Yellow-throated Antwren Myrmotherula ambigua Scientific name definitions

The Yellow-throated Antwren is endemic to far northwestern Amazonia, where it is confined to extreme southwest Venezuela, far-eastern Colombia, and northwest Brazil, and is found in a variety of forest types, all of them growing on white-sand soils. It primarily occurs in the true lowlands, below 500 m, but locally the species ascends to approximately 1100 m on some tepuis. This antwren’s plumage broadly recalls that of the congeneric Sclater’s Antwren (Myrmotherula sclateri), which is found only south of the Amazon, where it appears to be the present species’ ecological counterpart. Very little has been published concerning the Yellow-throated Antwren’s behavior, although it seems to be a constant member of mixed-species foraging flocks in the canopy and subcanopy throughout its range, and these bands frequently also contain Pygmy Antwren (Myrmotherula brachyura).

8–8·5 cm; 7–8 g. Male is black above, streaked white, light yellow interscapular patch, rump greyish, two prominent white wingbars, tail feathers edged white, narrowly tipped white; cheeks whitish, underparts light yellow, black malar streak, some black streaks on sides. Distinguished from very similar M. sclateri by having crown and nape streaks white, rump grey, malar streak less prominent. Female is similar to male, but pale colours on head and breast tawny-buff to buff, inter­scapular patch minimal or absent.

SW Venezuela (S Amazonas), extreme E Colombia (Guainía, Vaupés) and NW Brazil (upper R Negro region E to NC Roraima and S to Jaú).

Canopy and subcanopy of lowland evergreen forest, mostly below 350 m; occasionally to c. 1100 m on sides of tepuis. Found in variety of forest types that occur on white-sand soils, and which have been referred to collectively as “Amazonian caatinga”: these include lower-stature, less floristically diverse forest on purer sandy soils, as well as high-canopied (35 m or more), more diverse forest on mixed soils.

Presumed resident.

Not well known. Feeds on various small insects; probably also on spiders and other arthropods. Usually encountered as closely associated pair-members, and almost always associated with mixed-species canopy flocks of furnariids, tyrant-flycatchers (Tyrannidae), tanagers (Thraupidae) and other insectivores. Often in same flocks as M. brachyura. Roams the highest parts of the canopy, hopping rapidly through smaller branches and terminal foliage, where it perch-gleans prey from leaf (primarily), branch and vine surfaces with darting stabs, and hover-gleans. Also works vine tangles and smaller epiphytes in interior of canopy, occasionally descending to mid-storey along clusters of hanging vines adjacent to trunks. In stunted white-sand forest, regularly feeds as low as 10–15 m, these heights still constituting the canopy and subcanopy. Appears to be the ecological counterpart of M. sclateri.

Loudsong an evenly paced and evenly pitched series like that of M. sclateri, but notes much shorter and downslurred, overall pace much faster (e.g. 8 notes, 4·4 seconds).

Nothing known.

Not globally threatened. Restricted-range species: present in Orinoco-Negro White-sand Forests EBA. Uncommon to fairly common. Its relatively small range does include some large protected areas, e.g. La Neblina National Park and possibly the Alto Orinoco-Casiquiare Biosphere Reserve, in Venezuela, and Pico da Neblina and Jaú National Parks, in Brazil; also vast contiguous areas of intact habitat which are not formally protected, but are under little or no current threat. Regardless of decrees, even areas that are “officially” protected in this region are affected to varying degrees by illegal mining operations; on the broad scale, however, the impact is relatively minimal, and the region in which this species occurs remains one of those that has been least affected by humans in South America.