- Oasis Hummingbird
- Ochraceous Bulbul
- Ochraceous Wren
- Ochre-breasted Antpitta
- Olive-backed Euphonia
- Olive-bellied Sunbird
- Olive-grey Saltator
- Olive-winged Bulbul
- Olive Thrush
- Orange-bellied Flowerpecker
- Orange-billed Nightingale-Thrush
- Orange-billed Sparrow
- Orange-breasted Bushshrike
- Orange-breasted Sunbird
- Orange-cheeked Waxbill
- Orange-chinned Parakeet
- Orange-crowned Oriole
- Orange-fronted Parakeet
- Orange River White-eye
- Orange Weaver
- Oriental Bay Owl
- Oriental Darter
- Oriental Dollarbird
- Oriental Magpie-Robin
- Oriental Pied Hornbill
- Oriental Reed Warbler
- Ornate Sunbird
- Ortolan Bunting
- Osprey
- Ovenbird