シロハラムクドリ 対 チャバネテリムク

The most reliable field mark to separate Violet-backed Starling from Chestnut-winged Starling is the strong sexual dimorphism and plumage contrast in Violet-backed: adult males are strikingly iridescent violet above with pure white underparts, while females are brown and heavily streaked, resembling a thrush. Chestnut-winged Starling, by contrast, lacks this dimorphism and is characterized by uniformly dark plumage with chestnut-colored wings, without the bold white or streaked underparts. If you see a starling with a bright violet back and clean white belly (male) or a heavily streaked brown-and-white bird (female), it is Violet-backed; a darker bird with chestnut wings in the rainforest is Chestnut-winged. Immature and female Violet-backed Starlings are a common pitfall, as their streaked pattern can be mistaken for other species, but Chestnut-winged never shows this thrush-like streaking.

1. Adult male Violet-backed Starling is unmistakable: Look for a small starling with a shimmering violet head and back, and a pure white belly and breast. No other starling in the region shows this combination.
2. Adult female Violet-backed Starling is heavily streaked: Females are brown above with bold streaks and white below with heavy streaking, giving a thrush-like appearance. Chestnut-winged Starling never shows this pattern.
3. Chestnut-winged Starling has chestnut wings: In all plumages, look for the rich chestnut coloration on the wings, especially visible in flight or good light. The rest of the plumage is dark and lacks strong contrast.
4. No white underparts in Chestnut-winged: If you see a starling with clean white underparts (male) or white with heavy streaking (female/immature), it is not Chestnut-winged.
5. Sexual dimorphism is key: Only Violet-backed Starling shows strong differences between male and female; Chestnut-winged is similar in both sexes.
6. Iridescence is diagnostic for Violet-backed males: The violet gloss is unique and not matched by the more matte, dark plumage of Chestnut-winged.
7. Juvenile/immature confusion: Young Violet-backed Starlings resemble adult females and can be mistaken for other streaked birds, but Chestnut-winged juveniles are not streaked.
8. Habitat context: In dense rainforest, Chestnut-winged is more likely; at woodland or forest edge, expect Violet-backed.
9. Feeding height: Violet-backed is often high in the canopy, rarely on the ground, which may help if you see a starling foraging low.
10. Bill, legs, and iris: Both species have dark bills and legs, but Violet-backed has yellow irises in both sexes, which may be visible at close range.
11. Perched vs. flight views: In flight, look for chestnut in the wings (Chestnut-winged) versus violet gloss or streaked brown (Violet-backed). Perched, the white underparts or heavy streaking of Violet-backed are obvious.
12. No strong size difference: Do not rely on size to separate these two.
13. No voice differences described: Vocalizations are not a reliable separator based on current notes.
14. Pitfall: Female and immature Violet-backed Starlings are often misidentified as other streaked birds; always check for the combination of streaked underparts and habitat.
15. Contextual clues: Consider the surrounding habitat and flock composition, as Violet-backed may join mixed flocks in open woodland, while Chestnut-winged is more restricted to rainforest.

Violet-backed Starling is a relatively small starling, measuring about 17–18 cm in length [wikipedia]. Chestnut-winged Starling's precise measurements are not given in the notes, but both are medium-small starlings and likely overlap in size. Size alone is not a reliable separator in the field between these two species.

• Adult males (Violet-backed Starling): Iridescent violet head and back, pure white underparts. This bold contrast is unique among starlings in the region. Chestnut-winged Starling males do not show this coloration; instead, they are dark overall with chestnut-colored wings, lacking any white underparts or violet gloss.
• Adult females (Violet-backed Starling): Brown upperparts with bold streaks and white, heavily streaked underparts, giving a thrush-like look. Chestnut-winged Starling females do not have this streaked pattern; their plumage is more uniform and dark, with the only contrast being the chestnut wings.
• Immature/juvenile Violet-backed Starling: Not explicitly described, but likely similar to adult female with streaked appearance. Chestnut-winged Starling juveniles are not detailed, but no evidence suggests they show strong streaking or white underparts.
• Wing pattern in flight: No specific notes for either species, but the chestnut coloration in Chestnut-winged is likely visible in flight, while Violet-backed shows either violet gloss (male) or streaked brown (female/immature) without chestnut tones.

Violet-backed Starling tends to feed high in the canopy, rarely coming to the ground, and may sally out for insects like a flycatcher [wikipedia]. Chestnut-winged Starling's foraging behavior is not described in detail, but it is generally typical of starlings. Both nest in tree cavities or crevices, but this is not a field mark. Behavior is not a strong separator, though Violet-backed's canopy preference may be a subtle clue.

Violet-backed Starling is found at woodland and savannah forest edges across sub-Saharan Africa [wikipedia]. Chestnut-winged Starling is a species of the African tropical rainforest [wikipedia]. Thus, Violet-backed is more likely at drier, open woodland edges, while Chestnut-winged is expected in humid, dense rainforest. Overlap is possible at forest margins, but habitat can be a useful supporting clue.