チュウシャクシギ 対 ダイシャクシギ

The most reliable way to separate Whimbrel from Eurasian Curlew is by size and bill shape: Whimbrel is distinctly smaller with a shorter, kinked bill, while Eurasian Curlew is much larger with a very long, smoothly curved bill. In flight, Whimbrel (in Europe/Asia) shows a striking white rump and lower back, a feature Curlew lacks. Both are brownish waders with long legs and downcurved bills, but careful attention to structure and rump pattern will resolve most confusion, especially with birds in flight or at a distance. Plumage differences are subtle, so structure and flight pattern are your best tools.

1. White rump in flight (Whimbrel only): In Europe and Asia, Whimbrel shows a bright white rump and lower back, easily seen as a flash when the bird takes off or flies away. Eurasian Curlew has a brown rump matching the rest of the upperparts. This is the single most reliable field mark in flight for all ages.
2. Size and bulk: Curlew is much larger and heavier, with a longer neck and legs. If you see both together, the difference is obvious. Alone, compare to nearby waders: Curlew towers over godwits and Redshanks, while Whimbrel is closer in size to Bar-tailed Godwit.
3. Bill shape: Whimbrel's bill is long but noticeably shorter than Curlew's, with a distinct 'kink' near the tip (not a smooth curve). Curlew's bill is extremely long (especially in females), smoothly decurved, and lacks a kink. Bill length is best judged when the bird is side-on and the head is not tilted.
4. Head pattern: Whimbrel shows a strong pale supercilium (eyebrow) that splits the dark crown stripes, giving a striped head appearance. Curlew has a plainer head with a less obvious supercilium and lacks the strong crown stripes.
5. Leg length: Curlew's legs are longer and appear more bluish-grey, while Whimbrel's are shorter and more neutral grey. This is subtle but can help when birds are wading in shallow water.
6. Flight shape: Curlew in flight looks long-winged and long-legged, with feet extending well beyond the tail. Whimbrel is more compact, with shorter wings and legs.
7. Voice: Listen for Curlew's loud, melancholy 'curloo-oo' versus Whimbrel's bubbling, rippling whistle. Calls are often given in flight or when alarmed.
8. Habitat context: In northern breeding areas (tundra, moorland), Whimbrel is more likely. In lowland meadows and grasslands, especially in temperate zones, Curlew is typical. On migration and in winter, both can occur together in estuaries.
9. Seasonal occurrence: Whimbrel is more likely as a passage migrant in many areas, especially in spring and autumn. Curlew may be present year-round or as a winter visitor.
10. Plumage pitfalls: Both are brownish with pale bellies and streaked upperparts. Do not rely on overall color or streaking to separate them; focus on structure and rump pattern.
11. Sex differences: Female Curlew has the longest bill, but sexing Curlew is unreliable unless you see a clear pair. Whimbrel shows little sexual dimorphism in the field.
12. Juvenile confusion: Juvenile and first-winter birds of both species resemble adults in structure and flight pattern, so the same marks apply. The white rump of Whimbrel is present from fledging.
13. Perched vs. in flight: Rump pattern is only visible in flight or when the bird fans its tail. When perched, rely on size, bill, and head pattern.
14. Mixed flocks: In mixed flocks on estuaries, scan for the smaller, more compact birds with strong head stripes (Whimbrel) among the larger, longer-billed Curlews.
15. Geographic context: In North America, beware of Hudsonian Whimbrel, which lacks the white rump; in Europe/Asia, all Whimbrels show the white rump, making separation from Curlew straightforward.

Eurasian Curlew is the largest wader in its range, measuring 50–60 cm in length and weighing on average over 800 g (range 410–1360 g) [wikidata], with a wingspan of 89–106 cm. Whimbrel is much smaller at 37–47 cm in length, 270–493 g in weight, and a wingspan of 75–90 cm [wikipedia]. Even at a distance, Curlew appears bulkier and longer-necked, with a proportionally longer bill and longer legs. When seen together, Whimbrel looks noticeably more compact and lighter.

• Juvenile/immature flight views: Whimbrel (Eurasian/Palearctic) shows a prominent white rump and lower back in flight, contrasting with the rest of the upperparts. Eurasian Curlew has a uniformly brown rump and back, lacking this white patch. This rump contrast is the single most useful mark on birds in flight of any age.
• Adults (perched): Both are generally greyish-brown above and pale below, with streaked upperparts. Whimbrel may appear a bit more crisply patterned, but this is subtle and unreliable at distance. Both have a pale supercilium, but Whimbrel's is typically more pronounced and splits the dark crown stripes, while Curlew's is less obvious.
• Bill: Whimbrel's bill is long and downcurved, but shorter and with a distinct 'kink' near the tip; Curlew's bill is very long, smoothly decurved, and in females especially, can look exaggeratedly long.
• Legs: Both have greyish legs, but Curlew's are often described as greyish-blue and appear longer in proportion to the body.

Both species feed by probing in soft mud or picking prey from the surface, often in similar wetland or coastal habitats. Curlew, being larger, may appear slower and more deliberate in its movements, with a longer reach due to its bill and legs. Whimbrel is more active and can seem more compact and agile. In flight, Curlew's longer wings and legs give it a more languid, powerful flight, while Whimbrel appears quicker and more buoyant.

Both species overlap extensively in coastal mudflats, estuaries, and wet grasslands, especially outside the breeding season. Whimbrel breeds further north (subarctic tundra, moorland) and is more likely to be seen as a passage migrant in many areas, while Curlew breeds across temperate Europe and Asia in open meadows and grasslands. In winter, both can be found together in estuaries, but Curlew is more likely to be resident or wintering in southern parts of its range.

Whimbrel gives a rippling whistle, often a repeated, bubbling trill. Curlew's call is a loud, drawn-out 'curloo-oo', much more ringing and mournful. Both calls are distinctive with experience, but Curlew's is lower-pitched and more resonant, while Whimbrel's is faster and more musical.