Upland Sandpiper

Birds arrive on their breeding grounds in late April to early May, often already paired. Nest preparation begins approximately two weeks after arrival. Both sexes help construct the nest — the male initiates the scrape and the female completes it and adds the lining. Nests are shallow scrapes on the ground, typically 10–13 cm in diameter and 4–7 cm deep, lined with dry grasses, leaves, and small twigs. Surrounding vegetation is often arched over the top to conceal the nest from above.

The clutch typically consists of 4 eggs (range 2–7), creamy to pinkish-buff in ground colour and evenly spotted with reddish-brown. Eggs measure approximately 45 × 32.5 mm. Both parents share incubation duties over 21–29 days, averaging 24 days in the Great Plains, starting with the last egg laid. Only one brood is raised per season, and age at first breeding is one year.

Chicks are precocial and downy at hatching, leaving the nest within 24 hours and feeding themselves within a few days. Both parents perform distraction displays to lure predators away from the brood. In most cases, adults remain with the young for about one week after hatching, after which the female typically departs for the wintering grounds before the male. Juveniles take short flights at around 18 days and are fully fledged at approximately 30–31 days.

The mating system is more complex than simple monogamy. Studies have found evidence of two females laying eggs in a single nest, and of multiple males fathering eggs within a single brood — suggesting occasional polygamy and extra-pair fertilisation. Nesting can be loosely colonial, with pairs in a local area often synchronising their nesting stages. Pairs show strong site fidelity, returning to the same area year after year.

In 2019, a bird banded as a chick on the Konza Prairie Biological Station in Kansas in 2006 was photographed alive on a fence post barely a mile from its banding site — 13 years and 1 month after banding, and a new species longevity record. The typical lifespan in the wild falls between 5 and 8 years, making that individual a genuine outlier.

Survival rates are influenced by the hazards of long-distance migration — non-stop transoceanic flights of up to 7 days leave little margin for error — as well as predation on the breeding grounds, nest failure from agricultural disturbance, and conditions on the South American wintering grounds. Pesticide use on the pampas may be suppressing survival rates in ways that are difficult to measure from North American monitoring alone.

Compared to other members of the family Scolopacidae, the Upland Sandpiper's lifespan is broadly typical. The Wood Sandpiper has a recorded maximum of around 11.7 years, while larger shorebirds such as the Bar-tailed Godwit have been recorded living beyond 30 years. Strong site fidelity — returning to the same field year after year — means long-lived individuals can be reliably monitored, making longevity records more likely to be detected than in more nomadic species.

The Upland Sandpiper is listed as Least Concern on the IUCN Red List (2021), with a global population estimated at 750,000 mature individuals by BirdLife International and Partners in Flight. The global population trend is currently assessed as increasing. The North American Breeding Bird Survey found the population was broadly stable between 1966 and 2015, with a moderate increase in the final decade of that period. The species scores 11 out of 20 on the Partners in Flight Continental Concern Score, indicating low overall conservation concern at the global level.

Regional patterns tell a more complicated story. In the northeastern United States, populations have declined sharply and the species is now listed as endangered in Pennsylvania and Connecticut, threatened in New York, and is a species of conservation concern in nearly two dozen US states and Canadian provinces.

The conversion of native prairies and grasslands to cropland is the primary long-term threat. Pesticide use reduces insect prey availability; early haying destroys active nests; intensive row-cropping eliminates suitable habitat entirely.

The species has a dark history with market hunting. In the late 19th century, tens of thousands were shot annually in Midwestern states and sold at eastern markets — particularly after the decline of the Passenger Pigeon left hunters seeking a new quarry. The Migratory Bird Treaty Act of 1918 ended commercial hunting in the US and Canada, allowing populations to partially recover. On the South American wintering grounds, hunting and insecticide use continue to suppress numbers in ways that are difficult to quantify.

Climate change poses an emerging threat: spring heat waves endanger chicks in the nest, and range shifts are projected as grassland conditions change. Controlled burns benefit the species by creating short-grass conditions and concentrating grasshopper prey. Conservation management at airports — where the species now nests in several northeastern states — has become an unlikely but important tool for maintaining local populations.

A male Upland Sandpiper at the peak of display climbs to 305 m above the prairie, circling and delivering the wolf whistle for up to 15 minutes before folding its wings and plummeting back to earth. These aerial song-flights occur throughout the day and into the evening during the breeding season, and the calls carry for considerable distances across open grassland.

On the ground, the male approaches the female with the body lowered, the long tail cocked upward, and the throat inflated, producing a staccato rattle while running toward her. Both sexes give the wolf whistle during courtship, and pairs can be seen calling from fence posts and telephone poles in a kind of duet before nesting begins.

The mating system appears more complex than simple monogamy. Studies have documented two females laying eggs in a single nest, and genetic analysis has revealed multiple males fathering eggs within a single brood — evidence of both egg dumping and extra-pair fertilisation. Nesting is sometimes loosely colonial, with pairs in a local area synchronising their nesting stages, which may facilitate these more complex reproductive arrangements.

Pairs show strong site fidelity, returning to the same territory year after year. This consistency means that established pairs likely reunite on the breeding grounds rather than forming new bonds each season, though this has not been confirmed by long-term individual tracking studies.

Every September and October, hundreds of Upland Sandpipers descend on the Ozogoche Lakes in the high Andes of Ecuador — a cluster of glacial lakes at around 3,300 m elevation — and plunge into the icy water, dying of hypothermia. The event, known locally as the "jamiñawin" ("closing of the eyes"), has been documented for generations and draws visitors from across Ecuador. Scientific explanations remain contested: theories include disorientation from volcanic sulfuric steam rising from the lake surface, strong thermal winds causing sudden cold shock, or simple exhaustion during migration. None has been conclusively proven.

For the indigenous Puruhá communities of the surrounding highlands, the event carries deep spiritual significance. The birds are believed to sacrifice themselves to honour the spirits of the lake and to signal the arrival of the rainy season — a moment of agricultural and cosmological importance. The annual gathering of birds is celebrated as a sacred ritual, and the lakes are considered a site of spiritual power. This intersection of ornithology and indigenous cosmology makes the Ozogoche phenomenon one of the most culturally layered events in the natural history of any migratory bird.

In North America, the Upland Sandpiper has a long cultural history. Its wolf-whistle call features in the poetry of Aldo Leopold, who described hearing it as one of the defining sounds of the American prairie. The species was known as the "Upland Plover" until 1973 — a name that reflected its grassland habits and curlew-like appearance — and under that name it became a symbol of the market hunting era, shot in enormous numbers in the late 19th century before legal protection arrived with the Migratory Bird Treaty Act of 1918.