduced beach grass limits the amount of suitable nesting habitat in some areas along the Pacific coast of North America. At the Great Salt Lake, Utah, expanding stands of the exotic common reed (Phragmites australis) eliminated extensive open areas previously used by nesting by snowy plovers (J. Cavitt, in litt., cited by Page et al. 2009). On the Great Plains, habitat has been lost to impoundments and invasion of non-native tamarisk (Hill 1993).
This species is increasingly vulnerable to predation and clutch loss from native and introduced mammals and birds (Page et al. 1995, 2009).
In Marin County, California, an unusually high proportion of clutches that failed to hatch contained high levels of mercury (Schwartzbach et al. 2005).
This species is vulnerable to oiling of the plumage as a result of oil spills (Mangan et al. 2001).
Snowy plovers sometimes have been injured or killed as a result of collisions or entanglement with fencing or netting used for predator exclosures (see Page et al. 2009).
Some populations are vulnerable to habitat loss/degradation and nest loss as a result of rising sea level and increased storm frequency/intensity or flooding associated with climate change.
The aggregation of breeding plovers at relatively few inland sites and along coastal beaches heavily used by humans make them continually vulnerable to population declines (Thomas et al. 2012).
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). 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 breedng areas and wintering sites. Evaluate key threats. Continue predator exclusions and protective barriers to prevent disturbance at key nesting areas.
Global Protection: Few to several (1-12) occurrences appropriately protected and managed
Relevance to Humans and Ecosystems
Stewardship Overview: The recovery plan for the North American Pacific coast population indicates that closing upper beach areas to the public during the nesting season, predator management, and habitat restoration (including removal of non-native invasive plants) are primary conservation actions that would benefit this species (USFWS 2007). Specific measures that are most needed vary regionally.
Nesting populations in some protected/managed areas have increased but have declined in other areas, suggesting that nonbreeding season factors may be important in the overall conservation status of this species.
Population increases along the Pacific coast in the 2000s were associated with implementation of management actions for the benefit of western snowy plovers and California least terns, including predator management and protection and restoration of habitat (USFWS 2007).
The recovery plan for the Pacific coast population listed the following conservation actions as appropriate:
1. Monitor breeding and wintering populations and habitats to determine progress of recovery actions
to maximize survival and productivity. 2. Manage breeding and wintering habitat to ameliorate or eliminate threats and maximize survival and productivity. 3. Develop mechanisms for long-term management and protection of western snowy plovers and their breeding and wintering habitat. 4. Conduct scientific investigations that facilitate recovery. 5. Conduct public information and education programs. 6. Review progress towards recovery and revise recovery efforts, as appropriate. 7. Dedicate U.S. Fish and Wildlife Service staff to allow the Arcata Fish and Wildlife Office to coordinate recovery implementation. 8. Establish an international conservation program with the government of Mexico to protect western snowy plovers and their breeding and wintering locations in Mexico.
|This article needs additional citations for verification. (September 2008)|
The western snowy plover (Charadrius nivosus) (pronounced "pluh-ver", rhyming with "glover") is a small wader in the plover bird family. It breeds in Ecuador, Peru, Chile, the southern and western USA and the Caribbean. Although it was long considered to be a subspecies of the Kentish plover, recent genetic research strongly suggests it should be regarded as a distinct species, and both the American Ornithologists' Union and the International Ornithological Congress recognise it as such.
The western snowy plover is 15–17 cm (5.9–6.7 in) long. It is smaller, paler, longer-legged and thinner-billed than ringed plover or semipalmated plover. Its breast band is never complete, and usually just appears as dark lateral patches on the sides of the breast. The snowy plover's upperparts are greyish brown and the underparts white in all plumages. The breast markings are black in summer adults, otherwise brown. Breeding males of some races have a black forehead bar and a black mask through the eye. The legs are black. In flight, the flight feathers are blackish with a strong white wing bar. The flight call is a sharp bip.
Genetic research published in 2009 strongly suggested that the snowy plover is a separate species from the Kentish plover, and by July, 2011, the IOC, and the AOU North American committee have recognized them as separate species. Other taxonomic committees are reviewing the relationship.
Physically, snowy plovers are shorter-legged, paler and greyer above than its Old World sister species, and breeding males lack a rufous cap. The eyemask is also poorly developed or absent.
The snowy plover breeds on sandy coasts and brackish inland lakes, and is uncommon on fresh water. It nests in a ground scrape and lays three to five eggs. The breeding birds in warmer countries are largely sedentary, but northern and inland populations are migratory, wintering south to the tropics. Food is insects and other invertebrates, which are obtained by a run-and-pause technique, rather than the steady probing of some other wader groups.
The western snowy plover breeds from Texas and Oklahoma west to California and up the coastline to Oregon and Washington, with the coastal form's primary breeding concentration in central and southern California. The Pacific Coast population has been designated a Threatened species under the Endangered Species Act.
In many parts of the world, it had become difficult for this species to breed on beaches because of disturbance from the activities of humans or their animals. The University of California, Santa Barbara, is currently endeavoring to rehabilitate snowy plover populations by protecting beaches along the central California coastline that runs along part of the university campus. UCSB has had some success in encouraging reproduction; the university also often trains students and other volunteers to watch over protected beaches during the daytime to ensure no one disturbs nesting grounds.
- Clemens Küpper, Jakob Augustin, András Kosztolányi, Terry Burke, Jordy Figuerola, Tamás Székely (2009). "Kentish versus Snowy Plover: phenotypic and genetic analyses of Charadrius alexandrinus reveal divergence of Eurasian and American subspecies". The Auk (The American Ornithologists’ Union) 126 (4).
- "Recovery Plan for the Pacific Coast Population of the Western Snowy Plover (Charadrius nivosus nivosus)". U.S. Fish and Wildlife Service. Retrieved 2009-10-01.
- "2003 UCSB Press Release on snowy plovers". World Heritage. Retrieved 2007-05-21.
- Gill, F and D Donsker (Eds). 2011. IOC World Bird Names (version 2.9). Available at http://www.worldbirdnames.org/ [Accessed July 31, 2011].
- Chesser, R. Terry, Richard C. Banks, F. Keith Barker, Carla Cicero, Jon L. Dunn, Andrew W. Kratter, Irby J. Lovette, Pamela C. Rasmussen, J. V. Remsen, James D. Rising, Douglas F. Stotz, Kevin Winker. 2011. Fifty-second supplement to the American Ornithologists' Union Check-List of North American Birds. Auk 128(3):600-613.
Names and Taxonomy
Comments: This species formerly was treated as conspecific with C. alexandrinus [Kentish Plover] of Eurasia (AOU 1983, 1998), but it is now separated on the basis of differences in male advertisement calls, morphology, and mitochondrial and nuclear DNA, which indicate that the African C. marginatus [Whitefronted Plover] is more closely related to C. alexandrinus or C. nivosus than these two species are to each other (Küpper et al. 2009). Some sources consider Charadrius nivosus, C. alexandrinus, C. marginatus, and the Australian C. ruficapillus [Red-capped Plover] to constitute a superspecies (Vaurie 1965, Mayr and Short 1970, Sibley and Monroe 1990), whereas others include C. javanicus [Javan Plover] in this superspecies (Rittinghaus 1961, Wiersma 1996) (AOU 2011 and sources cited therein).
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