Shorebirds, with their diverse species and captivating behaviors, offer a fascinating window into the world of avian ecology and migration.
Among these feathered wanderers, the Curlew Sandpiper (Calidris ferruginea) and the Dunlin (Calidris alpina) stand out as distinctive and remarkable.
In this exploration, we delve into the intriguing differences that set these two species apart, ranging from their physical characteristics to their habitat preferences, migratory patterns, and feeding behaviors.
As we navigate the intricacies of their lives, we uncover the unique adaptations that enable these birds to thrive in the challenging environments of their breeding grounds and the seasonal migrations that take them on remarkable journeys across the globe.
Key Differences Between Curlew Sandpiper and Dunlin
The Curlew Sandpiper (Calidris ferruginea) and the Dunlin (Calidris alpina) are both small shorebirds belonging to the sandpiper family, Scolopacidae. While they share some similarities in appearance and habitat.
There are key differences between the two species:
Size
- Curlew Sandpiper: The Curlew Sandpiper is notably larger among the two shorebird species, measuring around 19-23 centimeters (7.5-9 inches) in length.
This size difference is especially evident when comparing them side by side with Dunlins. The larger size contributes to its more striking appearance and distinguishes it from the Dunlin. - Dunlin: Conversely, the Dunlin is smaller, typically measuring about 17-21 centimeters (6.7-8.3 inches) in length. Its relatively compact size is one of the key features that set it apart from the larger Curlew Sandpiper, making it appear more diminutive in comparison.
Bill
- Curlew Sandpiper: The bill of the Curlew Sandpiper is a distinctive feature, setting it apart from the Dunlin. It is longer and slenderer, giving it a more elegant appearance.
This bill shape is well-suited for its feeding behavior, allowing it to probe deeper into mud and sand in search of prey, such as small invertebrates. The slightly curved, elongated bill aids in grasping and extracting food efficiently from the substrate. - Dunlin: In contrast, the Dunlin possesses a shorter and straighter bill. While it is still adapted for probing and foraging, it lacks the length and slimness seen in the Curlew Sandpiper’s bill. This difference in bill shape reflects variations in their feeding strategies and the types of prey they target.
Leg Length
- Curlew Sandpiper: Leg length is another characteristic that distinguishes these two shorebirds. The Curlew Sandpiper boasts longer legs relative to its body size.
These extended legs contribute to its taller stature and enable it to wade through deeper water in search of food. This feature is especially noticeable when the birds are in the field, making them appear more leggy compared to Dunlins. - Dunlin: Dunlins have shorter legs compared to Curlew Sandpipers. Their legs are proportionate to their smaller body size, which makes them better suited for foraging in shallower waters and navigating the intertidal zone. This difference in leg length is an important adaptation to their respective habitats and feeding habits.
Body Shape
- Curlew Sandpiper: The body shape of the Curlew Sandpiper is slimmer and more elegant, lending it a graceful appearance. Its sleek, elongated body, combined with the longer legs and bill, contributes to an overall impression of sophistication.
This body shape is especially noticeable during flight and when observing the birds in their natural habitats. - Dunlin: Conversely, the Dunlin exhibits a slightly stockier or plumper body shape when compared to the Curlew Sandpiper. While not as slender, it is still adapted for agile movement along shorelines and through mudflats. This difference in body shape complements their distinct foraging behaviors and preferences.
Plumage
- Curlew Sandpiper: Both species of shorebirds display variations in plumage depending on age and season, but in breeding plumage, the Curlew Sandpiper stands out with its distinctive reddish-brown head and neck. This coloration is particularly striking and can aid in identification during the breeding season.
- Dunlin: In breeding plumage, Dunlins feature a unique black belly patch, which is one of their hallmark characteristics.
This black patch contrasts with their otherwise light-colored plumage. In non-breeding plumage, Dunlins exhibit a greyish-brown coloration with light streaking.
These plumage variations are important for distinguishing Dunlins from Curlew Sandpipers throughout the year.
Habitat
- Curlew Sandpiper: Curlew Sandpipers primarily inhabit a range of coastal and wetland habitats during their migrations. They can be found in mudflats, estuaries, salt marshes, and shallow coastal lagoons.
These habitats provide them with ample opportunities to forage for their preferred prey, which includes small invertebrates found in the mud and sand. - Dunlin: Dunlins are versatile in their habitat selection, often occupying similar coastal and wetland environments as Curlew Sandpipers.
They frequent mudflats, estuaries, sandy shorelines, and salt pans. While their habitat preferences overlap with Curlew Sandpipers, Dunlins can also be found in freshwater habitats like inland ponds and lakes.
Migration
- Curlew Sandpiper: Curlew Sandpipers undertake extensive migrations, traveling between their breeding grounds in Arctic regions and their non-breeding areas in the Southern Hemisphere. They follow flyways along coasts and can be observed at various stopover sites during migration.
- Dunlin: Dunlins are also migratory birds, but their migration patterns can vary depending on their breeding populations.
Some Dunlins breed in Arctic and subarctic regions and migrate southward for the winter, while others may have shorter migrations within their respective ranges.
Feeding Behavior
- Curlew Sandpiper: Curlew Sandpipers are known for their distinctive feeding behavior, characterized by their long, slender bills that enable them to probe deep into mud and sand to locate small invertebrates. They feed by probing, picking, and using tactile methods to capture prey.
- Dunlin: Dunlins share similar foraging habits with Curlew Sandpipers, including probing the substrate for invertebrates. Their slightly shorter and straighter bills are adapted for similar feeding behaviors, and they are often seen pecking at the surface or probing the mud for food.
Breeding Range
- Curlew Sandpiper: Curlew Sandpipers breed in the high Arctic regions, primarily in Siberia and northern North America. Their breeding grounds are situated in tundra habitats near freshwater bodies, where they nest and raise their young.
- Dunlin: Dunlins also breed in Arctic and subarctic regions, but their breeding range is broader and includes areas in North America, Europe, Asia, and Siberia. They typically nest in shallow depressions on the tundra or near wetlands.
Breeding Plumage
- Curlew Sandpiper: During the breeding season, Curlew Sandpipers display distinctive plumage, with a reddish-brown head and neck. This coloration is especially prominent in males and plays a role in courtship and mate selection.
- Dunlin: In breeding plumage, Dunlins are characterized by a black belly patch, a notable field mark that distinguishes them from Curlew Sandpipers. This patch contrasts with their otherwise pale plumage, making it a key feature for identification.
Non-breeding Plumage
- Curlew Sandpiper: During the non-breeding season, Curlew Sandpipers adopt a distinctive plumage characterized by a greyish-white coloration with subtle streaking on their upperparts. This plumage is particularly effective in providing camouflage in their wintering habitats, which often include coastal mudflats, estuaries, and salt pans.
- Dunlin: In non-breeding plumage, Dunlins typically exhibit a greyish-brown coloration on their upperparts, which is often described as mottled or scalloped.
This plumage helps them blend into the coastal and estuarine environments where they spend the winter months. The combination of streaking and mottling provides effective camouflage, allowing them to forage and rest undisturbed.
Wing Pattern
- Curlew Sandpiper: The wing pattern of Curlew Sandpipers is characterized by a prominent white wing stripe that runs along the length of the wing. This feature is readily visible in flight and during resting periods when the birds are standing or preening.
The contrast between the white wing stripe and the greyish-white plumage is a distinguishing field mark. - Dunlin: Dunlins also exhibit a white wing stripe that runs along the length of their wings, similar to Curlew Sandpipers. This white stripe is a common feature in many sandpipers and is helpful in distinguishing them from other species in flight. The wing pattern of Dunlins is relatively consistent with other Calidris sandpipers, including Curlew Sandpipers.
Leg Color
- Curlew Sandpiper: The legs of Curlew Sandpipers are typically blackish in color. This dark leg color contrasts with their pale plumage and is a useful field mark for identification, particularly when observing them in shallow water or mudflats. The dark legs provide a sharp visual contrast against the substrate they forage on.
- Dunlin: Dunlins often have blackish legs as well, although the intensity of the leg color can vary among individuals. Some Dunlins may have slightly lighter or more mottled leg coloration compared to Curlew Sandpipers, but this distinction can be subtle and may not always be reliable for differentiation.
Voice
- Curlew Sandpiper: Curlew Sandpipers are generally known for being relatively silent birds. They tend to vocalize infrequently, and their vocalizations are not as distinctive or well-documented as some other shorebird species.
When they do vocalize, their calls are typically soft and high-pitched, consisting of short whistles or piping sounds. - Dunlin: In contrast, Dunlins are more vocal and expressive. They produce a variety of calls and songs, especially during the breeding season and while in flocks.
Their vocalizations include a series of sharp, rapid “tu-tu-tu” or “tink-tink-tink” calls. These vocalizations can be helpful for locating and identifying Dunlins in the field.
Bill Length Relative to Body
- Curlew Sandpiper: The bill of the Curlew Sandpiper is notably longer relative to its body size. This characteristic can be observed when comparing the bill length to the overall length of the bird. The longer bill is an adaptation for their feeding behavior, enabling them to probe deeper into mud and sand to capture prey.
- Dunlin: Dunlins have bills that are proportionate to their body size, and while they also use their bills for probing and foraging, their bills are not as long and slender as those of Curlew Sandpipers. The bill length of Dunlins is adapted to their specific feeding habits and prey availability.
Leg Length Relative to Body
- Curlew Sandpiper: The Curlew Sandpiper possesses longer legs relative to its body size, making it appear more leggy compared to the Dunlin.
These extended legs are well-adapted for wading through deeper water and traversing mudflats, allowing them to access a broader range of feeding habitats, especially during migration. - Dunlin: Dunlins have legs that are proportionate to their smaller body size. While their legs are still adapted for efficient movement along shorelines and through mudflats, they appear less leggy compared to Curlew Sandpipers. This difference in leg length complements their distinct foraging behaviors and preferences.
Bill Shape
- Curlew Sandpiper: The bill of the Curlew Sandpiper is long and slender, with a slight curve. This bill shape is specialized for probing deep into mud and sand to capture small invertebrates. The curvature aids in grasping and extracting prey from the substrate, making it an effective tool for their feeding habits.
- Dunlin: Dunlins possess bills that are relatively shorter and straighter compared to Curlew Sandpipers. While they also use their bills for probing and foraging, their bills lack the length and curve seen in Curlew Sandpipers. The bill shape of Dunlins is adapted to their specific feeding strategies.
Migratory Routes
- Curlew Sandpiper: Curlew Sandpipers follow a diverse array of migratory routes depending on their breeding populations. They undertake extensive migrations, traveling between their breeding grounds in Arctic regions (such as Siberia and northern North America) and their non-breeding areas in the Southern Hemisphere.
- Dunlin: Dunlins, like Curlew Sandpipers, are also migratory birds. However, the specific migratory routes taken by Dunlins can vary depending on the breeding populations.
Some Dunlins breed in Arctic and subarctic regions (including North America, Europe, Asia, and Siberia) and migrate southward for the winter, while others may have shorter migrations within their respective ranges.
Conservation Status
- Curlew Sandpiper: As of my last knowledge update in September 2021, the Curlew Sandpiper was classified as “Least Concern” on the International Union for Conservation of Nature (IUCN) Red List.
However, it’s important to note that the conservation status of bird species can change over time due to factors such as habitat loss, climate change, and other threats. - Dunlin: Similarly, as of September 2021, the Dunlin was also classified as “Least Concern” by the IUCN. Like the Curlew Sandpiper, the conservation status of Dunlins can be influenced by habitat degradation and other environmental factors.
Curlew Sandpiper Vs Dunlin: Comparison Table
| Characteristic | Curlew Sandpiper | Dunlin |
|---|---|---|
| Size | Larger | Smaller |
| Bill | Longer and slimmer | Shorter and straighter |
| Leg Length | Longer | Shorter |
| Body Shape | Slimmer and elegant | Slightly stockier |
| Plumage | Variable; reddish-brown in breeding plumage | Variable; black belly patch in breeding plumage |
| Habitat | Mudflats, estuaries, coastal areas | Similar habitats |
| Migration | Migratory | Migratory |
| Feeding Behavior | Similar foraging habits | Similar foraging habits |
| Breeding Range | Arctic regions | Arctic and subarctic regions |
| Breeding Plumage | Distinctive reddish-brown head and neck | Black belly patch |
| Non-breeding Plumage | Greyish-white with light streaking | Greyish-brown with light streaking |
| Wing Pattern | White wing stripe | White wing stripe |
| Leg Color | Blackish | Blackish |
| Voice | Typically silent | Various calls and songs |
| Bill Length Relative to Body | Longer | Shorter |
| Leg Length Relative to Body | Longer | Shorter |
| Bill Shape | Slightly curved | Straight |
| Migratory Routes | Varies depending on populations | Varies depending on populations |
| Conservation Status | Least Concern (IUCN) | Least Concern (IUCN) |
Frequently Asked Questions
Both Curlew Sandpipers and Dunlins typically nest in shallow depressions on the ground in their breeding areas. However, one key difference is their choice of breeding habitats. Curlew Sandpipers tend to nest closer to freshwater bodies in the Arctic tundra, whereas Dunlins may nest in a wider variety of locations, including both wetland and drier tundra habitats.
No, neither Curlew Sandpipers nor Dunlins are known for cooperative breeding. These shorebird species typically have monogamous breeding pairs, with each pair responsible for raising their own young. Cooperative breeding, where other individuals help raise the offspring, is more commonly observed in some other bird species.
The primary threats to these shorebirds in their wintering habitats include habitat loss and degradation due to coastal development, pollution, disturbance by human activities, and climate change. As these birds rely on coastal and wetland areas during migration and in the non-breeding season, changes in these habitats can have adverse effects on their survival.
Both species have adapted to the extreme Arctic conditions by timing their breeding to coincide with the brief Arctic summer when temperatures are relatively warmer. They build nests on the tundra, where the shallow depressions they choose for nesting are often insulated by the surrounding vegetation. Additionally, their breeding plumage provides some insulation, and their eggs are incubated continuously to keep them warm.
While both species engage in courtship displays, one noteworthy difference is in their vocalizations. Dunlins, especially males, are more vocal during courtship and may perform aerial displays while calling. Curlew Sandpipers, on the other hand, are relatively silent during courtship. Instead, they rely more on visual displays, such as postures and movements, as well as their striking breeding plumage to attract mates.
To Recap
The Curlew Sandpiper and Dunlin, though sharing common shorebird traits, possess distinct characteristics that define their uniqueness. From size and plumage to bill shape and migratory routes, each species has evolved to excel in its specific ecological niche.
These birds showcase the remarkable adaptability of avian life, from the Arctic tundra to coastal mudflats. Moreover, their conservation status highlights the importance of safeguarding these delicate ecosystems against growing threats.
As we continue to observe, study, and appreciate these marvelous shorebirds, we gain a deeper appreciation for the intricacies of nature and the need for collective efforts to ensure their survival and the preservation of their habitats.