- Ochraceous Wren
- Ochre-bellied Flycatcher
- Ochre-breasted Antpitta
- Oilbird
- Olivaceous Elaenia
- Olivaceous Piculet
- Olive-backed Woodcreeper
- Olive-bellied Sunbird
- Olive Bee-eater
- Olive Oropendola
- Olive Sunbird
- Opal-crowned Tanager
- Orange-backed Troupial
- Orange-bellied Euphonia
- Orange-bellied Leafbird
- Orange-bellied Parrot
- Orange-billed Babbler
- Orange-breasted Fruiteater
- Orange-breasted Trogon
- Orange-cheeked Waxbill
- Orange-chinned Parakeet
- Orange-crested Manakin
- Orange-crowned Euphonia
- Orange-crowned Oriole
- Orange-eared Tanager
- Orange-fronted Barbet
- Orange-winged Amazon
- Orange Minivet
- Oriental Darter
- Oriental Dollarbird
- Oriental Magpie-Robin
- Oriental Pied Hornbill
- Oriental Pratincole
- Oriental Skylark
- Oriole Blackbird
- Ornate Flycatcher
- Ornate Sunbird
- Osprey
- Ovenbird