A small wading bird with long, stilt-like legs and a short, thin, blunt-tipped bill, the semipalmated sandpiper (Calidris pusilla) is fantastically camouflaged with mottled, cryptic plumage (2)(3)(4)(5). During the breeding season, the adult semipalmated sandpiper has rich reddish-brown upperparts marbled with dark brown and black, a white throat and dark brown streaks along the sides (2)(3). At other times of the year, the plumage is much more modestly coloured brownish-grey, with dark centres on the shoulder feathers, a thin, white wing-stripe, white underparts with dark barring on the breast, and a white eye streak (2)(3)(4)(5). The female is typically larger than the male and the juvenile is distinguished by varying amounts of reddish-brown on the shoulders (2)(3)(5). Like other sandpipers, the semipalmated sandpiper has relatively long wings, a long neck and a short tail. The front toes are fairly long and adapted to walking rather than perching, making this bird adept at running on land, as well as wading and swimming when necessary (3)(6).
Proficient at hunting on land, the semipalmated sandpiper typically forages in flocks along the mudflats of shorelines at low tide (3). Prey is spotted visually and pecked at and picked up with the short bill, and includes a variety of arthropods, molluscs and worms (2)(3)(8). It may also wade belly-deep into water where it moves slowly and rapidly probes at underwater burrows in search of prey (3). When prey is in short supply or patchily distributed, the semipalmated sandpiper may defend a feeding territory from other waders with aggressive behaviours including threat displays, chasing and fighting (2)(3). When fighting, competing birds rush at one another with the neck feathers puffed out, the wings half spread and the tail elevated. Such behaviour is most commonly observed during migratory stopovers and at wintering sites, as this is when birds are most tightly spaced (3).
At the start of the breeding season, unpaired territorial male semipalmated sandpipers engage in aerial displays of hovering flights with rapid wingbeats and vocalisations to attract a female mate. Once the female enters the male’s territory, the pair chases each other, often with the tails cocked, wings stretched and the head feathers raised. The male makes a scrape by pressing its breast against the ground and rotating the body, and the female follows the male into this scrape before the pair attempt copulation. Once mated, the female lines the scrape with nesting material, such as small leaves or grass (3). From June through to early July, four to six days after pair formation, a clutch of usually four eggs is laid, and then incubated by both parent birds for 20 to 22 days (2)(3). Shorty after the chicks hatch, the female deserts the nest to begin the southward migration, leaving the male to tend to the chicks alone until they fledge at around 16 to 19 days old. The young birds will first breed at around one year of age and may live for up to 12 years (2).
A highly migratory species, the semipalmated sandpiper breeds in the Arctic regions of North America, before travelling southwards to congregate in Central and South America and, to a lesser degree, the Caribbean and Florida (5)(7)(8). During the winter, most semipalmated sandpipers gather along the coastline of northern South America, particularly in Suriname, French Guiana and north-central Brazil (3).
While breeding, the semipalmated sandpiper builds its nest amongst dry shrubby areas in upland tundra near small ponds, lakes and streams (2)(3)(8). Before migrating, it gathers in areas of shallow fresh or saltwater, along the edges of lakes, on muddy intertidal zones, or on soft silt or clay mudflats. It then travels across the interior of the North American continent, stopping at temporary wetlands to capture a variety of invertebrate prey species (3). At its wintering sites, the semipalmated sandpiper resides on shorelines with mudflats bordered by shallow lagoons and dead mangroves (2)(3)(7).
The semipalmated sandpiper is a hugely abundant bird, with a population estimated at around 3.5 million in the 1990s. This population, however, has been declining since the 1970s at an estimated rate of five percent per year. The primary agent of this is thought to be hunting in its wintering range, where as many as tens of thousands of birds may be shot each year. The semipalmated sandpiper’s ability to cope with such losses is also hindered by the destruction, degradation and pollution of coastal and inland wetlands that the species’ uses during migration. The development of modern agricultural practices has greatly accelerated the loss of these wetlands and, as wetlands are highly dependant on natural precipitation and runoff, climate change is expected to exacerbate their loss over coming years (3).
In light of declining shorebird populations across North America, the Western Hemisphere Shorebird Network was created to identify important seabird sites and help protect them (3)(9). A total of 16 wetland sites have since been identified that are of importance to migratory shorebirds such as the semipalmated sandpiper. In addition, both the Canadian and United States governments have drawn up conservation plans for the preservation of shorebird populations (3).
ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra
A very group of animals that includes crustaceans, insects and arachnids. All arthropods have paired jointed limbs and a hard external skeleton (exoskeleton).
Colouration that makes animals difficult to detect against their background. The colouration may provide camouflage against a background or break up the outline of the body. Both can occur in a single animal, and tend to reduce predation.
To keep eggs warm so that development is possible.
Pertaining to the intertidal zone, the region between the high tide mark and low tide mark.
Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders and corals.
A diverse group of invertebrates, mainly marine, that have one or all of the following; a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.
Describes an animal, a pair of animals or a colony that occupies and defends an area.
An area occupied and defended by an animal, a pair of animals or a colony.
Treeless, grassy plains characteristic of arctic and sub-arctic regions. They are very cold and have little rainfall.
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