The Pectoral Sandpiper is a medium-sized sandpiper that breeds on wet tundra in both the North American and Siberian Arctic and winters mostly in southern South America. Breeding males have an inflatable throat sac, which expands and contracts rhythmically during display flights. The accompanying vocalization consists of a series of hollow hoots, and is one of the most unusual sounds heard in summer on arctic tundra. Correlated with this unique display is a noticeable degree of sexual dimorphism and a polygynous or promiscuous mating system, characteristics that set this species apart from most other calidridine sandpipers.
Pectoral Sandpipers migrate southward from arctic breeding areas in largest numbers through central North America to winter primarily on the pampas of south-central and southern South America. Most individuals that breed in Siberia migrate east, or perhaps even along the Great Circle route over the Arctic Ocean, to Alaska or Canada and then on to South American wintering areas. Individuals at the extremes of this range potentially make a total return-trip migration of more than 30,000 km, a distance comparable to that flown by the Arctic Tern (Sterna paradisaea) and other migratory champions. Small numbers winter regularly in Southeast Asia and the South Pacific (mainly Australia and New Zealand). Northward migration proceeds rapidly through central South America and the Caribbean, concentrating in the central United States and Canada, to arctic breeding areas in both North America and Siberia.
A century or more ago the species was reported to occur in "enormous" numbers along migratory pathways, but there are no comparable data to establish if current numbers are reduced as compared to historic levels. It is generally believed that long-term population reduction, if it has occurred, was because of market hunting in the late nineteenth century, but more likely because of more recent habitat loss and degradation. Recent surveys conducted on the breeding grounds show that the species is more abundant than was previously believed. Population numbers have been stable over recent history.
Many aspects of Pectoral Sandpiper breeding and migration biology have been studied, providing a reasonably good outline of its distribution, ecology, and life history. Little information exists, however, on the distribution and ecology of populations in the nonbreeding season, where birds spend half the year. Moreover, most studies to date have been conducted on a small-scale, study site basis, without a formal means of supporting a larger, landscape perspective. There is a need to begin conducting range-wide syntheses, the results of which are needed to identify information that is most critical to conservation.