Willet

Willets breed from May through July, with mating occurring in May and early June. They are monogamous, and pairs often remain together for several years — in eastern populations, bonds may persist for life, while in western populations mate fidelity runs at around 65%. Males perform aerial courtship displays, flying with wings held high above the head and fluttering the primary feathers while delivering the ringing 'pill-will-willet' call. The female flies to the male and hovers beneath him as both sing; the pair then slowly descends to the ground together in a coordinated spiral.

The male leads the female through the territory and creates several trial nest scrapes for her to evaluate. The chosen nest is a shallow depression scraped out using feet and breast. It is placed typically on the ground among dense short grass, in cordgrass or saltgrass (eastern birds), or on bare ground or raised sites near water (western birds). The female lines the cup with surrounding vegetation, finer grasses, and sometimes pebbles or shell fragments, producing a finished nest approximately 15 cm across and 5 cm deep.

Clutch size is typically four eggs (rarely three or five), laid over approximately six days. Eggs are olive-buff to greyish with bold, irregular dark brown spots, measuring roughly 4.9–6.2 cm long by 3.4–4.0 cm wide. Incubation lasts 22–29 days, averaging 25 days, and is shared by both parents — with one notable division of labour: only the male incubates at night, and sometimes during midday, while the female takes other shifts.

Chicks are precocial — eyes open, covered in buff or grey down, and able to walk and peck at vegetation within hours of hatching. They leave the nest within one to two days and find their own food from the outset. The female departs the nest site entirely two to three weeks after hatching, leaving the male to complete chick-rearing alone until the young fledge at approximately four weeks of age. Willets raise one brood per year and often nest in loose colonies, particularly along the Atlantic Coast.

Willets are relatively long-lived for shorebirds of their size. The typical lifespan in the wild runs from around five to ten years, and the oldest recorded individual — a banded bird — reached at least ten years and three months. Annual survival rates in adults are estimated at 76–98%, a wide range that reflects variation between years and populations but indicates that most adults that survive their first year have a good chance of reaching breeding age and beyond.

Both males and females can breed as early as their second year, though first-year birds often do not attempt to nest. Mortality causes include predation by hawks, falcons, herring gulls, snakes, otters, crows, ravens, foxes, and raccoons — with eggs and chicks particularly vulnerable to mammalian predators at ground-level nests. Adults are most at risk from aerial predators, particularly during migration when they are moving through unfamiliar areas at night.

Compared to the closely related Wood Sandpiper, which has a recorded maximum of around 11.7 years, the Willet's longevity is broadly similar. The combination of high adult survival, strong mate fidelity, and a precocial chick strategy gives the species a resilient life-history profile. However, the low reproductive rate — one brood per year, four eggs maximum — means sustained habitat loss or elevated adult mortality can quickly tip populations into decline.

The Willet is listed as Least Concern on the IUCN Red List, with a global population estimated at around 250,000 individuals. That headline figure, however, masks a worrying trajectory. Breeding Bird Survey data show an overall decline of approximately 1.9% annually across the eastern region, and the species appeared on the 2014 State of the Birds Watch List as at risk of becoming threatened or endangered without conservation action. It has also been added to the US Fish & Wildlife Service conservation watch list.

The threats are numerous. Coastal development on breeding, stopover, and wintering grounds reduces available habitat, while the invasive reed Phragmites australis replaces the native salt marsh grasses that eastern Willets depend on for nesting. Mosquito ditching, marsh draining, and coastal armoring (sea walls and revetments) reduce both willet abundance and the macroinvertebrate prey communities they rely on. Contaminants accumulating in coastal sediments, avian botulism outbreaks, and collisions with power lines built through wetland breeding sites add further pressure. Western birds face conversion of native grasslands and prairie wetlands to agriculture.

Climate change poses perhaps the most acute long-term threat. A study in Chesapeake Bay projected that Willet populations could decline by nearly 80% with a sea level rise of 3.3–6.6 feet by 2100. This is a stark figure: all of the species' salt marsh nesting habitat sits only inches above current sea level. The eastern subspecies is ranked Highly Vulnerable to climate change along the Atlantic Coast, creating a significant gap between its current Least Concern IUCN category and its real-world vulnerability.

The Willet's story is one of near-extirpation followed by slow, hard-won recovery. By the late 19th century, the eastern population had been devastated by market hunting. Willets were shot in enormous numbers for food and for the millinery trade, and their large size and conspicuous behaviour made them easy targets. John James Audubon had already noted in the 1840s that Willets 'historically' bred near New Bedford, Massachusetts — a sign that the decline was already well advanced by the time systematic records began. A Field & Stream article in 1904 profiled the Willet as a game bird even as the author admitted they had 'rapidly decreased.' By 1910, the species had been virtually extirpated from its entire range north of Virginia.

The Migratory Bird Treaty Act of 1918, which banned the commercial hunting of migratory birds in the United States, was the turning point. With hunting pressure removed, Willets began the slow process of recolonising their former range — but recovery was measured in decades, not years. They reappeared in New Jersey in the 1950s, New York in the 1960s, Maine, Massachusetts, and Connecticut in the 1970s, and New Hampshire and Rhode Island only in the 1980s. The full recolonisation of the historic range took more than 60 years.

Today the eastern population faces a new set of threats that the Migratory Bird Treaty Act cannot address: sea level rise, invasive Phragmites, coastal development, and contaminant accumulation. The species' recovery from hunting is a genuine conservation success story, but it also illustrates how quickly a widespread bird can be pushed to the brink — and how long the road back can be.

Willet courtship is an aerial affair. The male takes to the air above his territory, holding his wings high above his back and fluttering the primary feathers in a slow, exaggerated wingbeat while delivering the ringing 'pill-will-willet' call repeatedly. This display flight is conspicuous and loud, designed to advertise both territory ownership and fitness to prospective mates.

When a female is attracted, she flies to the displaying male and hovers directly beneath him as both birds sing together. The pair then descends slowly to the ground in a coordinated spiral — a behaviour that cements the pair bond and signals readiness to begin nesting. Once on the ground, the male leads the female through the territory, showing her several trial nest scrapes he has prepared in advance. The female evaluates these options and selects the site she prefers, after which she takes the lead in lining the chosen scrape with vegetation.

Males also make a quiet 'click-click' sound during pre-copulatory displays on the ground. Pair bonds, once formed, are strong: eastern birds may remain bonded for life, while western birds show mate fidelity rates of around 65% between seasons. The broken-wing distraction display — used by both sexes when a predator approaches the nest — is equally theatrical. The adult drags a wing along the ground, calling loudly to draw the threat away from eggs or chicks, before suddenly 'recovering' and flying off once the danger has passed.

The question of whether Eastern and Western Willets are one species or two has occupied ornithologists for decades, and the evidence increasingly favours a split. The two forms differ in size, plumage, breeding habitat, vocalisation, and migratory behaviour — and they have very little overlap in their annual ranges, a pattern consistent with separate species rather than subspecies.

In size, the Western Willet (T. s. inornata) is approximately 10% larger overall, with legs and bill around 15% longer than the Eastern bird (T. s. semipalmata). In the field, this gives the Western bird a more attenuated, godwit-like silhouette, while the Eastern bird appears stockier and shorter-billed. In breeding plumage, the Eastern bird is darker and browner with heavier barring on the breast and back; the Western bird is paler and greyer, with finer, less contrasting markings.

The vocal differences, though subtle to human ears, are biologically significant. Eastern birds give a higher-pitched, faster 'pill-will-willet' than Western birds, and playback experiments confirm that individuals respond more strongly to recordings of their own form. Breeding habitats are entirely different — coastal salt marshes for the east, inland prairie wetlands for the west. The two forms also winter on opposite coasts of the Americas: eastern birds head to the Caribbean and South America, while western birds move to the Pacific coast. The American Ornithological Society has not yet formally split the two, but the case is considered strong by many authorities, and a split may be forthcoming.