The marbled godwit (Limosa fedoa) and the bar-tailed godwit (Limosa lapponica) are two species of large, long-legged shorebirds belonging to the genus Limosa. Both species breed in northern latitudes and migrate long distances to spend the non-breeding season along coastlines and wetlands further south. While the two godwit species share some characteristics, there are also notable differences between them in terms of physical features, breeding and migration patterns, habitat and behavior. This article provides an overview of how to distinguish between marbled and bar-tailed godwits and highlights the key similarities and differences between the two species.
Quick identification tips
There are a few quick tips that can help identify whether a godwit is a marbled or bar-tailed:
- Plumage – Marbled godwits have boldly patterned black and chestnut breeding plumage. Bar-tailed godwits are more subtly patterned in gray, brown and buff.
- Tail pattern – Marbled godwits lack any barring on the tail at any time of year. Bar-tailed godwits have distinctive black barring on the tail.
- Beak – Marbled godwits have a long, slightly upturned beak. Bar-tailed godwits have a straighter, heavier beak.
- Legs – Marbled godwit legs are completely black. Bar-tailed godwits have legs with a pinkish or flesh-colored hue.
- Size – Marbled godwits are very slightly larger on average than bar-tailed godwits.
If observing a godwit during the breeding season when their plumage is brightest, the plumage differences provide a quick distinction. Outside of breeding plumage, the tail patterns and leg color are the best clues for identification. The beak and size differences are more subtle.
Plumage and Molt
Marbled and bar-tailed godwits have distinct plumages that can help distinguish between the two species.
Marbled Godwit
- Breeding plumage: Boldly patterned in black and rich chestnut on the head, neck and underparts. The chestnut neck and chest is separated from the black belly by a white line. The back and wings are mottled silvery-gray.
- Non-breeding plumage: More subdued gray-brown overall with diffuse chestnut coloring on the neck and underparts. Retains some black and white patterning on the belly.
- Molt pattern: Breeding plumage molt is complete in early fall. Molt continues through the winter into early spring to attain non-breeding plumage.
Bar-tailed Godwit
- Breeding plumage: Subtly patterned overall in buff, chestnut, brown and gray. Bold patterned black and chestnut only on the head. Underparts are buff with some spotting or barring.
- Non-breeding plumage: Plain gray-brown above and pale below with minimal patterning.
- Molt pattern: Breeding plumage molt starts earlier in summer and is complete by fall migration. Molt continues on wintering grounds.
The key plumage difference is the bold black and chestnut breeding colors of the marbled godwit compared to the more subtle and uniform plumage of breeding bar-tailed godwits. Outside of breeding plumage, the species can appear more similar gray-brown overall.
Size and Structure
Marbled and bar-tailed godwits have similar body size and proportions but some subtle structural differences.
Feature | Marbled Godwit | Bar-tailed Godwit |
---|---|---|
Length | 16-19 in (40-48 cm) | 15-17 in (38-43 cm) |
Wingspan | 30-32 in (76-81 cm) | 28-30 in (71-76 cm) |
Weight | 12-21 oz (340-595 g) | 9-15 oz (255-420 g) |
Beak shape | Long, slight upward curve | Shorter, straight |
Beak length | 3.5-5 in (9-13 cm) | 2.75-3.5 in (7-9 cm) |
On average the marbled godwit is very slightly larger with a longer, more upward curving beak. However there is extensive overlap in size and beak shape making them difficult to distinguish by size alone.
Geographic Ranges
Both marbled and bar-tailed godwits have circumpolar breeding ranges and widespread coastal wintering ranges, but there are some key differences.
Marbled Godwit
- Breeding range: Western and central Canada to Alaska.
- Wintering range: Along the Pacific and Atlantic coasts of the Americas from California to Peru and New Jersey to Florida.
- Migration: Long-distance overland migrations between breeding and wintering grounds.
Bar-tailed Godwit
- Breeding range: Northern Scandinavia through Russia.
- Wintering range: Coastal east Asia, Australia, New Zealand, eastern and western Africa.
- Migration: Circumpolar migration pathways often over open ocean.
There is no overlap between the species’ breeding ranges in North America (marbled) and northern Eurasia (bar-tailed). During the non-breeding season they occupy broadly separated coastal regions. Only in migration do they overlap along the Pacific coast of North America.
Breeding Habitat and Nesting
The breeding habitats and nesting behaviors of marbled and bar-tailed godwits are adapted to their different Arctic and subarctic breeding ranges.
Marbled Godwit
- Breeding habitat: Northern grasslands and wetlands – prairie potholes, marshes, wet meadows.
- Nest: Shallow depression lined with vegetation on the ground.
- Eggs: 4 olive to buff-colored eggs.
- Incubation: 22-25 days solely by the female.
- Chicks: Precocial, feed themselves but tended by parents.
Bar-tailed Godwit
- Breeding habitat: Tundra and mossy bogs.
- Nest: Grass-lined depression on the ground.
- Eggs: 4 stone-colored eggs with dark spotting.
- Incubation: 21-22 days by both sexes.
- Chicks: Precocial, feed themselves but brooded by parents.
They differ in typical nesting habitat but share similar ground nesting behavior. Clutch size and chick rearing are comparable for the two species.
Diet and Feeding
The diets of marbled and bar-tailed godwits are fairly similar as they are both tactile foragers taking small prey from wet and flooded soils or soft muds.
Marbled Godwit
- Probes for prey items in mud or wet grassland soils.
- Feeds primarily on insects, crustaceans, mollusks and other small invertebrates.
- Will also consume eggs and larvae of amphibians and some plant material.
- Uses long bill to probe deeply into substrates.
Bar-tailed Godwit
- Probes into estuarine muds to capture polychaete worms and bivalves.
- Also feeds on crustaceans and insects when breeding in tundra habitats.
- Employs shorter bill for efficient shallow probing.
Both species use their long bills to seek prey while wading through shallow wetlands or intertidal zones. Since they feed mostly in soft soils and muds, direct competition is limited between these species even where they co-occur.
Conservation Status
Marbled and bar-tailed godwits have different conservation statuses and population trends reflecting their distinct global ranges.
Species | Conservation Status | Population Trend |
---|---|---|
Marbled Godwit | Near Threatened | Declining |
Bar-tailed Godwit | Least Concern | Stable |
The marbled godwit has a more restricted range centered in North America where breeding habitat loss has driven declines. Widespread bar-tailed godwits remain stable across their broad range and habitats.
Key Identification Tips
In summary, there are several key features that can help identify marbled and bar-tailed godwits and distinguish between them:
Marbled Godwit
- Bolder black and chestnut breeding plumage
- No barring on tail at any time of year
- Long, slightly upturned bill
- Black legs
- Breeds in prairies and wetlands
- Winters along Pacific and Atlantic coasts
Bar-tailed Godwit
- More subtly patterned gray, brown and buff breeding plumage
- Heavily barred black and white tail
- Shorter, straight dark bill
- Pinkish legs
- Breeds on northern tundra
- Winters along coasts of Africa, Asia, Australasia
Outside of breeding plumage, tail pattern and leg color offer the quickest clues. Bill shape, molt timing, geographic ranges, breeding habitat and conservation status also aid identification. With good views and a little practice, the marbled and bar-tailed godwits can be confidently distinguished even in their less colorful non-breeding plumages.
Marbled Godwit vs Bar-tailed Godwit: Further Comparisons
Migration
The marbled and bar-tailed godwits undertake some of the longest known migrations in the animal kingdom, but follow markedly different routes between their breeding and wintering grounds.
Marbled godwits embark on long-distance flights across interior North America between their Canadian nesting sites and Pacific and Atlantic coastal wintering grounds. Round-trip migrations can exceed 9,300 miles (15,000 km).
Bar-tailed godwits make non-stop transoceanic migrations of over 6,200 miles (10,000 km) following coastlines across eastern Asia and the Pacific to Australia and New Zealand, the longest known non-stop flight of any bird.
These marathon migrations are fueled by large fat reserves and adaptations for long-distance flight including large breast muscles and hearts. Bar-tailed godwits shrink and re-grow their internal organs over their migratory cycle.
Both species travel in large flocks during migration, but bar-tailed godwits have a more communal migration culture that sees whole populations converge on a handful of stopover sites.
Lifespan and longevity
Both species of godwit are relatively long-lived shorebirds. Lifespans are estimated to be:
- Marbled godwit: 10 to 12 years
- Bar-tailed godwit: 15 to 20 years
The bar-tailed godwit holds the known longevity record for shorebirds, with one individual surviving over 30 years between initial banding and final sighting.
Their long lifespans allow the godwits to take several years to reach sexual maturity and for adults to accumulate extensive experience migrating between nesting and wintering sites over many seasons.
Mimicry
The marbled godwit shares a unique relationship with the larger long-billed curlew where the two species converge on prairie breeding grounds. Here, marbled godwits have evolved a curlew-like decurved bill and mimics the curlew’s distinctive courting displays during the breeding season.
This anti-predator adaptation allows the marbled godwit to gain protection through mimicry of the larger and more aggressive curlew species and reduces aggression between the competing species sharing breeding habitat.
No mimicry relationship occurs between marbled and bar-tailed godwits since they occupy disconnected breeding ranges.
Symbolism and Culture
The bar-tailed godwit appears prominently in the mythology of indigenous cultures across the Asia-Pacific region including Australia and New Zealand where it winters.
For the Aboriginal people of northern Australia, the godwit is a symbol of travel and safe return. In Maori legend, the godwit’s prodigious migration linked New Zealand to the northern world.
The marbled godwit has limited cultural significance given its more restricted North American range overlapping with fewer indigenous cultures.
However, in poetry and literature the marbled godwit’s ornamental breeding plumage and dramatic migrations have inspired creative comparisons to other colorful transient phenomena like rainbows, sunrises, and roses blooming.
Threats and Conservation
Both godwit species face a range of threats on their breeding grounds, migratory routes, and in wintering regions. However, marbled godwits are more imperiled overall:
Marbled godwit
- Habitat loss in Canadian grassland and wetland breeding areas
- Low population numbers
- Climate change disrupting migration timing and breeding success
- Pollutants impacting migration stopover and wintering habitats
Bar-tailed godwit
- Habitat changes at migratory staging areas like the Yellow Sea
- Human disturbance at wintering wetlands
- Hunting pressure on island stopovers
- Climate change impacts on Arctic breeding ecology
Conservation actions for these species include protecting remaining breeding habitats, advocating reduced harvest/hunting, managing human disturbance, and monitoring populations. As wide-ranging migrants, godwits face challenges requiring international cooperation across range states.
Conclusion
In summary, the marbled and bar-tailed godwits exhibit many similarities as large migratory shorebirds but also have distinct differences in their plumage, geographic ranges, habitat use, conservation status, and cultural roles. Marbled godwits and bar-tailed godwits offer rich opportunities for comparison in how divergent evolutionary paths and adaptations shape closely related species sharing a similar ecological niche. Careful observation and an understanding of key identification cues allow even amateur bird enthusiasts to readily distinguish these two elegant godwit species across their ranges.