Greater Yellowlegs

Greater Yellowlegs arrive on their boreal breeding grounds from late April to May, with pairs forming shortly after arrival. The nest is a simple shallow depression in moss or peat, typically placed at the base of a short coniferous tree, under a low shrub, or beside a moss hummock. It is sparsely lined with grass, leaves, lichen, and twigs, measuring approximately 15 cm across with an inner cup around 2.5 cm deep.

The clutch consists of 3–4 eggs, almost always 4, which are buff to grey-brown in colour and blotched with grey and dark brown markings. Eggs average 49 mm in length and 33 mm in breadth, weighing approximately 28 g each. Both parents are believed to share incubation duties over approximately 23 days. The young are precocial and downy at hatching; they leave the nest within a few hours and begin self-feeding almost immediately.

Both parents tend the chicks and react aggressively to predators, using distraction displays to draw intruders away from the brood. The young are capable of fluttering flight at approximately 25 days and strong, sustained flight by 35–40 days. Only one brood is raised per season. Breeding concludes by late July, and adults — particularly females — begin moving south remarkably early, with some departing the breeding grounds as early as late June.

Precise lifespan data for the Greater Yellowlegs are poorly documented, largely because its remote breeding habitat and dispersed wintering range make long-term individual monitoring difficult. No specific maximum longevity record has been identified in the published literature. The BTO notes that survival data for this vagrant species are not routinely collected in the UK. Based on comparable Tringa sandpipers of similar size — such as the Common Greenshank, which has been recorded living beyond 10 years — it is reasonable to expect that Greater Yellowlegs can live for at least a decade under favourable conditions.

Mortality causes include predation at all stages of the life cycle, with nest predation a significant factor on the breeding grounds. Adults use distraction displays to protect chicks, but ground nests remain vulnerable to foxes, corvids, and mustelids. During migration, birds face exhaustion, adverse weather, and collision risks. Hunting in parts of the Caribbean and South America represents an ongoing and poorly quantified source of adult mortality. Some individuals — particularly immatures — appear to carry significant parasite loads that prevent them from completing northward migration, leading to oversummering on the wintering grounds in coastal South America.

The Greater Yellowlegs is listed as Near Threatened on the IUCN Red List — a status it was uplisted to in 2016 from Least Concern. The global population is estimated at approximately 140,000 individuals (Partners in Flight; Audubon), making it one of the rarer shorebirds in North America despite its apparent abundance during migration. The 2025 State of the Birds report designated it an Orange Alert Tipping Point species, meaning it has lost more than 50% of its global population over the past 50 years and has shown accelerated declines within the past decade. Partners in Flight rates it 14 out of 20 on the Continental Concern Score.

Wetland habitat loss and degradation on the wintering grounds is the primary current threat. The species uses dispersed wetland habitats rather than concentrating at a few key sites, which provides some resilience but makes population monitoring difficult.

Climate change threatens both boreal breeding habitat and wetland availability on wintering grounds. The attrition of small, temporary wetlands used as migration stopover sites — driven by intensive agriculture — is an additional pressure.

Hunting played a major historical role in population decline. Before the Migratory Bird Treaty Act of 1918, Greater Yellowlegs were heavily shot as game birds; some hunters took hundreds in a single season, and the species' habit of circling back after being flushed made it an easy target. Populations recovered following legal protection in North America. Today, hunting in mainland North America is prohibited. In parts of the Caribbean and South America, however, thousands of migrating shorebirds — including Greater Yellowlegs — are still shot annually, largely without regulation, representing an ongoing and poorly quantified mortality source.

Separating the yellowlegs from each other is one of the classic shorebird identification challenges — and the two species frequently occur together during migration, removing the luxury of memory comparison. Size is the most obvious difference between the Lesser Yellowlegs (Tringa flavipes) and the Greater: the Greater is roughly 50% larger. But this is only useful when both species are present for direct comparison. Bill length is the most reliable single-bird distinction: the Greater's bill is approximately 1.5 times the length of its head and has a slight upward curve, while the Lesser's bill barely exceeds head length and is straight and needle-fine. The Greater's bill is also noticeably thicker at the base. The call clinches identification at any distance: three loud, emphatic notes from the Greater versus two softer notes from the Lesser.

The Common Greenshank (Tringa nebularia) is the Greater Yellowlegs' closest relative and shares several features: a long, slightly upturned bill, a bold white rump in flight, and a coarse dark breast pattern in breeding plumage. The Greenshank's legs are greenish-grey rather than yellow, and its call — a ringing "tew-tew-tew" — is similar enough to cause confusion. In Europe, the Greenshank is the default large Tringa wader; any bird with bright yellow legs should trigger immediate scrutiny.

The Willet is larger and stockier, with a thick straight bill and grey legs, and shows a bold black-and-white wing pattern in flight that immediately separates it. The Spotted Redshank (Tringa erythropus) has red legs and a drooped bill tip, and lacks the yellow leg colour entirely.

The Greater Yellowlegs performs one of the more elaborate courtship displays of any North American shorebird, though it takes place in such remote habitat that it is rarely observed. Males begin displaying shortly after arriving on the breeding grounds in late April or May. The aerial display is the centrepiece: the male rises steeply into the air above the bog, then alternately rises and falls with a series of flutters and long glides. All the while he delivers a loud, ringing, repeated song — audible from a considerable distance across the open muskeg. The display flight can last several minutes.

On the ground, the courting male runs in circles around the female, pausing to pose with wings raised above the body — a posture that displays the white underwing and rump. Mating follows if the female is receptive.

Pairs are presumed to be monogamous for the season, though the remote nature of the breeding habitat means long-term pair fidelity has not been confirmed. Both sexes are believed to share incubation duties, and both attend the chicks after hatching, reacting aggressively to any intruder that approaches the nest or brood.

The species' habit of perching atop spruce trees — unusual for a ground-nesting shorebird — is most pronounced during the breeding season, when adults use elevated vantage points to scan for approaching predators. This tree-perching behaviour, combined with the elaborate aerial song flight, gives the Greater Yellowlegs a distinctly un-wader-like quality on its breeding grounds.