Family Tyrant-flycatchers (Tyrannidae)

Least Concern

Yellow-margined Flatbill (Tolmomyias assimilis)


French: Tyranneau à miroir German: Flügelspiegel-Breitschnabeltyrann Spanish: Picoplano aliamarillo común
Other common names: Zimmer's Flatbill, Yellow-margined Flycatcher

Rhynchocyclus assimilis


, 1868,

Borba, Brazil


Until recently considered conspecific with T. flavotectus (see below). Race sucunduri newly described as species#R, most closely related to races assimilis, calamae and paraensis, differing in its darker and more uniformly lead-grey crown (1); slightly darker green back (1); more widely modulated notes in loudsong (2)#R; and hybrid zone with assimilis/calamae in S of range (zone presumed narrow; 2); thus, on current evidence, it falls just short of species status, although new study may validate it. Other races show subtle variations in crown, breast and belly colours (breast becoming slightly darker in anticlockwise direction from the Guianas and NE Brazil back towards E Brazil S of Amazon; crown colour shows similar but slightly discordant pattern); further study needed on taxonomic limits within these races, including vocalizations, as songs of neglectus and examinatus N of Amazon are relatively distinctive vs those of taxa S of Amazon. Eight subspecies recognized.

What do (1) and (2) mean? Learn more about the scoring system.
Subspecies and Distribution
  • T. a. neglectus J. T. Zimmer, 1939 – E Colombia (Vichada to Vaupés), SW Venezuela (Amazonas, NW Bolívar) and NW Brazil (R Negro region of N Amazonas).
  • T. a. examinatus (C. Chubb, 1920) – SE Venezuela (E & S Bolívar), the Guianas and NE Brazil (N bank of lower Amazon in N Pará and Amapá).
  • T. a. obscuriceps J. T. Zimmer, 1939 – SE Colombia (W Meta to Putumayo) S to NE Ecuador and NE Peru (E Loreto N of Amazon).
  • T. a. clarus J. T. Zimmer, 1939 – Peru (Amazonas, from just N of R Marañón, S to N Puno).
  • T. a. assimilis (Pelzeln, 1868) – Yellow-margined Flatbill – C Brazil S of middle Amazon (from Tefé, in C Amazonas, E to R Tapajós, in W Pará).
  • T. a. paraensis J. T. Zimmer, 1939 – NE Brazil (E Pará, NW Maranhão, S to N Mato Grosso in Alta Floresta#R).
  • T. a. calamae J. T. Zimmer, 1939 – SW Brazil (SE Amazonas, Rondônia and N Mato Grosso in Serra dos Caiabis#R) and N Bolivia.
  • T. a. sucunduri Whitney et al., 2013 – Sucunduri Flatbill – C Amazonian Brazil S of Amazon, from right bank of R Canumã and R Sucunduri to left bank of lower Tapajós.
  • Descriptive notes

    13–13·5 cm; 12–17·5 g. Big-headed, with dull white “spectacles”, narrow white eyering broken in front. Nominate race has crown, nape and... read more


    Song a leisurely series of 3–5 nasal buzzy whistles, ascending in pitch and shrill, or... read more


    Mid-level, subcanopy and edge of humid terra firme, várzea forest, tall... read more

    Food and feeding

    Diet mostly beetles (Coleoptera), worker ants (Hymenoptera), homopteran bugs (leafhoppers); small amounts of fruit (berries) taken. Stomach... read more


    Almost nothing known.



    Status and conservation

    Not globally threatened (Least Concern). Uncommon to locally fairly common; probably often overlooked and status in Surinam has been confused, despite being rather common and... read more

    Recommended citation

    Caballero, I. & Kirwan, G.M. (2019). Yellow-margined Flatbill (Tolmomyias assimilis). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from on 12 December 2019).