Tolmomyias assimilis
Silhouette: Emily Willoughby · PhyloPic
In 3 days <5%
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 |
Rare
Under 5% of wildlife watchers report a Yellow-margined Flycatcher sighting in Arenal Volcano National Park on a given day, based on 25 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 442nd most-seen of the 503 birds we can rate there. Over three days the chance rises to under 5%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Yellow-margined Flycatcher in Arenal Volcano National Park on a given day, so our monthly data shows no clear season.
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.
21st of 22
Of the 22 parks where we can rate Yellow-margined Flycatcher sightings, Arenal Volcano National Park ranks 21st at under 5%. 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%).
GBIF citizen-science records
It is estimated from how often the Yellow-margined Flycatcher is recorded against all the birds logged in Arenal Volcano National Park (25 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.
