- Ochraceous Bulbul
- Oilbird
- Olivaceous Piculet
- Olive-backed Pipit
- Olive-bellied Sunbird
- Olive-grey Saltator
- Olive-naped Weaver
- Olive Bee-eater
- Olive Long-tailed Cuckoo
- Orange-billed Sparrow
- Orange-breasted Bushshrike
- Orange-breasted Trogon
- Orange-cheeked Waxbill
- Orange-chinned Parakeet
- Orange-headed Thrush
- Orange Weaver
- Oriental Cuckoo
- Oriental Darter
- Oriental Magpie-Robin
- Oriental Pied Hornbill
- Oriental Plover
- Oriental Reed Warbler
- Oriental Scops Owl
- Oriental Turtle Dove
- Ortolan Bunting
- Osprey
- Ovenbird