コビトドリモドキ 対 ギンバラコビトドリモドキ

要点

The most reliable field mark to separate Drab-breasted Pygmy-Tyrant from Pearly-vented Tody-Tyrant is the presence of bold wing bars and a much paler, whiter underpart in the latter, versus the plain, olive-toned wings and dull grayish-pinkish breast of the former. Both are small, olive-to-brownish tyrannulets, but Drab-breasted Pygmy-Tyrant is plainer overall with a darker olive crown and little contrast, while Pearly-vented Tody-Tyrant shows a grayish crown, two clear wing bars, and a whiter belly. In the field, look for the subtle but diagnostic differences in wing pattern and underpart color, especially when birds are perched or briefly flick their wings. Both species overlap in parts of southern South America, so careful attention to these plumage details is essential.

識別のコツ

1. Wing pattern is key: Pearly-vented Tody-Tyrant always shows two pale wing bars on dusky wings, visible even at a distance or in brief wing flicks; Drab-breasted Pygmy-Tyrant's wings are plain olive with at most faint pale edging on the innermost secondaries, never true wing bars. This is the most reliable mark in all ages and seasons.
2. Crown color: Drab-breasted Pygmy-Tyrant has a dark olive-green crown blending into the back; Pearly-vented Tody-Tyrant has a gray (or brownish-gray in some subspecies) crown that contrasts with the back, especially in nominate and northern forms.
3. Underparts: Drab-breasted Pygmy-Tyrant has a dull gray breast with a pinkish or purplish tinge and a faint white crescent separating it from the whitish belly; Pearly-vented Tody-Tyrant is much whiter below, with only faint grayish streaking and no pinkish wash.
4. Facial pattern: Both have a white eye-ring and pale lores, but Drab-breasted Pygmy-Tyrant's face is olive overall, while Pearly-vented Tody-Tyrant's face is grayer and more contrasting, especially around the eye.
5. Back and rump: Drab-breasted Pygmy-Tyrant is plain dark olive-green above; Pearly-vented Tody-Tyrant is drab grayish brown to brownish olive, sometimes with a slight olive or buff tinge depending on subspecies, but always less uniformly olive than Drab-breasted.
6. Tail color: Both have dusky or olive tails, but this is not a strong separator.
7. Bill and legs: Both have a pale lower mandible and grayish to pinkish legs, not a reliable field mark.
8. Iris color: Drab-breasted Pygmy-Tyrant has a reddish brown iris; Pearly-vented Tody-Tyrant has a pale iris. This may help at close range in good light.
9. Size: Both are tiny, but Drab-breasted Pygmy-Tyrant averages slightly heavier (10 g vs. 7–10 g), not useful in the field.
10. Habitat context: In bamboo or dense forest undergrowth, suspect Drab-breasted Pygmy-Tyrant; in open scrub, pastures, or woodland edge, Pearly-vented Tody-Tyrant is more likely, but ranges overlap in southern Brazil, Argentina, and Paraguay.
11. Subspecies variation: Pearly-vented Tody-Tyrant has several subspecies with minor plumage differences (e.g., crown and belly color), but all show wing bars and a paler belly than Drab-breasted Pygmy-Tyrant.
12. No strong seasonal or sex differences: Both species have similar plumage year-round and between sexes, so all marks apply in all seasons.
13. Juvenile/immature plumage: No distinctive juvenile wing or flight patterns are described for either species, so rely on adult marks for all ages.
14. Voice: Not described in the sources, so not a safe separator here.
15. Pitfalls: Drab-breasted Pygmy-Tyrant can appear slightly paler below in bright light, but never shows true wing bars or a gray crown; Pearly-vented Tody-Tyrant can look drabber in worn plumage, but always retains some contrast in the wings and underparts.

大きさ

Both species are tiny flycatchers, with Drab-breasted Pygmy-Tyrant averaging about 11 cm in length and 10 g in mass, and Pearly-vented Tody-Tyrant very similar in length (10–11 cm) but slightly lighter (7–10 g). In hand or at close range, Drab-breasted Pygmy-Tyrant may appear marginally bulkier, but this is not a reliable field mark; both are among the smallest tyrant-flycatchers and size overlap is extensive.

羽色

There are no age-specific wing patterns described for either species, so focus is on adult and general plumage. Drab-breasted Pygmy-Tyrant is very plain: the crown, back, wings, and tail are all dark olive-green with little contrast, and the wings lack any obvious bars or panels, though the innermost secondaries may have faint pale edges. The face has a white spot above the lores and a white eye-ring, but otherwise is olive. The throat and breast are dull gray with a pinkish or purplish tinge, separated by a faint white crescent, and the belly is whitish with a yellowish tinge on the crissum. Pearly-vented Tody-Tyrant, in contrast, has a gray crown (not olive), a grayish-brown to brownish-olive back, and crucially, dusky wings with buff to yellowish edges on the flight feathers and two clear wing bars formed by pale tips to the coverts. Its underparts are much paler—white with faint grayish streaking—and the face is grayer, with a whitish eye-ring and lores. Subspecies variation exists, but all forms show more contrast and wing pattern than Drab-breasted Pygmy-Tyrant.

行動

Behavior is not strongly diagnostic between these two species. Both are typical small tyrannulets, often seen perched low or mid-level in dense vegetation, making short sallies for insects. Drab-breasted Pygmy-Tyrant is sometimes associated with bamboo, while Pearly-vented Tody-Tyrant is more often in open, shrubby, or edge habitats. Both may flick wings and tails, but this is not a reliable separator.

生息環境

Drab-breasted Pygmy-Tyrant is more restricted in range, found in Argentina, Brazil, and Paraguay, and is often associated with bamboo or dense forest undergrowth. Pearly-vented Tody-Tyrant is much more widespread, occurring in nearly all mainland South American countries except Chile, Ecuador, French Guiana, and Suriname, and is found in a wide variety of shrubby, dry, and edge habitats, including arid scrub, pastures, and woodland edges. If seen in very dry, open, or scrubby areas, Pearly-vented Tody-Tyrant is more likely, while Drab-breasted Pygmy-Tyrant prefers moister, denser, or bamboo-rich habitats.