Lesser Yellowlegs

Pairs form shortly after birds arrive on the breeding grounds from late April, with most arriving by mid-May. The Lesser Yellowlegs is seasonally monogamous; pairs typically do not re-mate in subsequent years. Courtship involves males performing undulating display flights over communal foraging areas and nesting territories, often alongside rival males. At the peak of the display, the male glides with tail spread and neck craned upwards — a posture that can be seen from some distance across open boreal terrain.

Before committing to a final nest site, a pair may excavate and line up to 75 separate scrapes in the ground — a level of prospecting behaviour apparently unique among shorebirds. The final nest is a shallow depression about 10 cm across and 3.5 cm deep, typically placed next to a fallen log, branch, or low shrub, and sparsely lined with dry grass, leaves, moss, or twigs gathered nearby. Nest sites are generally drier and more densely vegetated than those of the Greater Yellowlegs, and almost always within 200 metres of water.

The clutch normally consists of four eggs (range 3–5), buff, grey-brown, or greenish in ground colour and spotted in various shades of brown. Eggs average 3.9–4.7 cm in length and 2.7–3.1 cm in width. Both parents incubate for 22–23 days, and eggs hatch within a few days of each other.

The young are precocial: downy chicks leave the nest within hours of hatching and feed themselves immediately. Both parents initially brood and guide the chicks, flying ahead to suitable foraging areas and calling the young forward. The female typically departs around 11 days after hatching, leaving the male to care for the chicks until they fledge at 22–31 days. There is one brood per season, though pairs will re-nest after a failure. Most birds first breed at age two, though some attempt breeding in their first year.

Precise longevity data for the Lesser Yellowlegs are limited by the challenges of tracking small migratory shorebirds across a range spanning Alaska to Argentina. Most individuals are believed to survive 3–5 years in the wild, based on survival rate estimates from banding studies, though the true upper limit of lifespan is likely higher than current records suggest.

Annual survival rates are influenced heavily by conditions encountered along the entire migratory route — not just on the breeding grounds. Hunting pressure in the Caribbean and South America, habitat quality at key stopover sites, and the energetic demands of transoceanic flights all affect survival. Juveniles making their first southward migration face the greatest risks, navigating thousands of kilometres without the benefit of prior experience.

Most birds first breed at age two, though some attempt breeding in their first year. The female's early departure from the brood — typically around 11 days after hatching — means she can begin pre-migratory fattening sooner than the male, potentially improving her survival prospects on the southward journey. The male, remaining with the chicks until fledging at 22–31 days, departs later and arrives on wintering grounds in a more depleted condition.

The Lesser Yellowlegs was uplisted from Least Concern to Vulnerable on the IUCN Red List in 2024, as part of a broader reassessment of migratory shorebirds that revealed widespread, accelerating declines across the group. The global population is estimated at 527,000–660,000 mature individuals. The North American Breeding Bird Survey records an average annual decline of -2.36% from 1970 to 2019 — a cumulative loss of approximately 63–70% depending on the survey method. Between 2003 and 2015, surveys in Alaska recorded declines of up to 9% per year. COSEWIC listed the species as Threatened in Canada in 2020, estimating a 25% decline over three generations (12 years) based on BBS data, and greater than 50% over 10 years based on International Shorebird Surveys.

The greatest current threat is hunting. The Lesser Yellowlegs is likely the most widely hunted shorebird in the Atlantic Americas Flyway. Legal hunting continues in parts of the Caribbean — particularly Barbados, Guadeloupe, and Martinique — and in South America, where current harvest levels are considered unsustainable. Hunting in mainland North America was banned by the Migratory Bird Treaty Act in 1918, which allowed populations to partially recover from catastrophic 19th-century market hunting. That recovery is now being reversed.

Habitat loss compounds the pressure: ongoing loss of wetland and intertidal habitat in South America from agricultural expansion and shoreline development, and degradation of key stopover sites such as Quill Lakes in Saskatchewan, reduce the species' ability to refuel during migration. Climate change adds further stress through increased drought risk on breeding grounds, coastal flooding, and greater hurricane severity during fall migration. Agricultural pesticide use in the Prairie Pothole Region may also reduce food availability at critical stopover sites.

Conservation responses include the International Lesser Yellowlegs Working Group, formed under the Road to Recovery initiative, and the Western Hemisphere Shorebird Reserve Network (WHSRN). The species is designated an Orange Alert Tipping Point species in the 2025 State of the Birds report — meaning it has lost more than 50% of its population in 50 years and declines are accelerating.

The Lesser Yellowlegs has lived through one of the most dramatic conservation arcs of any North American shorebird — a story of near-destruction, partial recovery, and renewed decline that spans more than 150 years.

In the 19th century, the species was shot in enormous numbers by market hunters supplying game to urban restaurants and markets. Its fatal vulnerability was behavioural: rather than fleeing when a flockmate was shot, Lesser Yellowlegs would hover and circle over the fallen bird, allowing hunters to continue shooting until the entire flock was gone. By 1916, ornithologists were reporting that flocks had vanished from sites where they had been abundant in 1870.

The Migratory Bird Treaty Act of 1918 — signed between the United States and Canada — banned the hunting of shorebirds in North America and allowed populations to begin recovering over the following decades. That recovery was slow and uneven, but by the mid-20th century the species had re-established itself at many sites from which it had disappeared. It was a rare conservation success story: a bird pulled back from the brink by a single piece of legislation.

That recovery, however, was never complete. From the 1970s onwards, a new set of pressures — legal hunting in the Caribbean and South America, wetland habitat loss, and climate change — began reversing the gains. The causes this time are more diffuse and harder to address with a single treaty, which is why the species' current trajectory is proving more difficult to halt than the 19th-century crisis it survived.

Courtship begins shortly after birds arrive on the breeding grounds in late April and early May. Males perform undulating display flights over communal foraging areas and nesting territories — a looping, roller-coaster aerial display that can involve several males flying simultaneously over the same area. At the peak of each undulation, the male glides with his tail fanned and neck craned upward, producing a sustained, ringing song that carries across the open boreal landscape.

Between aerial bouts, males perch prominently on top of dead trees or snags and call loudly — a conspicuous advertisement that serves both to attract females and to warn rival males. Males guard females closely from competitors during courtship and the egg-laying period.

The nest-scrape selection process is one of the most elaborate pre-nesting behaviours documented in any shorebird. Before a final nest site is chosen, a pair may excavate and line up to 75 separate scrapes — see Nesting and Breeding for full details. This extended prospecting may allow the pair to evaluate multiple sites for predator activity, proximity to water, vegetation cover, and drainage — factors that collectively determine nest success.

The Lesser Yellowlegs is a regular autumn vagrant to the UK, with around five birds recorded each year — almost all between August and October, consistent with the southward migration of juveniles and adults from North American breeding grounds. The first confirmed British record dates to 1854–55, when a bird was shot at Misson, Nottinghamshire. For most of the 20th century, each new arrival required formal review by the British Birds Rarities Committee (BBRC). By the 2010s, records had become frequent enough that the BBRC removed the species from its national rarities list in January 2019 — a significant milestone that reflects both the species' increasing regularity and, possibly, changes in observer coverage and awareness.

Records span the entire country, but south-west England — Cornwall, Devon, and the Isles of Scilly — produces the highest concentration, particularly during and after westerly Atlantic weather systems that can carry transatlantic migrants off course. Coastal lagoons, estuaries, and freshwater pools with muddy margins are the most productive habitat types to check. Inland records are less frequent but do occur; the species occasionally settles for extended periods, as demonstrated by an individual that wintered at Nosterfield Quarry, North Yorkshire from autumn 2019 through to early 2020.

Elsewhere in Europe, the species is recorded as a vagrant across the Atlantic fringe — Ireland, Iceland, the Azores, and mainland western Europe — with occasional records from further east. Given the species' documented capacity for multi-day transoceanic flights, European vagrancy is best understood not as an accident but as a predictable consequence of the migration strategy used by eastern-breeding birds.