- Oasis Hummingbird
- Ocellated Piculet
- Ocellated Tapaculo
- Ocellated Turkey
- Ochraceous-breasted Flycatcher
- Ochre-bellied Flycatcher
- Ochre-breasted Antpitta
- Ochre-breasted Tanager
- Ochre-collared Piculet
- Oilbird
- Oleaginous Hemispingus
- Olivaceous Thornbill
- Olivaceous Woodcreeper
- Olive-backed Euphonia
- Olive-backed Pipit
- Olive-crowned Yellowthroat
- Olive-striped Flycatcher
- Olive-throated Parakeet
- Olive Oropendola
- Orange-bellied Euphonia
- Orange-billed Nightingale-Thrush
- Orange-billed Sparrow
- Orange-breasted Falcon
- Orange-breasted Fruiteater
- Orange-chinned Parakeet
- Orange-collared Manakin
- Orange-crowned Oriole
- Orange-eared Tanager
- Orchard Oriole
- Orinoco Goose
- Ornate Flycatcher
- Ornate Tinamou
- Ovenbird