Western Snowy Plover
Charadrius alexandrinus nivosus
The Western Snowy Plover is one of two Snowy Plover subspecies recognized in North America. The Pacific coast population, C. alexandrinus nivosus, is defined as the population that exists from the coast to 80 km (50 mi) inland. These birds nest on the mainland coast, peninsulas, offshore islands, and in bays, estuaries, or river outlets in Washington, Oregon, California, and Baja California, Mexico. The population is distinct from the one that breeds in the US western interior and it is listed as threatened under the US Endangered Species Act. The west coast population uses 20 Pacific coast breeding sites with the largest in south San Francisco Bay where there are about 500 breeding pairs.
Mother and chick.
Nesting Western Snowy Plover Credit: Courtesy of USGS
SPECIES IN DETAIL
Western Snowy Plover
Charadrius alexandrinus nivosus
CONSERVATION STATUS: Threatened - Protected
CLIMATE CHANGE: Not Applicable
At the Aquarium
The Aquarium’s western snowy plovers live in the Shorebird Sanctuary exhibit outdoors on the second floor.
Geographic Distribution
West coast from Washington to Baja California, Mexico and in some interior western states. Permanent California resident populations.
Habitat
Western Snowy Plovers are found in areas with little or no cover on sandy coastal beaches, salt pans, dry salt ponds, gravel bars, and salt pond levees.
For resting and feeding they need a beach that is wide, flat, and open so they can see potential predators approaching, and one with dunes in the background where they can take cover in extreme high tide conditions and storms.
Physical Characteristics
Plovers are small birds with long, dark or grayish feet and legs, a short dark bill, large eyes, a rounded head, and long, narrow wings that end in a sharp point. These little birds are sand-colored above and white below, with a narrow dark stripe on the forehead and a dark stripe behind the eyes. They have two, small, dark, partial breast bands and dark ear patches. In breeding season the distinctive markings are darker in males than in females. In winter the difference in sexes is less apparent.
Size
One of the smallest plover species, this Snowy Plover subspecies is 15 to 17 cm (5.9-6.6 in) in length and weighs 34 to 58 g (1.2-2.1 oz).Wingspan is 43 cm (17 in).
Diet
These birds feed in the intertidal zone and along the edges of salt marshes, salt ponds, and lagoons. Primarily visual feeders, they use a variety of foraging methods. Among them are a run-stop-peck motion to find and eat crustaceans, worms, and other small marine invertebrates that they find in wet sand and in stranded kelp. In dry areas above high tide, they sometimes pick insects off low-growing vegetation. At the Bolsa Chica Ecological Reserve in Huntington Beach, California, they have been observed in shallow water doing a little “dance” in which they shake and tap a foot to cause a vibration that scares up burrowed prey.
Reproduction
Western Snowy Plovers reach maturity one year after hatching. Nesting season is from early March to late September. They nest on flat open areas with sandy or salty ground where they build the nest in scrapes on bare ground. Males may build several nests that are less than 6 cm (2.3 in) wide before the pair finally occupies one. Clutches range from two to six buff-colored eggs, (average three). Plovers appear to be fairly faithful to breeding sites and often nest on the same sites as Least Terns, (Sterna antillarum). Incubation lasts 25 to 35 days with females usually taking day duty and males doing the incubation at night.
Chicks are born precocial, downy, and ready to leave the nest to find food as soon as their down dries, (about two hours after hatching). Parent birds lead the chicks to food but do not feed them. Females may leave the brood soon after the chicks hatch and nest with another male, leaving original mates to raise the chicks alone for the next month. Chicks fledge in 22 to 31 days.
Behavior
The interior populations of this species are migratory while the coastal populations are both migratory and resident. Most Western Snowy Plovers that breed in California’s Central Valley and the Great Salt Lake migrate to California and Mexican coasts for the winter. During the winter months they rest and eat to build up their fat reserves for the migration to their summer breeding habitats. The California Pacific coast resident population usually congregates on sand spits and dune-backed beaches. In more urban areas they can be found on bluff-backed beaches.
Adult birds use distraction displays such as faking broken wings to lure predators away from nests and chicks. They may lead larger chicks away from predators or use calls to signal the chicks to crouch and hide. Chicks use small clumps of vegetation as cover.
Adaptation
These birds have cryptic coloration. The color of their dorsal areas matches and blends with their surroundings, making them well camouflaged and difficult to see against the sand. They turn away from predators, sometimes crouching to hide their darker head and breast markings. When the birds stop running they seem to disappear, blending into the surroundings.
The egg coloration blends with dry sand or salty barren soil making them almost impossible to see if a parent is not incubating them.
Longevity
The average life span of this subspecies is three years.
Conservation
The US Fish and Wild Life Service defines the Pacific coast population of Western Snowy Plovers as “those individuals that nest beside or near tidal waters and includes all nesting colonies on the mainland coast, peninsulas, offshore islands, adjacent bays, and estuaries from southern Washington to Baja California, Mexico”.
Since 1993 the Pacific coast population (from the coast to 80 km {50 mi} interior) has been listed as threatened under the Endangered Species Act. More recently several petitions to de-list the population have been received (the latest in April 2006); however, after review of the best scientific and commercial information available, the US Fish and Wild Life Service deemed the requests not warranted.
The population decline is largely a result of human activities. Nesting sites are vulnerable to human encroachment, urbanization and disturbance; Predators include crows, ravens, foxes, raccoons, opossums, skunks, American Kestrels, and feral and pet cats. Some nest sites are federally protected.
Special Notes
Western Snowy Plovers have a unique way to catch a meal of kelp or wrack flies. Encountering a mass of the flies on the beach, a plover runs through the cloud of insects with its mouth open, snapping at them to catch them in mid-air.
A public friendly program carried out at UC Santa Barbara’s Coal Oil Point Reserve sandy beach by volunteers has been instrumental in changing the beach from one abandoned by Western Snowy Plovers as a breeding site to one where eggs are now being laid once again. The program has played a vital role in gaining beachgoers’ compliance in avoiding the fenced off habitat areas, providing education, discouraging off-leash dog walking, and scaring away crows trying to steal eggs from the nests. On a beach where only a few years ago almost no beachgoers could identify a Snowy Plover, now beachgoers understand them and how to share the beach with these little shorebirds. Similar programs are taking place at other nesting sites along the California coast.
SPECIES IN DETAIL | Print full entry
Western Snowy Plover
Charadrius alexandrinus nivosus
CONSERVATION STATUS: Threatened - Protected
CLIMATE CHANGE: Not Applicable
The Aquarium’s western snowy plovers live in the Shorebird Sanctuary exhibit outdoors on the second floor.
West coast from Washington to Baja California, Mexico and in some interior western states. Permanent California resident populations.
Western Snowy Plovers are found in areas with little or no cover on sandy coastal beaches, salt pans, dry salt ponds, gravel bars, and salt pond levees.
For resting and feeding they need a beach that is wide, flat, and open so they can see potential predators approaching, and one with dunes in the background where they can take cover in extreme high tide conditions and storms.
Plovers are small birds with long, dark or grayish feet and legs, a short dark bill, large eyes, a rounded head, and long, narrow wings that end in a sharp point. These little birds are sand-colored above and white below, with a narrow dark stripe on the forehead and a dark stripe behind the eyes. They have two, small, dark, partial breast bands and dark ear patches. In breeding season the distinctive markings are darker in males than in females. In winter the difference in sexes is less apparent.
One of the smallest plover species, this Snowy Plover subspecies is 15 to 17 cm (5.9-6.6 in) in length and weighs 34 to 58 g (1.2-2.1 oz).Wingspan is 43 cm (17 in).
These birds feed in the intertidal zone and along the edges of salt marshes, salt ponds, and lagoons. Primarily visual feeders, they use a variety of foraging methods. Among them are a run-stop-peck motion to find and eat crustaceans, worms, and other small marine invertebrates that they find in wet sand and in stranded kelp. In dry areas above high tide, they sometimes pick insects off low-growing vegetation. At the Bolsa Chica Ecological Reserve in Huntington Beach, California, they have been observed in shallow water doing a little “dance” in which they shake and tap a foot to cause a vibration that scares up burrowed prey.
Western Snowy Plovers reach maturity one year after hatching. Nesting season is from early March to late September. They nest on flat open areas with sandy or salty ground where they build the nest in scrapes on bare ground. Males may build several nests that are less than 6 cm (2.3 in) wide before the pair finally occupies one. Clutches range from two to six buff-colored eggs, (average three). Plovers appear to be fairly faithful to breeding sites and often nest on the same sites as Least Terns, (Sterna antillarum). Incubation lasts 25 to 35 days with females usually taking day duty and males doing the incubation at night.
Chicks are born precocial, downy, and ready to leave the nest to find food as soon as their down dries, (about two hours after hatching). Parent birds lead the chicks to food but do not feed them. Females may leave the brood soon after the chicks hatch and nest with another male, leaving original mates to raise the chicks alone for the next month. Chicks fledge in 22 to 31 days.
The interior populations of this species are migratory while the coastal populations are both migratory and resident. Most Western Snowy Plovers that breed in California’s Central Valley and the Great Salt Lake migrate to California and Mexican coasts for the winter. During the winter months they rest and eat to build up their fat reserves for the migration to their summer breeding habitats. The California Pacific coast resident population usually congregates on sand spits and dune-backed beaches. In more urban areas they can be found on bluff-backed beaches.
Adult birds use distraction displays such as faking broken wings to lure predators away from nests and chicks. They may lead larger chicks away from predators or use calls to signal the chicks to crouch and hide. Chicks use small clumps of vegetation as cover.
These birds have cryptic coloration. The color of their dorsal areas matches and blends with their surroundings, making them well camouflaged and difficult to see against the sand. They turn away from predators, sometimes crouching to hide their darker head and breast markings. When the birds stop running they seem to disappear, blending into the surroundings.
The egg coloration blends with dry sand or salty barren soil making them almost impossible to see if a parent is not incubating them.
The average life span of this subspecies is three years.
The US Fish and Wild Life Service defines the Pacific coast population of Western Snowy Plovers as “those individuals that nest beside or near tidal waters and includes all nesting colonies on the mainland coast, peninsulas, offshore islands, adjacent bays, and estuaries from southern Washington to Baja California, Mexico”.
Since 1993 the Pacific coast population (from the coast to 80 km {50 mi} interior) has been listed as threatened under the Endangered Species Act. More recently several petitions to de-list the population have been received (the latest in April 2006); however, after review of the best scientific and commercial information available, the US Fish and Wild Life Service deemed the requests not warranted.
The population decline is largely a result of human activities. Nesting sites are vulnerable to human encroachment, urbanization and disturbance; Predators include crows, ravens, foxes, raccoons, opossums, skunks, American Kestrels, and feral and pet cats. Some nest sites are federally protected.
Western Snowy Plovers have a unique way to catch a meal of kelp or wrack flies. Encountering a mass of the flies on the beach, a plover runs through the cloud of insects with its mouth open, snapping at them to catch them in mid-air.
A public friendly program carried out at UC Santa Barbara’s Coal Oil Point Reserve sandy beach by volunteers has been instrumental in changing the beach from one abandoned by Western Snowy Plovers as a breeding site to one where eggs are now being laid once again. The program has played a vital role in gaining beachgoers’ compliance in avoiding the fenced off habitat areas, providing education, discouraging off-leash dog walking, and scaring away crows trying to steal eggs from the nests. On a beach where only a few years ago almost no beachgoers could identify a Snowy Plover, now beachgoers understand them and how to share the beach with these little shorebirds. Similar programs are taking place at other nesting sites along the California coast.