| Common Name | Scientific name |
|---|---|
| Orangequit | Euneornis campestris |
| Orange-winged Parrot | Amazona amazonica |
| Orange-fronted Parakeet | Eupsittula canicularis |
| Orange-flanked Bush Robin | Tarsiger cyanurus |
| Orange-crowned Warbler | Oreothlypis celata |
| Orange-crowned Oriole | Icterus auricapillus |
| Orange-collared Manakin | Manacus aurantiacus |
| Orange-chinned Parakeet | Brotogeris jugularis |
| Orange-cheeked Waxbill | Estrilda melpoda |
| Orange-breasted Falcon | Falco deiroleucus |
| Orange-breasted Bunting | Passerina leclancherii |
| Orange-billed Sparrow | Arremon aurantiirostris |
| Orange-billed Nightingale-Thrush | Catharus aurantiirostris |
| Orange-bellied Trogon | Trogon aurantiiventris |
| Orange-bellied Euphonia | Euphonia xanthogaster |
| Orange Oriole | Icterus auratus |
| Orange Bishop | Euplectes franciscanus |
| One-colored Becard | Pachyramphus homochrous |
| Omao | Myadestes obscurus |
| Olomao | Myadestes lanaiensis |
| Olive-tree Warbler | Hippolais olivetorum |
| Olive-throated Parakeet | Eupsittula nana |
| Olive-striped Flycatcher | Mionectes olivaceus |
| Olive-sided Flycatcher | Contopus cooperi |
| Olive-crowned Yellowthroat | Geothlypis semiflava |
RingBase adheres to EURING codes.
