センダイムシクイ 対 ヤナギムシクイ

The most reliable field mark to separate Eastern Crowned Warbler from Greenish Warbler is the bold head pattern of the former: Eastern Crowned Warbler shows a strong, dark lateral crown stripe with a pale, often yellowish median crown stripe, and a prominent supercilium, while Greenish Warbler lacks this crown pattern and instead has a more uniform head with a yellowish supercilium. Both species can show a single pale wingbar, but Eastern Crowned Warbler is more robust and bright, with a slightly forked tail, compared to the slimmer and duller Greenish Warbler. Structure and bill shape also help: Eastern Crowned Warbler has a stronger, paler bill and darker legs, while Greenish Warbler has a finer, darker-tipped bill. Juvenile and immature wing patterns are not described in detail for either species, so focus on head pattern and structure for all ages.

1. Head pattern is key: Eastern Crowned Warbler shows a strong dark lateral crown stripe and a pale, often yellowish median crown stripe, creating a bold head pattern; Greenish Warbler lacks this, showing a more uniform crown with only a yellowish supercilium. This works for all ages and is the most reliable mark.
2. Supercilium: Both species have a pale supercilium, but Eastern Crowned's is longer and more contrasting, while Greenish's is usually yellowish and less striking.
3. Eye-stripe and lores: Eastern Crowned has a dark stripe through the eye and dark lores, adding to the strong facial contrast; Greenish Warbler's face is plainer, with a less distinct eye-stripe.
4. Cheek color: Eastern Crowned has dusky yellow cheeks, which can help in good light; Greenish Warbler's cheeks are not as distinctly colored.
5. Bill structure: Eastern Crowned Warbler has a strong, robust, pale bill; Greenish Warbler has a thinner bill, often with a dark tip to the lower mandible. This is best seen at close range or in photos.
6. Leg color: Eastern Crowned has dark legs; Greenish Warbler's leg color is not highlighted as distinctive, so use with caution.
7. Wingbars: Both can show a single pale wingbar. Some Greenish Warblers (certain subspecies) may show a faint second wingbar, but never as bold as in Two-barred Warbler. Do not rely solely on wingbar count.
8. Upperparts color: Eastern Crowned is dark olive-green above; Greenish Warbler is grayish-green or dull green above, often less bright.
9. Underparts: Eastern Crowned is white below; Greenish Warbler is off-white, sometimes with a yellowish wash on throat and breast in some subspecies.
10. Tail shape: Eastern Crowned has a square, slightly forked tail; Greenish Warbler's tail is more typical and less distinctly shaped.
11. Structure and jizz: Eastern Crowned appears more robust and bright, with a chunkier look; Greenish Warbler is slimmer and more delicate.
12. Size: Eastern Crowned is slightly heavier and bulkier (10.1g), while Greenish Warbler is smaller and lighter.
13. Habitat context: If in boreal or mature temperate forest in East Asia, Eastern Crowned is more likely; in lowland or montane mixed forest, especially in migration, Greenish Warbler is more expected.
14. Voice: If you hear a high, jerky trill with slurred notes, Greenish Warbler is likely; lack of song detail for Eastern Crowned means silence is not diagnostic.
15. Pitfalls: Do not rely on wingbar count alone, as both can show a single wingbar. Always check head pattern and structure for confirmation.

Eastern Crowned Warbler is slightly heavier (body mass about 10.1g [wikidata]) and appears more robust than Greenish Warbler, which is generally smaller and more slender (no direct mass given, but described as smaller and slimmer in build [wikipedia]). In the field, Eastern Crowned Warbler may look chunkier, with a stronger bill and a squarer, slightly forked tail, while Greenish Warbler tends to look more delicate overall.

For all ages, Eastern Crowned Warbler stands out by its dark olive-green upperparts and bright white underparts, but especially by its strong head pattern: a dark lateral crown stripe, a yellowish median crown stripe (though sometimes indistinct), a long yellowish-white supercilium, and a dark eye-stripe with dusky yellow cheeks. It also shows a single pale wingbar and a square, slightly forked tail. Greenish Warbler is grayish-green above and off-white below, with a yellowish supercilium and a single (sometimes faint) wingbar in most populations. Some Greenish Warblers may show traces of a second wingbar, especially in certain subspecies, but never the bold crown pattern of Eastern Crowned. Bill color is also useful: Eastern Crowned has a robust, pale bill, while Greenish Warbler's bill is finer and lacks a pale base. No age-specific upperwing or flight pattern differences are described for either species, so these contrasts apply to all plumages.

Both species are active, insectivorous leaf warblers, often foraging in foliage. Eastern Crowned Warbler may appear a bit more robust and deliberate in movement due to its structure, while Greenish Warbler is typically more restless and agile, flitting through leaves and branches. In flight, Eastern Crowned Warbler's slightly forked tail may be visible, while Greenish Warbler's flight is more typical of small Phylloscopus warblers, quick and direct.

Eastern Crowned Warbler breeds in boreal and temperate forests of the east Palearctic, favoring mature woodland. Greenish Warbler has a broader range, breeding from northeastern Europe across temperate and subtropical Asia, often in lowland deciduous or mixed forests, and moving to montane forests in the non-breeding season, especially in the Himalayas. In vagrancy situations, both can turn up in similar wooded habitats, but Greenish Warbler is more likely as a migrant or vagrant in Western Europe.

Eastern Crowned Warbler's song is not described in the provided notes. Greenish Warbler has a high, jerky trill, sometimes with down- and up-slurred notes, and song structure can vary by population. In the field, song is a useful mark for Greenish Warbler, but lack of detail for Eastern Crowned means this is not a reliable separation based on the current notes.