Tolmomyias assimilis
Silhouette: Emily Willoughby · PhyloPic
In 3 days ~20% in a week ~30%
The yellow-margined flatbill or Zimmer's flatbill (Tolmomyias assimilis) is a species of bird in the tyrant flycatcher family Tyrannidae. It is found in every mainland South American country except Argentina, Chile, Paraguay, and Uruguay.
The yellow-margined flatbill has a complicated taxonomic history. It was originally described as Rhynchocyclus assimilis. In the early twentieth century it was treated as a subspecies of the yellow-olive flatbill (now T. sulphurescens) but was separated by most authors starting in about 1940. As of 2025 it has eight subspecies. However, what is now the yellow-winged flatbill (T. flavotectus) was previously a ninth subspecies. It was separated starting in 2016 but the process continued until 2024. Confusingly, for a time T. flavotectus was called the yellow-margined flatbill.
The eight subspecies of the yellow-margined flatbill are: The... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Utría National Natural Park | 🇨🇴 Colombia | |
| 2 | Soberanía National Park | 🇵🇦 Panama | |
| 3 | Darién National Park | 🇵🇦 Panama | |
| 4 | Yasuní National Park | 🇪🇨 Ecuador | |
| 5 | Chagres National Park | 🇵🇦 Panama | |
| 6 | Parque Natural Metropolitano | 🇵🇦 Panama | |
| 7 | Brownsberg Nature Park | 🇸🇷 Suriname | |
| 8 | Tambopata National Reserve | 🇵🇪 Peru | |
| 9 | Gandoca-Manzanillo Wildlife Refuge | 🇨🇷 Costa Rica | |
| 10 | San Lorenzo Protected Forest | 🇵🇦 Panama | |
| 11 | Bastimentos Island National Marine Park | 🇵🇦 Panama | |
| 12 | Sierra de la Macarena National Park | 🇨🇴 Colombia | |
| 13 | Amboró National Park | 🇧🇴 Bolivia | |
| 14 | Manu National Park | 🇵🇪 Peru | |
| 15 | Braulio Carrillo National Park | 🇨🇷 Costa Rica | |
| 16 | La Amistad International Park (Panama) | 🇵🇦 Panama | |
| 17 | Tortuguero National Park | 🇨🇷 Costa Rica | |
| 18 | Amacayacu National Natural Park | 🇨🇴 Colombia | |
| 19 | Farallones de Cali National Natural Park | 🇨🇴 Colombia | |
| 20 | Podocarpus National Park | 🇪🇨 Ecuador | |
| 21 | Arenal Volcano National Park | 🇨🇷 Costa Rica | |
| 22 | Tapantí-Macizo de la Muerte National Park | 🇨🇷 Costa Rica |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Panama City | 🇵🇦 Panama |
With luck
About 10% of wildlife watchers report a Yellow-margined Flycatcher sighting in Yasuní National Park on a given day, based on 162 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 245th most-seen of the 533 birds we can rate there. Over three days the chance rises to about 20%, and over a week to about 30%, if each day is a fresh chance.
January–March, July–August and October
In those months about 10% of wildlife watchers report a Yellow-margined Flycatcher in Yasuní National Park on a given day, against under 5% in April–June, September and November–December, the lowest months.
Between 8 and 11 am
Across all the parks we cover, that three-hour window holds the most Yellow-margined Flycatcher sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Among the best
Of the 22 parks where we can rate Yellow-margined Flycatcher sightings, Yasuní National Park ranks 4th at about 10%, level with the leaders once rounded. The best odds are in Utría National Natural Park (Colombia, about 10%), Soberanía National Park (Panama, about 10%) and Darién National Park (Panama, about 10%).
Same genus: Tolmomyias
The closest relatives of the Yellow-margined Flycatcher that you can see in Yasuní National Park (genus Tolmomyias, Tolmomyias Flatbills) are Gray-crowned Flycatcher (about 10%) and Yellow-breasted Flycatcher (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Yellow-margined Flycatcher is recorded against all the birds logged in Yasuní National Park (162 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
