Tolmomyias assimilis
Silhouette: Emily Willoughby · PhyloPic
In 3 days ~10% 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 |
Rare
Under 5% of wildlife watchers report a Yellow-margined Flycatcher sighting in Gandoca-Manzanillo Wildlife Refuge on a given day, based on 63 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 193rd most-seen of the 329 birds we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
June and July
In those months about 20% of wildlife watchers report a Yellow-margined Flycatcher in Gandoca-Manzanillo Wildlife Refuge on a given day, against under 5% in August–September and November–May, the lowest months. Those are among Gandoca-Manzanillo Wildlife Refuge's wettest months, with about 480 mm of rain a month against 140 mm in March.
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.
9th of 22
Of the 22 parks where we can rate Yellow-margined Flycatcher sightings, Gandoca-Manzanillo Wildlife Refuge ranks 9th 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 Gandoca-Manzanillo Wildlife Refuge (63 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.
