Marbled Godwit

Marbled Godwits arrive on their breeding grounds in April or May and breed once per year between May and August. They form monogamous pairs for the season; while pairs do not remain together over winter, males and females frequently return to the same territory year after year and often re-pair with the same mate. The male makes several shallow scrapes in the ground with his feet, and the female selects which one to use. Both birds then line the chosen scrape with dry grasses, lichen, moss, or leaves — occasionally with a slight canopy of grass arched overhead. Nests are placed in shortgrass prairie, often in surprisingly open situations with little overhead cover, and may be far from water.

Clutch size is almost always 4 eggs (rarely 3 or 5). Eggs are pale buff or olive-green with small dark brown or purplish-grey spots and scrawls, measuring 5.2–6.6 cm long by 3.6–4.2 cm wide. Both parents share incubation duties over a period of 21–26 days. Incubating birds may sit motionless even when approached closely, relying on their cryptic plumage to avoid detection.

Chicks are precocial — covered in down, eyes open, and able to walk and attempt to feed within hours of hatching. Young leave the nest within 1–2 days. Both parents tend and protect the young for the first 15–26 days, after which the female typically departs, leaving the male to care for the chicks until they fledge at approximately 26–30 days after hatching. Nest success is highest in areas with large amounts of grassland, low levels of cropland-grassland edge, and high wetland density. Predators near developed areas include raccoons and skunks; parents will mob both actively.

The typical lifespan of a wild Marbled Godwit falls between 5 and 15 years, with most birds that survive their first year likely living somewhere in the middle of that range. The oldest confirmed individual on record reached at least 29–30 years — banded as an adult at Humboldt Bay, California, in July 1969 and identified again at Huntington Beach, California, in May 1998. This is an exceptional lifespan for a shorebird of this size, and suggests that individuals that avoid the main mortality risks can survive for decades.

The principal causes of mortality include predation (particularly of eggs and chicks by raccoons, skunks, and raptors), collision with vehicles and power lines, and habitat-related starvation during migration or on degraded wintering grounds. Early mowing of grasslands can kill incubating adults directly. First-year birds face the highest mortality rates, as with most long-lived shorebirds; those that survive to adulthood benefit from strong site fidelity and accumulated knowledge of reliable stopover and wintering sites.

Compared to related species, the Marbled Godwit's potential longevity is broadly similar to other large godwits. The Bar-tailed Godwit has a confirmed maximum of around 32 years, while the Black-tailed Godwit reaches at least 23 years in the wild. The combination of low annual reproductive output (typically one clutch of four eggs per year) and high potential longevity is characteristic of the Scolopacidae family as a whole.

The Marbled Godwit was uplisted from Least Concern to Vulnerable on the IUCN Red List in 2024 — a significant change that most field guides and competitor websites have yet to reflect. The uplisting followed an estimated 20–49% reduction in population over the past three generations (approximately 1994–2021), driven by accelerating declines documented in shorebird migration monitoring data (Smith et al. 2023). The global population is estimated at approximately 270,000 mature individuals, with the beringiae subspecies numbering only around 2,000–3,000.

The primary threat on breeding grounds is conversion of native prairie grassland to cropland. With roughly 70% of the global population breeding in the Prairie Pothole Region, continued grassland loss to agriculture is the single greatest driver of decline. The species has already been extirpated as a breeder from Wisconsin, Iowa, Nebraska, and much of Minnesota — states where it was historically abundant. Tidal mudflat habitat on wintering grounds has also been significantly reduced; in San Francisco Bay alone, intertidal area shrank from around 20,000 acres to roughly 12,000 acres between 1800 and 2000.

Historical market hunting caused severe population crashes in the late 19th and early 20th centuries. Populations partially recovered after the Migratory Bird Treaty Act (1918) ended commercial hunting, but the species never regained its former range. Additional threats include insecticides reducing prey availability on breeding grounds, early mowing destroying nests, oil and gas development in North Dakota, and climate change altering migration timing and reducing intertidal foraging habitat through sea level rise.

The species is listed as a Bird of Conservation Concern by the US Fish & Wildlife Service, appears on the Partners in Flight Yellow Watch List (Continental Concern Score 14/20), and is designated a Species of Greatest Conservation Need in multiple states. Key conservation actions include protecting grassland-wetland complexes, rotational grazing management, and maintaining spill response capacity at key coastal wintering sites.

Two subspecies of Marbled Godwit are currently recognised. The nominate subspecies, Limosa fedoa fedoa, breeds across the northern Great Plains from Montana and the Dakotas north through Alberta, Saskatchewan, and Manitoba, with a small isolated population at James Bay in Ontario and Quebec. This is by far the larger population, accounting for the vast majority of the estimated 270,000 mature individuals worldwide.

The second subspecies, Limosa fedoa beringiae, was only formally described in 1989. It breeds in a restricted area of the Alaska Peninsula, primarily around Ugashik Bay, and numbers approximately 2,000–3,000 individuals. Morphologically, beringiae birds are measurably smaller than nominate birds — with shorter legs and a shorter bill — differences attributed to long-term geographic isolation dating back to the Pleistocene, when the Beringia region was separated from the main continental landmass. The two subspecies also differ in breeding habitat: while fedoa nests in shortgrass prairie, beringiae breeds in wet tundra, lowland meadows, bogs, and coastal marshes.

Migration routes also differ between subspecies. Satellite telemetry has shown that beringiae birds winter along the Pacific Coast from Willapa Bay, Washington, south to Elkhorn Slough, California, and stage at Controller Bay, Alaska, during spring migration before returning to Ugashik Bay. Nominate birds follow more varied routes depending on breeding location, with some populations staging at Great Salt Lake, Utah, and others wintering along the Gulf of California or the US Gulf Coast.

The Marbled Godwit's most likely confusion species is the Long-billed Curlew (Numenius americanus), which shares similar size, warm cinnamon-brown colouring, and habitat preferences across much of the western United States. The key distinction is bill shape: the godwit's bill is slightly upturned, while the curlew's bill curves strongly downward — a difference visible at considerable range. The Long-billed Curlew also shows a more uniform cinnamon underwing without the godwit's rich barring on the upperparts.

Among the four godwit species, the Bar-tailed Godwit (Limosa lapponica) is the most similar in overall shape but is noticeably smaller, has shorter legs (the feet barely extend beyond the tail in flight), and lacks the bright cinnamon underwing lining. In non-breeding plumage, Bar-tailed Godwits are considerably paler and greyer. The Hudsonian Godwit (Limosa haemastica) is darker in breeding plumage with chestnut-red underparts, and in flight shows a distinctive white rump and dark (blackish) wing linings — the opposite of the Marbled Godwit's cinnamon underwing. The Black-tailed Godwit (Limosa limosa) is a vagrant to North America and is readily separated by its bold white wingbar, white rump, and black tail band.

In non-breeding plumage, the Marbled Godwit's retention of warm buff-brown tones year-round is the most reliable distinction from all other godwits, which become noticeably paler and greyer outside the breeding season.

Courtship on the breeding grounds is conspicuous and energetic. Males perform elaborate aerial displays to attract females and advertise territory, flying up to 90 m above the ground in slow, circling flights while calling loudly and continuously. These display flights — sometimes described as figure-eight patterns — can last for several minutes and are often the first indication that Marbled Godwits are present in an area. Males also actively chase rival males from their territories.

On the ground, paired birds engage in ritualised nest-scrape making displays: the male creates several shallow scrapes in the ground with his feet, and the female inspects each one before selecting her preferred site. This scrape-selection behaviour appears to be an important pair-bonding ritual, with both birds spending time at each potential nest site before a final choice is made. Once paired, birds line the chosen scrape together with dry grasses, lichen, moss, or leaves.

Pairs are monogamous within the breeding season. Although they do not remain together over winter, strong site fidelity means that the same male and female often return to the same territory in successive years and frequently re-pair. This long-term pair fidelity — maintained not through year-round association but through independent return to a shared location — is a recurring pattern in migratory shorebirds and suggests that familiarity with a territory and its resources confers a real reproductive advantage.