キマユヒヨドリ 対 Javan Bulbul

The most reliable field mark to separate Yellow-browed Bulbul from Javan Bulbul is the presence of a prominent yellow brow and all-yellow underparts in the Yellow-browed Bulbul, contrasting with the Javan Bulbul’s more uniformly olive or greenish plumage and lack of a strong yellow eyebrow. Both species are forest bulbuls, but their ranges do not overlap: Yellow-browed is found in southern India and Sri Lanka, while Javan Bulbul is restricted to Java. Structure is similar, but the Yellow-browed lacks a crest and shows a brighter, cleaner yellow below, while Javan Bulbul is generally more muted and greenish. Age-related wing patterns are not described for either species, so focus on head and underpart color for all ages.

1. Yellow brow and facial pattern: Yellow-browed Bulbul always shows a prominent yellow brow and a yellow 'goggle' around the eye. Javan Bulbul lacks this feature and has a more uniform face. This is the single most reliable mark at all ages and in all conditions.
2. Underparts color: Yellow-browed Bulbul is bright yellow below, sometimes tinged green or bronzy depending on subspecies, but always distinctly yellow. Javan Bulbul is olive or greenish below, never clean yellow.
3. Upperparts: Both are olive-green above, but Yellow-browed Bulbul may appear brighter or more contrasting due to the yellow underparts and brow. Javan Bulbul is more uniformly greenish or olive, sometimes with subtle streaking.
4. Crest: Yellow-browed Bulbul lacks a crest, giving it a smooth, rounded head profile. Javan Bulbul’s crest is not described, but if present, could be a subtle difference (not diagnostic from these notes).
5. Bill and iris: Yellow-browed Bulbul has a black bill and reddish-brown iris; these features are not described for Javan Bulbul, so use with caution.
6. Sex and age: Both species show little or no sexual dimorphism; males and females look alike. No juvenile or immature-specific wing or flight marks are described for either, so do not rely on age-related differences.
7. Flight views: No distinctive wing or tail patterns are described for either species in flight; focus on body and head color even in brief or distant views.
8. Subspecies variation: Yellow-browed Bulbul subspecies vary in brightness and greenish tinge, but all retain the yellow brow and yellowish underparts. Javan Bulbul may show some rufous or streaked tones, but never the bright yellow.
9. Range and location: If you are in Java, only Javan Bulbul is possible; if in southern India or Sri Lanka, only Yellow-browed. There is no overlap.
10. Habitat: Both prefer forest, but only Yellow-browed is found in the Western Ghats, Nilgiris, and Sri Lanka; Javan Bulbul is restricted to Java’s montane forests.
11. Alternate names confusion: Javan Bulbul is sometimes called 'streaked bulbul' or 'green mountain bulbul', but do not confuse with other streaked or olive bulbuls. Always check for yellow brow and underparts.
12. Pitfalls: In poor light, Javan Bulbul may appear yellower than it is, but will never show the crisp yellow brow and clean yellow below of Yellow-browed. Watch for subtle facial contrast.
13. Perched vs. moving: Both species perch openly at times; the yellow brow of Yellow-browed is often visible even when partially obscured by foliage.
14. Community tip: When in doubt, focus on the face: the yellow brow is unique to Yellow-browed among these two.
15. Not diagnostic: Size, behavior, and voice are not described as useful separators in these sources.

Both species are medium-sized bulbuls, with the Yellow-browed Bulbul about 20 cm (7.9 in) in length [wikipedia]. No direct size information is given for Javan Bulbul, but as both are typical bulbuls, expect them to be similar in overall proportions and mass. Size is not a reliable separator in the field between these two.

No age-specific wing or flight pattern differences are documented for either species; both should be judged primarily on overall coloration and head pattern at all ages.

• Yellow-browed Bulbul: Always shows a distinct yellow brow and 'goggle' (eyering area), with olive-green upperparts and bright yellow underparts. Subspecies vary slightly: northern Western Ghats birds are paler and duller, southern birds are brighter yellow, and southwestern Sri Lankan birds are greener below. Sexes are alike, and there is no crest.

• Javan Bulbul: Lacks a strong yellow brow; instead, it is more uniformly olive or greenish above and below, sometimes with subtle streaking or rufous tones (as suggested by alternate names), but never the clean, bright yellow underparts of Yellow-browed. No mention of a goggle or strong facial contrast.

In all plumages, the Yellow-browed’s yellow brow and underparts are the key contrast.

No behavioral differences are described in the sources. Both are typical forest bulbuls and likely show similar feeding and perching behavior. Behavior is not diagnostic.

Habitat is a strong separator by geography: Yellow-browed Bulbul is found in forests of southern India and Sri Lanka, while Javan Bulbul is endemic to montane forests of Java, Indonesia [wikipedia]. If you are outside Java, you are not seeing Javan Bulbul; if you are outside southern India/Sri Lanka, you are not seeing Yellow-browed. Both prefer forested habitats, so habitat type alone is not diagnostic within their ranges.