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Charadrius alexandrinusKentish plover(Also: snowy plover)

By Kelly Tague

Geographic Range

Charadrius alexandrinus breeds on most continents. In North America they breed locally in the western interior and on the Pacific and Gulf coasts. They also breed on the islands in the Caribbean and on coasts in Central America. In South America, they breed on the Humboldt Current coast and on the western coast. In Eurasia, breeding is more widespread in the interior and they also occur on the coasts of Asia, Europe, and northern Africa.

(Paulson, 1993)

Habitat

Snowy Plovers are primarily found on sand beaches, though they also forage on nearby mud flats, especially after breeding season. They also spend time on dune systems, coastal lagoons, inland steppes, sand deserts, tidal flats, dry salt flats, and large sandy rivers and lakes where there is little vegetation.

(Richards, 1988)

Physical Description

Charadrius alexandrinus are one of the smallest plovers, but they have proportionally longer legs. Plumage varies throughout the world with the American Snowy Plover being the palest. The upper parts of the body are pale in color. Breeding males have a small white forehead, black forecrown band, and a slightly reddish colored hindcrown. There is also a black eye band below a slim white brow. Male Snowy Plovers display a black shoulder patch and a complete white collar. Under parts of the bird are wholly white. Female Snowy Plovers have the same pattern as the male, but brown areas replace the black areas. In both sexes, the legs are dark gray, the eyes are large and black, and the bill is black and slender. North American Snowy Plovers have the same general pattern as Kentish Plovers (the name of Snowy Plovers in Europe), but the upper parts of the North American bird are a pale sandy gray color, and the breeding males have a pale fawn hindcrown. The legs are also a paler color in Snowy Plovers than in Kentish Plovers. In flight, Snowy Plovers can be distinguished by their narrow white wing stripe and a partial dark bar at the tip of their tail ( picture).

(Richards, 1988)

  • Range mass
    34 to 58 g
    1.20 to 2.04 oz

Reproduction

In western North America, Snowy Plovers are facultatively polyandrous. Most Snowy Plovers breed in the first nesting season after hatching. Depending on season and location, this varies anywhere between 260-360 days after hatching.

Males solicit females from their territories by calling and standing. The male then runs to a spot in the nest and begins scraping. The female begins scraping as the male steps out, and she settles into the nest. The male bows next to the female several times with his head pointed to the ground. While bowing, he flashes the white on his tail to the female. The female then steps out of the nest to run about 0.5-2.0 m. She stands with her body fairly parallel to the ground. The male then stands directly behind her and begins kicking his legs high. He then jumps on her back. While on her back, he shifts his weight alternately from one leg to the other. Both birds then shift their tails side-to-side with increasing speed. At the moment of intercourse, the male uses his bill to grab the back of the female's neck, and both birds fall backwards with their wings flapping.

The first season of brooding varies geographically. In Puerto Rico, egg-laying begins in January. In Florida, it occurs during the last week of March. In California, egg-laying begins around the beginning of March. Depending on location, the dates of the first clutches range from the middle of March until the middle of May. There may be two or even three brooding seasons, but the last clutch will typically be laid before the middle of July.

Clutch size is normally three eggs. Eggs are laid both during the day and at night. Both sexes take turns sitting or standing over the eggs, and both sexes have a single abdominal incubation patch. Incubation period varies with location and season. On average, the incubation season is 26-32 days.

Small cracks appear up to 8 days before hatching. Tapping of the chicks can be easily heard up to 3-4 days before hatching, and peeping can be heard 1-2 days before hatching. Eggs can hatch at any time of the day or night. Young birds are precocial after hatching.

(Page et al. 1995)

  • Average eggs per season
    3
    AnAge
  • Average time to hatching
    24 days
    AnAge

Lifespan/Longevity

Behavior

Some common observed cleaning behaviors are preening, head scratching, stretching one leg or one wing, and bathing in water.

Snowy Plovers sleep with the bill and the front of the head tucked under their feathers. While sleeping, they will only stand on one leg, especially when the weather is cold. Periodically, they will close their eyes while sleeping.

Both sexes actively defend their nest territories by posturing, chasing, or fighting. This is done by running or flying at the intruder. Males tend to be more aggressive than females. Fights frequently occur between males when their broods are threatened. Adults may sometimes invade another plover's territory to peck their chicks when their own territories are invaded. During some fights, a bird may grab its enemy's tail with their bill and pull on its feathers while turning in circles.

Snowy Plovers are a social bird in winter. Birds form flocks of up to 300 individuals. Nesting birds often gather at small ponds at dusk where they bathe, drink, and feed. Periodic spells of calling and posturing of individual birds within the groups suggest that these nighttime gatherings may be important areas for socialization. During the winter on the Gulf Coast, Snowy Plovers may occur in mixed flocks of other shorebirds, including Piping Plovers.

Both adults brood their chicks, though in western North America, females generally desert their mates and broods about 6 days after hatching. Young birds are normally in the care of either their mother or father until they are anywhere between 29-47 days old, or until they can fly.

When approached by predators, Snowy Plovers will usually run from their nest. They will fly when surprised, though. While running, they may also lower their tail to the ground or flap their wings to feign injury. Snowy Plovers will crouch in their nest when Peregrine Falcons fly overhead. Adults with chicks will react with calls when approached by possible predators, and they will sometimes do this while flying back and forth. Small chicks will usually crouch and remain motionless when approached by predators, whereas older chicks will often run with their parent.

Predators (on adults): Merlin, Peregrine Falcon, Prairie Falcon, Northern Harrier, feral cat, red fox

Predators (on chicks): Loggerhead Shrike, Common Raven, California Gull, American Kestrel, Northern Harrier, Great Blue Heron, crows, Cattle Egret, red fox, opossum, ghost crab

Predators (on eggs): Common Raven, American Crow, Fish Crow, California Gull, Ring-billed Gull, Great Blue Heron, coyote, red fox, gray fox, island fox, striped skunk, spotted skunk, raccoon, opossum, and ghost crab

Communication and Perception

Food Habits

The main foods eaten by Snowy Plovers are terrestrial and aquatic invertebrates. On the Pacific Coast of North America, these include mole crabs, polychaetes, amphipods, sand hoppers, tanadacians, flies, beetles, clams, and ostracods. The foods eaten in San Francisco Bay and in freshwater ponds include flies, beetles, moths, and lepidopteran caterpillars. In saline and alkaline lakes of the Great Basin, Snowy Plovers feed on flies, beetles, hemipterans, and brine shrimp. Sources of food in salt flats of the Great Plains include flies, beetles, grasshoppers, lepidopterans, and beetles. In the Gulf Coast, the bird feeds on small crustaceans, mollusks, marine worms, aquatic insects, and seeds.

Snowy Plovers forage on beaches, tide flats, salt flats, and salt ponds. At beaches, the bird gathers food from sand surfaces, kelp, marine-mammal carcasses, and above and below the average high water line. Birds that are inland search for food on the shores of lakes, reservoirs, ponds, braided river channels, and playas.

When hunting their prey, Snowy Plovers usually pause, look, run, and then seize their prey from the surface of the beach or the tide flat. Above the high-tide line on California beaches, Snowy Plovers search for food at the bases of low growing plants. In Mono Lake, California, Snowy Plovers feed on brine fly larvae (Ephydridae). They often shake the larvae before swallowing them. The birds will sometimes lower their head and charge with their mouth open into a group of adult flies on the ground while snapping their bill. The bill snaps about two to three times to crush the captured flies before swallowing them. This charging method is also used to capture isolated insects on California beaches. Another behavior sometimes used before feeding is to tremble one foot in shallow water or on a wet substrate.

(Page et al. 1995)

Conservation Status

Breeding populations of Snowy Plovers along the Pacific Coast of U.S. and Baja California are listed as threatened by the U.S. Fish and Wildlife Service. Snowy Plovers are also threatened in Oregon, Florida, and Puerto Rico. They are endangered in Washington, and Alabama. They are a species of special concern in California.

On U.S coasts, habitat degradation, caused by recreation and expanding beach-front development, has caused a decline in the size of breeding populations.

Some beaches have been closed in Oregon to protect the Snowy Plovers' breeding grounds. Individual nests in coastal Oregon and Monterey Bay, California, has been fenced in to improve hatching success in those areas. There has been a removal of feral red foxes by U.S. Fish and Wildlife Service in Monterey Bay, California to improve adult and chick survival rates.

(Page et al. 1995)

Other Comments

There are a few subspecies of Charadrius alexendrinus. Charadrius alexandrinus occidentalis are birds on the west coast of South America. C. a. tenuirostris breed on the Gulf Coast (east of Louisiana), Bahama Islands, north coast of the Yucatan Peninsula, Greater and Lesser Antilles, and islands off the north coast of Venezuela. C. a. nivosus are located in the United States and in Mexico. Red-capped Plovers (C. ruficapillus) of Australia and White-fronted Plovers (C. marginatus) of Africa were once thought to be subspecies of the Snowy Plover, but now are regarded as separate species.

(Page et al. 1995)

Contributors

Kelly Tague (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

threatened

The term is used in the 1994 IUCN Red List of Threatened Animals to refer collectively to species categorized as Endangered (E), Vulnerable (V), Rare (R), Indeterminate (I), or Insufficiently Known (K) and in the 1996 IUCN Red List of Threatened Animals to refer collectively to species categorized as Critically Endangered (CR), Endangered (EN), or Vulnerable (VU).

visual

uses sight to communicate

References

Page, G., J. Warriner, J. Warriner, P. Paton. 1995. Snowy Plover. Birds of North America, 154: 1-17.

Paulson, D. 1993. Shorebirds of the Pacific Northwest. Japan: University of Washington Press.

Richards, A. 1988. Shorebirds: A Complet Guide To Their Behavior and Migration. New York City: W.H. Smith Publishers Inc..

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