Shorebirds: Characteristics, Behavior and Types | Sea Life, Islands and Oceania

SHOREBIRDS

Snowy plover
Shorebirds are like their name says birds that hang out along the edge of oceans or other waterways, generally on mud flats or sandy beaches. Many are waders that have long legs for wading and long bills for picking out and probing prey. Some species have sensory nerve ending at the end of their bills that help them locate prey in the mud or sand. Their wings are built for fast quick getaways rather than gliding and soaring.

Shorebirds are primarily birds of ocean coasts, especially adapted to feeding on tidal flats and marshes, which abound in the small invertebrates they thrive on. At this time of year, however, the newly planted rice paddies, filled with shallow water clear enough to see the bottom, look and function much like tidal flats. Many species of shorebird migrate. Protecting them is difficult because their wintering grounds, breeding grounds and stopover points are all like links in a chain and if one of them fails the whole chain can fall apart.

In coastal areas, shorebirds like to work the edges of waves. They don’t mind getting their feet wet but not their bodies. They often work the beaches in flocks. Some members are always on the lookout for predators. They are often busiest at low tide, when the beach stretches out the furthest. Shorebirds extract large quantities of small mollusks from sandbanks and mud flats when the tide retreats. The animals are extracted from the shells with a flick of the head.

Many shorebirds don’t make nests. They rely on the camouflage coloring of their eggs. Some shorebirds that nest in cliffs lay eggs that are pointed at one end so they roll in a circle rather than rolling off the cliff. Many migrate. Several found in Japan spend their winter months along the coasts of Australia and Melanesia. Their summer breeding grounds are on the tundras of Siberia and even Alaska. Japan is ideally positioned as a stop-over and resting stage on the long journey northward and southward. During their brief stay in Japan shorebirds rely on the abundance of food found in rice paddies to replenish their depleted fat and energy reserves.

In Japan, these migratory shorebirds stay a short time in the countryside, where local rice paddies play a vital role in their conservation. All four species

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; MarineBio marinebio.org/oceans/creatures

Types of Shorebirds

Waders and shorebirds include plovers, snipes and sandpipers. These birds feed on tiny creatures such as crabs, worms and shrimps in shallow water found around the shores of oceans, lakes and rivers. Some have long bills for poking deep in the mud. Others snatch prey on the surface.

Sandpipers and plovers are generally referred to as "shorebirds" in North America and "waders" in Britain. About 200 species have been identified worldwide. Avocets are shorebirds with a characteristic upturned bill. When a member or a pair return to take over incubation duties, the birds exchange a series of "cwit, cwit, cwit" sounds and throw straw at one another.

One of the largest shorebirds is the whimbrel. This is a cosmopolitan species that migrates up and down both sides of the Pacific and Atlantic seaboards. The long bill is down-curved near the tip, ideal for probing deep into mud and even poking down into crab burrows, which are usually dug on a curve. The tip of the bill is fitted with sensitive nerve endings that allow the whimbrel to feel prey that they can't even see.

The ruddy turnstone is a smaller sandpiper with a short, thick bill that flips slightly upward at the tip. These birds, called simply turnstone in Europe and Asia, often search for prey by flipping over stones, leaves and other small objects. Their bill, however, is also well suited to probing in shallow mud. Gray-tailed tattler are medium-size sandpipers with medium-length straight bills. They feed in a probing manner similar to that of the whimbrel, but can be easily identified by their bright yellow legs.

Oystercatchers

Pied oystercatcher
Oystercatcher feed on oysters as their name suggests and other bivalve molluscs such as clams and mussels. Opening a shell for a bird is no easy tasks. Some do it by prying open the shell and cutting the muscle that holds them together (a method called “stabbing”). Other pick holes into shell with their bills and break the shells apart (a method called “hammering”).

American oystercatchers (Haematopus palliates) are wide ranging birds. They can be found in the United States, Cuba, Brazil, and Mexico. They live year-round throughout parts of the Caribbean and the Gulf Coast. In South America, they are distributed as far south as Chile and Argentina. American oystercatchers are commonly found on mudflats, sandy beaches, and occasionally on rocky shores. Nesting habitats include upland dunes, marsh islands, beaches, and dredge spoil islands. During the winter months, they tend to be concentrated in areas with abundant food sources such as reefs, oyster beds, or clam flats. During spring and fall migration, these birds can be found in shellfish beds, sand flats, or intertidal mudflats. [Source: Maddie Hardin, Animal Diversity Web (ADW) /=]

American oystercatchers are relatively large and conspicuous shorebirds. They range in weight from 400 to 700 grams (14 to 25 ounces) and range in length from 40 to 44 centimeters (15.7 to 17.3 inches).Their average wingspan is 81 centimeters (32 inches). Females are larger than males. American oystercatchers are dark brown on the mantle (back) and wings, with black heads and necks. According to Animal Diversity Web: Bright white undersides contrast greatly with these dark upperparts. The narrow white wing patch and white "V" on their upper rump both become visible in flight. Their long, straight, chisel-like bill is red to orange in color, with dark colorings visible toward the end in juveniles. Their legs are long, pale pink, and lack a hallux. Their iris is bright yellow with a visible red orbital eye ring. Their black head and neck, brown mantle, red eye ring, and yellow eyes distinguish this bird from other similar species.

American oystercatchers are listed as a species of least concern in many coastal states. However, because they are rather shy birds, they do not do well with human interaction. They are losing habitat to human disturbance and development along beaches, and to other birds. American oystercatchers tend to avoid nesting near gulls where their nests would be vulnerable to attacks. Market hunting and egg collecting in the 19th Century possibly reduced population numbers in North America.

Oystercatcher Behavior and Feeding

American oystercatchers are migratory and diurnal (active during the daytime). They make loud, recognizable "wheep" or "wee-ah" calls. According to Animal Diversity Web: They are a social species and tend to roost communally in groups containing up to 100 or more individuals. During the day, these birds can be seen running or walking more often than flying. Their normal flight pattern of rapid and deep wing beats becomes softer during courtship displays and when predators are nearby. Much of their daily routine is spent preening, head scratching, sleeping, standing, and sunbathing. Their feeding behavior sets them apart from many other shorebirds. [Source: Maddie Hardin, Animal Diversity Web (ADW) /=]

American oystercatchers feed mainly on marine invertebrates, bivalves, mollusks, worms, clams, crabs and shell fish. They also eat small fish on occasion. Foraging occurs primarily in intertidal areas with a rich diversity of marine invertebrate species. Their long, brightly colored bills help them prey on bivalves and probe for marine invertebrates. Major food items include soft-shell clams, blue mussels, sandworms, razor clams, oysters, and mole crabs. [Source: Maddie Hardin, Animal Diversity Web (ADW) /=]

These birds utilize two distinct feeding techniques, both of which are successful. The first technique is called "stabbing", where a bird walks around an exposed shellfish bed until it spots an open bivalve, which it quickly stabs. After a few quick thrusts from a chisel-like bill, the adducator chain breaks, and the bird can consume the soft parts. This technique is not without risk, as deeply rooted bivalves can clamp down on their bill and hold it down until it drowns in the rising tide. The second feeding technique is called "hammering", in which the bird simply plucks a single mussel from a group of mussels, takes it to a different location, and holds it in its beak in such a way that when it begins hammering, the shell breaks easily and the chain that holds the bivalves together is severed.

American oystercatchers are very vocal, especially during the breeding season, when their breeding display is spectacularly auditory and visual. Their call is loud, rising, and then descending. It is used for a variety of purposes including: greetings between individuals, warning alarms, territorial (defend an area within the home range), disputes, establishing dominance in feeding areas, and begging for food from parents.

Sandpipers

common sandpiper

Sandpipers are a large family of waders known by taxonomic name of , Scolopacidae. They include many species with the name sandpiper as well as those known as curlews and snipes. There around 100 species of these birds. The majority of them eat small invertebrates picked out of the mud, sand or soil. Different lengths of bills enable different species to feed on different kinds of food in the same habitat, particularly on the coast, without direct competition for food. [Source: Wikipedia]

Sandpipers have long bodies and legs, and narrow wings. Most species have a narrow bill, but otherwise their form and length are quite variable. They are small to medium-sized birds, measuring 12 to 66 centimeters (4.7–26.0 inches) in length. The bills are sensitive, allowing the birds to feel the mud and sand as they probe for food. They generally have dull plumage, with well-camouflaged brown, grey, or streaked patterns, although some display brighter colours during the breeding season.

Most species nest in open areas, and defend their territories with aerial displays. The nest itself is a simple scrape in the ground, in which the bird typically lays three or four eggs. The young of most species are precocial (hatched in a fairly advanced state and able to feed themselves and move independently almost immediately)

Common Sandpipers

Common sandpipers (Scientific name: Actitis hypoleucos) can be found throughout the Old World in western Europe, eastern Asia and Africa as well as Australia. During the spring and summer breeding season, they are typically found in the northern hemisphere ranging from the Atlantic Ocean to Japan, usually in temperate climates. Also known as "Eurasian sandpipers" or "summer snipes", common sandpipers are migratory birds that typically winter in warmer climates in Africa, southern Asia, and Australia. Common sandpipers are closely related to spotted sandpipers (Actitis mulcaria) which are commonly found in North and South America. [Source: Ryan Pines, Animal Diversity Web (ADW) /=]

Common sandpipers live in temperate, tropical, terrestrial, saltwater and freshwater habitats. They are found in coastal areas as well as along lakes, ponds, rivers, streams, wetlands, marshes, swamps, bogs, estuaries and areas adjacent to water bodies. These birds can live in a variety of habitats depending on season. During the breeding season, they tend to nest along sandy coasts and river banks preferably near active surf or fast-moving water. Their habitat can extend up into the mountains as high as the tree-line if climate and environment conditions are suitable. They are able to withstand heavy rain and a broad range of day-to-night temperatures that exist in temperate climate. In the winter when the breeding season has passed, common sandpipers tend to move south to more tropical climates where they prefer to live in wetlands. They generally choose ponds, rivers, canals, estuaries, and mangroves. As evidence by their habitat selection, common sandpipers avoid very hot climates, as well as frozen or snowy regions.

Common sandpipers are of the most widespread and adaptable shorebirds, living at elevations from sea level to 4,000 meters (13,125 feet). Their average lifespan in the wild is eight years. Young sandpipers have a survival rate around 57 percent. With adults, this rate rises up to 85 percent. The oldest recorded common sandpiper was 14 years of age. Common sandpipers are designated as a species of least concern on the International Union for Conservation of Nature (IUCN) Red List and have no special status according to the Convention on International Trade in Endangered Species (CITES). There are estimated to be between 2,600,000 and 3,200,000 adults living worldwide. Their population has been declining recently though as a result of recreational fishing and increased human development at coastal areas, which disrupts the breeding activities of many shorebirds. Such disturbances during the breeding season result in failed nesting attempts, and an overall population decrease.

Common Sandpiper Characteristics and Behavior

Common sandpipers range in length from 18 to 24 centimeters (7 to 9.5 inches), with their average length being 20 centimeters (8 inches). Their average weight is 40 grams (1.41 ounces) and their average wingspan is 35 centimeters (13.78 inches). They are endothermic (use their metabolism to generate heat and regulate body temperature independent of the temperatures around them) and homoiothermic (warm-blooded, having a constant body temperature, usually higher than the temperature of their surroundings). There is sexual dimorphism (differences between males and females) in plumage, and females tend to be a little larger than males. [Source: Ryan Pines, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: Adult, breeding common sandpipers are brownish-gray on their heads, napes and breast, which are all faintly streaked with dark brown. Their bellies and undertail coverts are unmarked white. Backs, wings and tails are overall darker brown, mottled with shades of tan and very dark brown. In addition, they often have a white ring around the eyes. Like many migrating birds, common sandpipers molt after the breeding season into their winter plumage. Winter plumage is a more drab version of the breeding plumage, and the streaking in particular fades or disappears completely. The young have white speckles also on the upper part. Juveniles look very similar to wintering adults, but have significantly more buff incorporated into their mottled upperparts. This species can be distinguished from the spotted sandpiper due to their longer tail feathers and darker legs. They are approximately eight grams at hatching and their mass increases to about 40 grams when able to fly. In addition they grow to be about 20 centimeters long with bills measuring 21 millimeters in length.

Western sandpipers

Common sandpipers are diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), migratory (make seasonal movements between regions, such as between breeding and wintering grounds), territorial (defend an area within the home range), and social (associates with others of its species; forms social groups). They live and migrate in groups of about 30. Although males defend territory and mates, specific territory size is not known. [Source: Ryan Pines, Animal Diversity Web (ADW) /=]

Common sandpipers forage, preen and bathe during the day. They are often identified by their characteristic bobbing head and tail when walking along the ground, which appears to resemble a nervous tick that is referred to as "teetering". These birds are also well known for making long distance migrations each year. During the spring and autumn, they generally travel to places with warmer climates. Adults migrate along the coast, while juveniles do so more inland. They fly close to the ground or water and emit a distinct three note call particularly when in the air. Their flight can be easily recognized due to their stiff, bowed wings.

Common sandpipers sense using vision, touch, sound and chemicals usually detected with smell and communicate with vision and sound, in particular the communicate with each other with vocalizations that resemble "Twee, wee, wee". These vocalizations are most common when they are flying in the air. Common sandpipers are noisy when breeding or moving, but are very quiet when eating. In addition, they may use their wings for visual signaling.

Common Sandpiper Feeding and Predators

Common sandpipers usually eat small invertebrates, crustaceans, aquatic and terrestrial insects, worms, and spiders, as well as scavenge scraps from boats or from near shore sources. On occasion, they eat small amphibians, tadpoles, fish and seeds. They locate live prey by running along the coastline and then run, swim, or dive to capture it. They break their prey into smaller pieces in order to feed. Typically, they feed individually or in pairs and avoid foraging in areas where other flocks feed to avoid competition and predation. [Source: Ryan Pines, Animal Diversity Web (ADW) /=]

Young common sandpipers are particularly vulnerable to predation before fledging. Further enhancing their vulnerability, chicks tend to be weak and unable to escape predators. As a defense against predation, parents fly away in order to distract the predators and they gather in flocks to work together to provide defense. When near water, they can also dive for short periods of time when being chased. Like many sandpipers, their brown-mottled coloration serves as camouflage in their coastal habitats. Their main known predators areestuarine crocodiles, foxes, weasels, gulls and skuas. /=\

Common Reproduction, Nesting and Young

Common sandpipers engage in seasonal breeding. They breed once a year, typically during May and June. The number of eggs laid each season ranges from three to four, with a per season average of 4.The average time to hatching is 21 days, with the fledging age ranging from 22 to 28 days. Young are precocial. This means they are relatively well-developed when born. Parental care is provided by both females and males. During the pre-fertilization, pre-birth stage and pre-weaning stages provisioning and protecting are done by females and males. On average males and females reach sexual maturity at age two years.

Common sandpipers are almost exclusively monogamous for each breeding season. The length of this pair bond is currently unknown. The male will defend his territory and his female by making threatening displays. A specific example is a salute where they throw out one or both wings as a warning that they are prepared to chase intruders off to defend the territory. On rare occasions, the female may join in displaying threats, but the female does not engage in fighting. The female is responsible for building the nest. Once the eggs have been laid, both parents share incubation duties until the eggs hatch after three weeks. The young are fed and protected by both parents for several days after hatching. Young are able to leave the nest soon after hatching to hide in nearby vegetation. The female typically departs before the young fledge.

Common sandpipers construct scrape nests, which are essentially shallow indentations on the ground and are typically left unlined. The female excavates a nest within 50 meters of water. The chicks usually hatch within the first 10 days of June. The growth rate of chicks have been shown to correlate with weather, with higher growth rates associated with warmer temperatures. Under these conditions they tend to grow up fact, but expend a lot of energy early on in development. Juvenile common sandpipers often remain in the wintering grounds for their first summer, and thus don't breed until almost two years of age. /=\

sanderlings on the beach

Sanderlings

Sanderlings (Scientific name: Calidris alba) are the small, plump sandpipers that race back and forth on the shoreline, just in front of incoming waves. They are extremely fleet footed for birds. They hang out in small flocks and snatch small crustaceans and insects in the sand. "As each wave swills back, they follow it, probing and pecking at any morsel that has become stranded and then as next wavelet floods in, they run back again to the shore." They often fight among themselves. If they are disturbed they make a "twick, twick" noises and quickly fly out over the sea until the threat is gone. Sanderlings are very tame and people can get quite close to them before they fly off. They migrate between southern areas in the winter and northern areas in the summer. Sanderlings and other kinds of sandpiper are are often found together. Sanderlings can be distinguished from other sandpipers by their whiter appearance in the autumn.

Sanderlings are found at beaches and along coastlines of all the world's oceans and seas from about 50̊ north longitude in the Northern Hemisphere summer to about 50̊ south in winter, including both temperate and tropical coastal areas. They have one of the widest winter ranges of any shorebird. Their winter range in the Americas includes Pacific coastal areas as far north as British Columbia and as far south as northern Chile and Atlantic coastal areas as far north as southern Maine and as far south as Brazil. They are also found throughout the coastlines of the Great Lakes, Gulf of Mexico and the Caribbean Sea. Winter range outside of the Americas is from the British Isles to the Mediterranean Sea, Caspian Sea and throughout southeast Asia to South Africa, Australia, and many South Pacific islands. In the breeding season they are found in high arctic areas of Greenland, Scandinavia, Russia, Siberia, and Canada. [Source: Tanya Dewey, Animal Diversity Web (ADW) /=]

Sanderlings live in temperate, tropical land and saltwater- marine environments and in tundras, deserts and dune areas. They are typically found in coastal areas and have distinct habitats in the breeding and winter seasons. In winter they are mainly found along sandy beaches, where they probe for food ahead of and behind waves in the active surf zone. They may also forage in mudflats, lagoons, and rocky intertidal areas. They are most common along ocean coasts, but are also found on sandy beaches of inland lakes, prairie potholes, and saline or alkaline flats. In the breeding season, sanderlings are found in the high arctic tundra, where they nest in a variety of habitats, but mainly rocky ridges or slopes near moist tundra or ponds.

Historically sanderlings were considered a game species and were hunted for food and market sales. Arctic natives collected eggs to eat. Today their populations are relatively stable and healthy. The International Union for Conservation of Nature (IUCN) Red List classifies them as a species of “Least Concern”. They protected under the U.S. Migratory Bird Act. They have no special status according to the Convention on the International Trade in Endangered Species (CITES). Even so, their breeding habitats in the Arctic tundra are threatened by global climate changes. Their wintering habitats are threatened by oil spills, beach and wetland development. Sanderlings rely on the timing of seasonally abundant prey during migratory stopovers, such as the breeding of horseshoe crabs on the Atlantic coast of North America. Sanderlings feed on horseshoe crab eggs at a critical point in their migration and the loss of this resource may impact survival during migration and breeding success. Sanderlings leave areas with heavy human or vehicle use of beaches. The longest recorded lifespan in a sanderling is 13 years. Adult survival is estimated at 83 percent yearly. Most natural mortality can be attributed to predation and cold stress on young.

Sanderling Characteristics, Feeding and Predators

Sanderlings are small sandpipers with black legs and feet and a stout, short, black beak. They range in weight from 40 to 100 grams (1.4 to 3.5 ounces) and range in length from 18 to 20 centimeters (7 to 8 inches). Both sexes are roughly equal in size and look similar. In their non-breeding plumage they have a very pale, whitish head, with pale gray upperparts and white underparts. In all plumages they have a dark shoulder patch that extends onto the throat and breast.[Source: Tanya Dewey, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: In flight they have a white wing stripe that is bordered by black. In their breeding plumage the upperparts take on a reddish brown color and the head becomes more deeply colored. Juveniles are similar to adults, but have darker plumage on the upperparts. Females and males are similar, although males tend to be slightly more colorful. They are easily confused with other, similarly-sized sandpipers, but their black bill, pale head, and their sandy, coastal habits help to differentiate them. Birds in breeding plumage may be confused with red-necked stints (Calidris ruficollis), except that these birds lack any dark markings that extend on the neck and chest. Sanderlings also lack a hind toe, helping to distinguish them from other sandpipers, but this is difficult to discern in the field. /=\

sanderling

Sanderlings eat aquatic and terrestrial invertebrates that are found in their preferred, sandy or tundra open habitats. Examples of important winter and migratory prey are sand crabs, isopods, and horseshoe crab eggs along the Atlantic coast. They occasionally take plant seeds, buds, roots, and shoots when animal prey is not available. Sanderlings feed by probing with their bills or picking things off the ground. They run just ahead of and behind waves on beaches, probing the soft sand for prey as they go. In the breeding season, along pond or stream edges in the tundra, insects are the primary prey, including especially craneflies, midges, and mosquitoes. During winter and migration, when most sanderlings are found along coastlines, they eat mainly small crustaceans, bivalves, polychaete worms, insects, and talitrid amphipods. /=\

Their main known predators are parasitic jaegers (predator birds), long-tailed jaegers, glaucous gulls, snowy owls, wolves. arctic foxes, merlins, peregrine falcons, cinereous harriers, burowing owls, short-eared owls, Sechuran foxes, laughing gulls, house rats and domestic cats. When threatened by predators, sanderlings that are on a nest may crouch on the nest, flattened out, or run a short distance and then crouch on the ground, as if protecting a nest. They may also pretend to be injured or mob jaegers in groups. When young are hatched, parents alert young of danger with a sharp call, which causes them to freeze. The camouflage coloration of sanderlings helps to protect them against predation. In their arctic breeding areas, most predation is on eggs and young. /=\

Sanderling Behavior and Communication

Sanderlings are terricolous (live on the ground), diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), migratory (make seasonal movements between regions, such as between breeding and wintering grounds), territorial (defend an area within the home range), and social (associates with others of its species; forms social groups). In terms of home range, sanderling space use and degree of territoriality varies substantially throughout their range. In winter, non-breeding season, most individuals are found in flocks, although some individuals will defend foraging territories. Both sexes and all ages may be territorial and the strength of the territorial response to an intruder varies as well. In some areas, territoriality seems to be a characteristic of migrating individuals and not over-wintering individuals. The degree of territoriality in a local population may also depend on the availability and abundance of prey and the presence or absence of avian predators.

Sanderlings migrate northwards from March to June and southwards from July to October. Adults and juveniles are not segregated on wintering grounds and don't migrate separately. Populations do not seem to have established migration routes and there seems to be much mixing among populations over large distances. However, most migration occurs along coastlines and similar suitable habitats. The average migration distance is 77 degrees of latitude. /=\

Sanderlings are found in tightly packed flocks during most of the year. Flocks can be just a handful of individuals to over 80. They flock with other shorebirds during winter and migration. They roost together on the ground and in the open, individuals are packed relatively tightly together when roosting. They can run very quickly, something that is especially noticeable when they are following crashing waves up and down the surf zone. Flocks take flight when disturbed and fly quickly to a nearby area of shore to continue foraging. Sanderlings spend much of their time foraging, from 40 to 85 percent of their daily budget. /=\

Sanderlings sense using vision, touch, sound and chemicals usually detected with smell and communicate with vision and sound. They use visual displays and calls during courtship and breeding. Outside of the breeding season they are relatively quiet. It is not thought that they learn calls. Chicks give a chirp when startled that will cause their nestmates to run away, this chirp is similar to the sound used by adults to alert others of a predator ("chidik"). Adults also use a call to tell their hatchlings that the danger has passed. Various other calls are used when departing from the nest, in aggressive interactions, and during displays and copulation. /=\

Sanderling Mating, Nesting and Young

Sanderlings engage in seasonal breeding. The breeding season is from late May through July or early August each year. Sanderlings lay one to two clutches each breeding season, with the average number of eggs per season being four. The time to hatching ranges from 23 to 32 days, with the fledging age ranging from 12 to 14 days and the age in which they become independent ranging from 17 to 21 days. On average males and females reach sexual maturity at age two years.

Mating systems in sanderlings are exceptionally flexible. They can be monogamous (have one mate at a time), polyandrous (with females mating with several males during one breeding season) and polygynous (males having more than one female as a mate at one time). Methods can vary regionally and from year to year, depending on conditions. According to Animal Diversity Web: Flexibility in mating systems may be a way of responding to the unpredictability of resources in breeding habitats. However, some studies suggest regional differences in mating strategies may be fixed.

Pair bonds are typically formed soon after sanderlings have arrived on the breeding grounds, generally in late May and early June. Males, and sometimes females, perform elaborate displays accompanied by vocalizations. Sometimes multiple birds display together. The display flight is described as a flight at two to 10 meters high with the body parallel to the ground and the head held down. Birds move their heads from side to side as they fly and rapidly flutter their wings, followed by a brief glide. The result resembles a fluttering hover and can last up to two minutes. This display flight is accompanied by a song. Once a pair bond is formed, the male uses a jerky walk and calls to the female, who calls back. Males and females are inseparable at this time. In some populations one or the other mate will abandon its partner soon after incubation starts. /=\

Females choose a nest site in the breeding area and construct a scrape on the ground in an open area and may line it with leaves and lichens. Egg-laying occurs in late June or early July. Females lay four greenish, brown spotted eggs, usually at intervals of about one per day. They begin to incubate when all eggs are laid. Females lay one to two, rarely three clutches, depending on the region and local conditions. If a female lays two clutches, her male mate remains with the first brood and the female rears the second brood.

During the pre-fertilization stage provisioning and protecting is done by females. During the pre-birth stage provisioning is done by females and protecting is done by males and females. Pre-weaning and pre-independence protection are provided by males and females. Both parents incubate, brood, and protect the young. In areas or years when females can lay a second, or even third, clutch, they will abandon their male mate with the first clutches and then care for the final clutch on their own. Young are brooded and protected by the parents until a few days after they fledge.

Once the eggs hatch, the parents carry the eggshells away from the nest and begin to brood the young. Young are precocial. This means they are relatively well-developed when born. Soon after hatching they can walk and feed themselves. One day after hatching parents lead young away from he nest. Sanderlings breed in the second year after they hatch. Yearlings don't typically arrive on breeding grounds early enough to start breeding./=\

Plovers

Pacific golden plover

Plovers are shorebirds that generally have shorter bills than sandpipers, and locate their prey visually rather than by probing with their bill. Pacific golden plovers (Scientific name: Pluvialis fulva) are one of the better known and more numerous plover species. They are thick-bodied, powerful birds. They have drab plumage in the winter and molt into magnificent black, gold and white feathers for the summer.

Pacific golden plovers nest along the Arctic Ocean in Siberia, from the Yamal Peninsula to the Bering Sea, and along the Bering Sea and Chukchi Sea in western Alaska. Wintering regions vary with breeding regions. The Alaskan population winter in the South Pacific and Hawaii. The east Russian population winters in the South Pacific, Australia, and Southeast Asia. The central Russian population winters in southern Asia and northeast Africa. [Source: Joseph Miller, Animal Diversity Web (ADW) /=]

Pacific golden plovers are typically found in coastal areas as well as urban, suburban and agricultural areas at elevations from sea level to 500 meters (1640.42 feet). They nest on dry-to-moist open tundra among lichen covered rocks. The vegetation consists of grasses and sedges. Over the winter they live along ocean coasts and prefer a variety of open spaces such as agricultural fields, beaches, coastal marshes, mudflats, airport fields, and golf courses.

Pacific golden plovers nest in extremely remote locations sparsely populated by humans. This allows them to rarely come into contact with humans there. During the winter however, they migrate to highly populated areas like southern Asia, East Asia, and Hawaii. They frequently are found on lawns, golf courses, and airport runways. Collisions with airplanes are common in Hawaii. The International Union for Conservation of Nature (IUCN) Red List classifies them as a species of “Least Concern”. They are protected under the U.S. Migratory Bird Act. They have no special status according to the Convention on the International Trade in Endangered Species (CITES). In the Western Hemisphere, Australia, and New Zealand the Pacific golden plover is protected by law from hunting. However, in Southeast Asia commercial harvesting is widespread. Current estimates for their population size is around 190,000 to 250,000 individuals and populations are believed to be shrinking.

The longevity record for the Pacific golden plover is 21 years and three months. Records on the Seward Peninsula indicate males nested for at least 10 years and females eight years. Survival rates on Oahu vary from 89 percent to 96 percent. Extreme weather and predation are the most common ways in which Pacific golden plovers are killed. They are occasionally killed by hunting, collisions with man made structures, and poisoning.

Pacific Golden Plover Characteristics

Pacific golden plovers are a mid-sized plovers. They range in weight from 108 to 228 grams (3.8 to 8 ounces) and range in length from 23 to 26 centimeters (9 to 10 inches). Their average wingspan is 44 centimeters (17.3 inches). Their average basal metabolic rate is 1.85 cubic centimeters of oxygen per gram per hour. Both sexes are roughly equal in size and look similar. Sexes are colored or patterned a differently. Bills are black and irises are dark brown for all sexes and ages, legs and feet are gray to black depending on age.[Source: Joseph Miller, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web (ADW): Pacific golden plovers hatch with natal down that is overall yellow with black/brown mottling. The underside is mainly gray. They then develop the juvenile plumage. The juvenile plumage is similar to the definitive basic plumage. The head is light brown with black, white, and yellow mottling. The feathers are dark to light brown with yellow edges and spots. The chest and flanks are brown/white and the underside is white. The formative plumage, or first basic plumage, is similar to the definitive basic plumage and juvenile feathers are being worn and lost. Once juvenile feathers are lost they look mostly like the definitive basic plumage. The first alternate plumage does not appear in all individuals. This plumage is highly variable and sexing and aging is hard when they are near this stage. Once they reach their second fall the Pacific golden plovers begin their definitive basic plumage. The head is a light brown with mottling of white, black, and yellow. The chest is brown/white and light brown mottling. The wings are a darker brown with black, white, and yellow mottling. The wing tips get darker the farther out they are and the underside is a light brown/white.

Pacific golden plovers in flight

The sexes are very similar except for 80 percent dimorphic with the outer retrices of males having dark gray/white or black/white bars and females with less defined coloration. The definitive basic plumage lasts from October to March. From April to September the Pacific golden plover changes to its definitive alternate plumage. The definitive alternate plumage is the best time to tell sexes apart. The males develop a strong black underside coming up the chest and the chin and ending in the auriculars. Then there's a white stripe starting on the forehead and going around the auriculars and down the flanks. The backside, crown, nape, and wings of males is a bright golden with black and a little white mottling. The females have the black underside and chest but stops before the throat and has some white mottling. Females do not have the strong defined separation of color seen in males and the white stripe is blended into the wings and the underside. The backside, crown, nape, and wings has the bright golden with black and white mottling. /=\

The Pacific golden plover is a sister species with the American golden plover. The two can be almost indistinguishable. The main differences between the two species are Pacific golden plovers are shorter (23-26 centimeters) than American golden plovers (24-28 centimeters) and the flattened wing of the Pacific golden plover is generally less than 175 millimeters whereas the American golden plover is generally greater than 180 millimeters. Also in the definitive alternate plumage the Pacific golden plover has brighter golden markings on the backside than the American golden plover. /=\

Pacific Golden Plover Behavior

Pacific golden plovers are terricolous (live on the ground), diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), migratory (make seasonal movements between regions, such as between breeding and wintering grounds), and social (associates with others of its species; forms social groups). The size of a nesting pair’s range territory is 10 hectares to 50 hectares. They forage mostly within the territory but extraterritorial foraging is common and communal foraging spots have been observed. /=[Source: Joseph Miller, Animal Diversity Web (ADW) /=]

Pacific golden plovers are highly territorial (defend an area within the home range), during the breeding season. According to Animal Diversity Web: Pairs defend their territory with ground and aerial displays, vocalizations, chases, and fights. Displays are most intense near the center around the nest. Aggressive behavior such as chases and aerial displays occasionally leads to fighting. On the ground the birds will try to peck the other in the wings, head, and feet. Repeated series of chases, displays, and fights are common. Territories on wintering grounds are much smaller (0.4-0.5 ha) and some birds don't have any territory at all. Wintering territories are held by both sexes but predominantly male and they are held for the entire season. The birds will often reclaim the identical territory they had from the year before. /=\

To travel short distances Pacific golden plovers stay almost exclusively on the ground. They run or walk on the ground and rarely use elevated perches. They are capable of long distance flight to and from wintering grounds over vast open ocean. They are not aquatic birds and so seeing them floating on open water is rare. The only times they have been seen floating are in poor visibility or if they're injured. /=\

Pacific golden plovers stay mostly to themselves and their pairs. They are known to be occasionally social on extraterritorial foraging areas. Most other species are not tolerated with the exception of the dunlin. Flocking is common during the migration and directly prior to migration. During the winter, territorial birds will become violent towards other individuals who encroach on their territory.Nonterritorial individuals forage together but maintain regular inter-individual spacing. Most birds will congregate at communal roosts at nighttime. /=\

Pacific golden plovers communicate with vision and sound and sense using vision, touch, sound and chemicals usually detected with smell. There are nine different known calls that the Pacific golden plover has. There are distinct differences between breeding season vocalization and winter vocalization. First are the breeding season vocalizations. The repetitive call is a type of song sung during a breeding display for around 15-40/min. The complex whistle is another song that follows the breeding display with the repetitive call. The female echoes the call after the male. The alarm/distraction call is used to alert other birds and both sexes are similar. The aggression call is similar to the alarm/distraction but more chattery. The courtship call is a call males perform that consists of soft trills and bursts. The intrapair calls are subtle calls used in intrapair communication. The following are the winter vocalizations. The flight calls vary considerably and can be up to 20 different calls. Most are whistles of different syllables. The alarm calls are to alarm other birds and are drawn out and sharp sounds. The aggression calls are melodious and used in territorial (defend an area within the home range), disputes and birds at nocturnal (active at night), roosts.

Pacific Golden Plover Feeding and Predators

Pacific golden plovers forage primarily on land on flat and open expanses. This includes tundra, beaches, fields, and urban areas. They are omnivorous and their diet mainly consists of terrestrial invertebrates, seeds, and berries. Regional reports have Pacific golden plovers eating a highly variable diet including insects, mollusks, seeds, berries, fish, small reptiles, small mammals, flowers, leaves, and sometimes small bird eggs. Some common animals Pacific golden plovers are known to eat are: crane flies (Tupilidae), earthworms (Lumbricidae), and brine shrimp (Artemia franciscana). [Source: Joseph Miller, Animal Diversity Web (ADW) /=]\

When Pacific golden plovers forage they run, stop, scan the ground, and peck. Prey is captured by their bill with one peck or several. Sometimes they have to probe the soil and bury their bill and face in order to capture prey. They rely mainly on their vision instead of other senses like smell or hearing to find prey. Birds that are foraging for berries peck at bushes and shrubs at eye level sometimes finding spiders and insects as well. /=\

Pacific golden plovers are not known to forage cooperatively but foraging during incubation depends on duties. The one not incubating forages alone while the other incubates. Mates that have not mated yet or already have young forage together. Feeding mostly occurs during daylight and only in a few confirmed locations do they feed at night.

Pacific golden plovers are prey to a wide variety of raptors and mammals. Their main known predators are rough legged hawks, Hawaiian hawks, peregrine falcons, short-eared owls, pomarine jaegers, mongooses and Arctic foxes. In their tundra breeding grounds they are preyed upon by raptors and Arctic foxes that traget for younger and smaller birds. Pacific golden plovers call to one another when they spot a predator. They are well camouflages in the tundra breeding grounds. Their colors and patterns blend in with the ground and tundra vegetation. The birds nest nest on the ground. If a predator approaches they remain motionless until the last second and then make an escape or don’t move until the danger has passed. An unconfirmed observation has a Pacific golden plovers attempting to outclimb a predator. /=\

Pacific Golden Plover Mating, Nesting and Offspring

Pacific golden plovers engage in seasonal breeding. They breed once yearly. The breeding season is during the summer. Pairing begins at the earliest in late April and nesting ends at the latest in early August. The number of eggs laid each season ranges from three to five. The average time to hatching is 25 days, with the fledging age ranging from 26 to 28 days and the age in which they become independent ranging from 26 to 28 days.On average males and females reach sexual maturity at age one year [Source: Joseph Miller, Animal Diversity Web (ADW) /=]

Pacific golden plovers are monogamous, which means they have only one mate per breeding season. Most pairs do not remain together for more than one breeding season but multi-season pairings are known to occur. According to Animal Diversity Web: Some Pacific golden plovers arrive to breeding sites already paired but most find their mates after the migration, on the breeding sites. Individuals that pair before migration are possibly wintering territorial neighbors and the female follows the male to his nesting territory. Most are paired when a female settles on another male's territory. Most pairs are apparent within 3-6 days of migration arrival. A territorial display done by males, called the butterfly display, may serve as an advertisement to females. These displays usually begin on the first day after arrival. They last throughout the breeding season to defend their nest. /=\

Parental care is provided by both females and males. Pre-fertilization protection is provided by males. Pre-birth, pre-weaning and pre-independence protection are provided by males and females. When Pacific golden plovers reach sexual maturity at around afe one they still have their juvenile plumage and mating may often does not occur until the next breeding season, but it does sometimes happen. When an individual does find a mate, they pair in the spring or early summer. Copulation occurs shortly after pairing and a nest is

Male Pacific golden plovers find possible nest sites and scrape them clear of lichen and construct the final nest lined with lichens, leaves, and grasses. Before hatching, both the males and females incubate the eggs. The males that are not incubating defend their nest by aerial displays and will forage within earshot. Males also defend nests from predators and competitors nearby. /=\

Young are precocial. This means they are relatively well-developed when they hatch. made. The earliest chicks hatch in May, and at the latest hatch in August. Birth weight varies with environment and parents but it is usually around 17 grams. The chicks feed on their own. Parents protect them until they are able to fly. Time to fledging is around 26-28 days. After hatching, brooding takes place for a few hours and afterward the chicks leave the nest. Parents do not feed their young, so they forage by themselves with the protection of their parents. Both parents remain with the chicks through most of the chick stage. Females are usually the first to abandon the young. This usually takes place soon after they learn to fly. Males then abandon them to join the southward migration, leaving the juveniles alone for the first time in their lives. Juveniles are the last to fly south from August to October.

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated May 2023