アカエリヒレアシシギ 対 ソリハシシギ

The most reliable way to separate Red-necked Phalarope from Terek Sandpiper is by bill shape and overall structure: Red-necked Phalarope has a very fine, straight needle-like bill, while Terek Sandpiper shows a distinctly long, upcurved bill with a yellowish base. In flight or at rest, Red-necked Phalarope is compact and small, often showing a white wing stripe (especially in juveniles and adults), whereas Terek Sandpiper is larger, longer-legged, and lacks any strong wing stripe. Juvenile and nonbreeding phalaropes can be confused with small sandpipers, but the combination of structure, bill, and feeding behavior is distinctive. Always check for the black eyepatch on Red-necked Phalarope and the yellow legs and upcurved bill of Terek Sandpiper.

1. Bill shape is the single most reliable mark: Red-necked Phalarope has a fine, straight, needle-like bill; Terek Sandpiper has a long, upcurved bill with a yellowish base (visible at moderate range).
2. Leg color and length: Terek Sandpiper has long, bright yellow legs; Red-necked Phalarope's legs are short and dark, often hidden when swimming.
3. Wing stripe: Red-necked Phalarope of all ages shows a white wing stripe in flight and often at rest; Terek Sandpiper lacks any strong wing stripe.
4. Black eyepatch: Red-necked Phalarope always has a black patch through the eye, even in winter and juvenile plumages; Terek Sandpiper never shows this feature.
5. Supercilium: Terek Sandpiper often shows a white supercilium (eyebrow), sometimes faint, but never as a dark eyepatch.
6. Body shape and size: Red-necked Phalarope is small, compact, and round-bodied; Terek Sandpiper is larger, longer-bodied, and longer-legged.
7. Feeding behavior: Phalaropes often swim in circles on water, a unique behavior; Terek Sandpiper runs actively on mud or sand, never swims in circles.
8. Habitat: Phalaropes are usually on open water or shallow pools, rarely on mud; Terek Sandpiper is almost always on mudflats, estuaries, or river edges.
9. Breeding plumage: Female Red-necked Phalarope is dark grey with a rich chestnut neck and black face; Terek Sandpiper is always grey above and lacks any chestnut or black facial markings.
10. Juvenile confusion: Juvenile phalaropes can look plain, but always have the black eyepatch and white wing stripe; juvenile Terek Sandpipers are structurally different and lack these marks.
11. Vocalization: Phalarope's call is a short 'whit' or 'twit'; Terek Sandpiper gives a longer, high-pitched whistle.
12. Associations: Terek Sandpiper often mixes with turnstones and small plovers; phalaropes are usually in tight flocks or alone on water.
13. Flight jizz: Phalaropes appear fluttery and buoyant in flight, often low over water; Terek Sandpiper is more direct, with longer wings and legs trailing.
14. Bill color: At close range, note the yellowish base to Terek Sandpiper's bill; phalarope's bill is all dark.
15. When in doubt: If the bird is spinning on water, it's a phalarope; if it's running on mud with a long, upcurved bill and yellow legs, it's a Terek Sandpiper.

Red-necked Phalarope is notably smaller and lighter (body mass ~37g [wikidata], length ~18 cm [wikipedia]) than Terek Sandpiper (length 22–25 cm [wikipedia]; no mass data, but visibly bulkier and longer-legged). In the field, Terek Sandpiper will appear closer to a Common Sandpiper in size, with a longer body and legs, while Red-necked Phalarope is petite and dainty, often described as 'miniature' compared to most sandpipers.

Juvenile and nonbreeding Red-necked Phalaropes are grey and brown above with buff underparts and a distinctive black eyepatch, always present even in winter. They show a white wing stripe in flight and at rest, which is a key feature for all ages. Breeding females are dark grey above with a rich chestnut neck and upper breast, black face, and white throat; males are similar but duller. Terek Sandpiper, in all plumages, has a grey back, face, and breast, a white belly, and a white supercilium (variable in prominence). It lacks any strong wing stripe. The legs are yellow and the bill has a yellowish base, both visible at close range. In flight, Terek Sandpiper does not show the bold wing patterns typical of many calidrids or phalaropes. Thus, the white wing stripe and black eyepatch of Red-necked Phalarope are the most consistent plumage clues, especially in young and nonbreeding birds.

Red-necked Phalarope is famous for its habit of swimming in tight circles on water, creating small whirlpools to stir up prey—behavior unique among small waders and never shown by Terek Sandpiper. On land, phalaropes are often seen floating or picking at the water's surface, rarely running. Terek Sandpiper, by contrast, is an active forager, running briskly along mud or sand, chasing mobile prey, and sometimes washing its catch at the water's edge. It is more likely to be seen with other shorebirds, especially turnstones and small plovers, and rarely ventures far onto open water.

Red-necked Phalarope breeds in Arctic wetlands and migrates to winter on tropical oceans, often seen on open water or at coastal upwellings during migration. On passage, it may be found on inland lakes or pools, but is rarely seen on mudflats. Terek Sandpiper breeds along rivers and lakes in the taiga and winters on tropical coasts, favoring muddy estuaries, river mouths, and coastal lagoons. It is much more likely than phalarope to be found on mud or sand, often in mixed flocks with other shorebirds. Thus, context can help: a small wader spinning on open water is almost certainly a phalarope, while a bird running on mud with a long upcurved bill is Terek Sandpiper.

Red-necked Phalarope gives a sharp, quick 'whit' or 'twit' call, often heard during flight or while feeding. Terek Sandpiper's call is a high-pitched whistle, which is longer and more musical than the phalarope's short notes. In practice, calls are not always diagnostic unless heard well, but the phalarope's call is more abrupt and less melodic.