Systematics

Editor’s Note: Formerly treated as conspecific with C. alexandrinus, the Kentish Plover of Eurasia, the Snowy Plover is now separated on the basis of differences in male calls, morphology, and mitochondrial and nuclear DNA. See Systematcis and the 52nd Supplement to the AOU Checklist of North American Birds for details. Future revisions of this account will reflect these changes.

Geographic Variation

Across North America, dorsal coloration pales from west to east, being palest in Gulf of Mexico and Caribbean populations. Birds in the Americas are grayer whereas birds in Eurasia (Kentish Plover, see Related Species, below) are browner, with the latter showing some clinal variation toward darker brown from west to east but, along the Asian coast, toward paler brown from north to south. Throughout the species’ range, the presence or absence of a loral stripe varies, it generally being absent in southerly populations. In breeding males, the width or presence of a black bar on the forecrown varies among populations, as does the hue or presence of a contrasting cinnamon crown. Leg color also varies.

Subspecies

Six subspecies in three groups, with perhaps as many as four species included under the current Charadrius alexandrinus umbrella. By contrast, two to three closely related species may be conspecific with a more broadly defined C. alexandrinus; see Related Species, below.

nivosus group (Snowy Plover):

C. a. nivosus (Cassin, 1858). Includes C. a. tenuirostris (Lawrence, 1862). Breeds spottily along Pacific Coast from sw. Washington south to Baja California Sur, across Great Basin from sw. Montana south to e. California and central Colorado, in parts of the desert Southwest, and in the Great Plains from s. Saskatchewan south to nw. Texas; many southerly populations are resident, including those along the Pacific Coast and at the Salton Sea, California, as well as at the n. Gulf of California, Mexican Plateau, Isthmus of Tehuantepec, Yucatan Peninsula, much of the Gulf of Mexico, the Bahamas, e. Cuba, Hispanoila, Puerto Rico, the Lesser and Netherlands Antilles, and Bermuda [type locality = Presidio, San Francisco Co., California]; otherwise winters around Gulf of California, across Pacific coast of Mexico, and around Gulf of Mexico. Approximate size of nominate subspecies (see below), but tarsi short (averaging < 26 mm); dorsum pale grayish brown; legs and feet dark gray; in the breeding male, crown concolorous with mantle, black bar on forecrown, black smudge at sides of breast, and lores dusky. Although C. a. “tenuirostris” of Puerto Rico was found to differ genetically (Funk et al. 2007), Blake (1977) remarked “so slight and nebulous is the [morphological] distinction that authorities differ not only on the respective winter ranges, but also on the allocation of breeding birds in the Southern Caribbean. Under the circumstances, no purpose is served in the recognition of two races.” Hayman et al. (1986) and Binford (1989) also merged the subspecies.

C. a. occidentalis (Cabanis, 1872). Resident along Pacific slope of South America from central Ecuador to central Chile [type locality = near Santiago, Chile]. Similar to C. a. nivosus but averages slightly larger, lores white, and black bar on forecrown slightly wider. Not surprisingly given the extent of geographic separation, this subspecies differs genetically from C. a. nivosus (Funk et al. 2007).

alexandrinus group (Kentish Plover [likely a separate species; see Küpper et al. 2009 and Related Species, below]):

C. a. alexandrinus Linnaeus, 1758. Includes C. cantianus (Latham, 1802), C. albifrons Wolf and Meyer, 1805, C. littoralis Bechstein, 1809, C. albigularis (Brehm, 1831), C. elegans (Lichtenstein, 1854), C. a. minor Seebohm, 1887, and C. minuta (Sharpe, 1896). Breeds across Western Palearctic, including Macaronesia, north to s. Steppe region, south to Cape Verde Islands off w. Africa and to the Horn of Africa, and e. to n. India [type locality = Egypt]; resident around Mediterranean and winters south to South Africa and Indian Subcontinent. Relatively large (wing > 104 mm, bill > 19.5 mm), with the tarsi long (averaging > 29 mm); dorsum medium brown; lower auriculars dark; legs and feet dark gray; in the breeding male, bright cinnamon crown contrasts with brown mantle, black bar on forecrown, black smudge at sides of breast, and lores black.

C. a. seebohmi Hartert and Jackson, 1915. Replacement name for C. a. minutus Seebohm, 1887. Resident of se. India and Sri Lanka [type locality = Sri Lanka]. Like nominate subspecies but smaller (wing < 106 mm, bill < 20.5 mm), lores dusky, and, in the breeding male, crown concolorous with mantle and lacks black bar on forecrown.

C. a. nihonensis Deignan, 1941. Breeds in s. Japan, including Ryukyu Is., e. Mongolia and China, and Taiwan [type locality = Aomori, Honshu, Japan]; winters south to Philippines, w. Indonesia, and Malay Peninsula. Like nominate subspecies but dorsum darker brown, crown of breeding male a richer cinnamon-orange, patches at side of breast more extensive (Chandler and Shirihai 1995, Leader 2001), and bill averages slightly heavier. For use of the name C. a. nihonensis for this taxon, see Kennerley et al. (2008).

dealbatus group (White-faced Plover):

C. a. dealbatus (Swinhoe, 1870). Breeds on the southern coast of China (Fujian province south to Guangxi province), likely including Hainan I. [type locality = Amoy Xiamen, Fujian province, China, fide Kennerley et al. 2008]; winters from s. Vietnam southwest to the length of the Malay Peninsula and to the n.-central coast of Sumatra (Kennerley et al. 2008). Similar to C. a. alexandrinus but averages longer and deeper bill; dorsum pale brown; patches on sides of breast small, pale, brown (not black) lores white; lower auriculars pale; in the breeding male, black bar on forecrown wider and orange crown somewhat duller; legs and feet pinkish gray. See Kennerley et al. (2008) for details on diagnosis.

Related Species

The family Charadriidae, the plovers and lapwings, is well supported and is one of the core groups in the shorebird (Charadriiformes) radiation. Within this family, the genus Charadrius is also well defined. A mitochondrial DNA-based phylogeny of thirteen members of the genus (Joseph et al. 1999) found C. alexandrinus to be sister to C. ruficapillus (the Red-capped Plover of Australia), and these two species, along with C. marginatus (the White-fronted Plover of sub-Saharan Africa) and C. javanicus (the Javan Plover of Java), form a superspecies (Wiersma 1996). On the basis of its geographic distribution and morphology, C. peronii (the Malaysian Plover of Indonesia and the Philippines) may also be an allospecies in this superspecies complex.

Species limits within this superspecies are open to debate. For example, Wiersma (1996) said of C. javanicus that it “may well not merit full species status” and noted that it is “often” treated conspecific with C. alexandrinus. At the other extreme, Howard and Moore (1994) treated C. a. occidentalis as a species despite its strong morphological similarity to C. a. nivosus (see also Sibley and Monroe 1990). Species limits of C. a. dealbatus are being explored currently (Kennerley et al. 2008), and it is possible that this taxon will be accord species status once its breeding range and behavior are elucidated fully.

It is also possible that taxa in the Old World and New World will be split from each other, a Kentish Plover vs. Snowy Plover split. Ridgley and Greenfield (2001) remarked that “American birds are perhaps better treated as a distinct species (C. nivosus) separate from those of the Old World; their calls appear to differ,” but provided no data in support. Küpper et al. (2009), however, provided data on molecular (mtDNA, a nuclear gene, and 26 microsatellites) divergence, as well as detailing differences in courtship calls and downy plumage of chicks. The genetic analyses demonstrated that C. a. alexandrinus is sister to C. marginatus, not to C. a. nivosus. If true, then the resultant paraphyly likely will lead taxonomists either to lump C. marginatus with the C. alexandrinus complex or split C. alexandrinus into Old World and New World species.