アマゾンアリモズ 対 ボリビアコビトドリモドキ

The most reliable field mark to separate Amazonian Antshrike from Yungas Tody-Tyrant is overall structure: the antshrike is much larger and heavier-bodied, with a thick, hooked bill and strong, contrasting sexual dimorphism, while the tody-tyrant is tiny, compact, and has a flat, broad-based bill. In all plumages, the antshrike shows bold white spots and edges on the wings and tail (especially in males), while the tody-tyrant's wings are dark olive with only faint, indistinct yellowish wing bars. Females and immature antshrikes are rich rufous or olive below, never grayish-olive like the tody-tyrant. If you see a small, bushy-crested, olive bird with a pale belly and subtle wing bars, it's the tody-tyrant; a larger, heavy-billed, boldly patterned bird is the antshrike.

1. Size and structure: The antshrike is nearly twice as heavy as the tody-tyrant, with a robust, broad-chested body and a thick, hooked bill. The tody-tyrant is tiny, compact, and has a flat, wide-based bill. If the bird looks small and delicate, it's likely the tody-tyrant.
2. Bill shape: Amazonian Antshrike's bill is stout, deep, and hooked at the tip (shrike-like), ideal for tearing insects. Yungas Tody-Tyrant's bill is flat and broad at the base, more suited to flycatching.
3. Sexual dimorphism: Only the antshrike shows strong differences between sexes: males are black/gray with bold white markings, females are rufous/olive. Tody-tyrant sexes look alike.
4. Crown and crest: Tody-tyrant has a dark olive-green crown with a short, bushy crest (often raised). Antshrike males have a black or gray crown, females a bright rufous crown, but no bushy crest.
5. Wing pattern: Antshrike (especially males) has bold white spots and edges on the wings and tail, visible both perched and in flight. Tody-tyrant has only faint, yellowish-olive wing bars—never any white.
6. Tail pattern: Antshrike's tail is black with white tips and spots (males) or browner with pale edges (females). Tody-tyrant's tail is plain dark olive with no pale tips or spots.
7. Underparts: Antshrike males are gray below; females are bright yellowish red-brown to buff. Tody-tyrant is grayish olive with faint whitish streaks and a clear yellowish-white belly—never rufous or buff like female antshrike.
8. Face pattern: Tody-tyrant has grayish buff lores on an olive face; antshrike males have a black/gray face, females a rufous/olive face.
9. Eye color: Tody-tyrant has a pale yellow iris; antshrike's eye color is not specified but is not a known field mark.
10. Leg color: Tody-tyrant has pinkish gray to pinkish legs and feet; antshrike's leg color is not specified.
11. Habitat and range: If in the Amazonian lowlands, expect antshrike; if in the Yungas of Bolivia/Peru, expect tody-tyrant.
12. Behavior: Antshrike is methodical, often in pairs or mixed flocks, sometimes following ants. Tody-tyrant is likely more active and flycatcher-like.
13. No white in wings/tail: If you see any white in the wings or tail, it's not the tody-tyrant.
14. No sexual dimorphism: If both sexes look alike, it's the tody-tyrant; if male/female look very different, it's the antshrike.
15. Plumage pitfalls: Female antshrikes can be confused with tody-tyrant due to olive/rufous tones, but always check for size, bill shape, and presence/absence of bold white in wings/tail.

Amazonian Antshrike is significantly larger and heavier, measuring 14–15 cm in length and weighing 17–21 g. In contrast, Yungas Tody-Tyrant is much smaller at about 11 cm and only 7 g. The antshrike appears robust and broad-chested, while the tody-tyrant is petite, compact, and almost half the antshrike's mass. This size gap is obvious in the field, especially when seen side by side or compared to known reference species.

• Juvenile/immature plumage: No specific notes on immature wing patterns for either species, but adult plumage is strongly diagnostic.
• Amazonian Antshrike: Adult males are black and gray above with bold white spots and edges on the wings and tail; females are bright rufous on the crown and underparts, with deep olive backs and browner wings/tail edged pale olive. Subspecies vary, but all show some combination of dark upperparts and contrasting pale or rufous underparts, with white in the wings/tail.
• Yungas Tody-Tyrant: Both sexes are similar. The crown is dark olive-green with a short, bushy crest; face is olive-green with grayish buff lores. Wings and tail are dark olive with two faint yellowish-olive wing bars. Underparts are grayish olive with faint whitish streaks and a clear yellowish-white belly. No bold white in wings or tail, and no sexual dimorphism.
• Key contrast: Antshrike (especially males) always shows bold white spots/edges on wings and tail, and strong sexual dimorphism; tody-tyrant is uniformly olive and grayish, with only subtle wing bars and no white in the wings/tail.

Amazonian Antshrike typically forages singly or in pairs, moving methodically through thickets and vine tangles, often joining mixed-species flocks or occasionally following army ants. It hops and lunges from perches, gleaning insects from foliage. Yungas Tody-Tyrant's behavior is not detailed here, but as a small tyrant flycatcher, it is likely to make quick sallies from low perches and show more flycatcher-like, agile movements. The antshrike's heavier build and slower, deliberate movements contrast with the likely more active, flitty behavior of the tody-tyrant.

Amazonian Antshrike is widespread in lowland Amazonian forests across most of South America (except the southern cone), favoring dense thickets, vine tangles, and forest understory. Yungas Tody-Tyrant is restricted to the Yungas region of Bolivia and Peru, a montane forest habitat. Thus, range and habitat can be a strong clue: if you are in the Amazonian lowlands, expect antshrike; in humid Andean foothills (Yungas), expect tody-tyrant.