- Olivaceous Woodcreeper
- Olive-backed Pipit
- Olive-bellied Sunbird
- Olive Bee-eater
- Orange-backed Troupial
- Orange-billed Babbler
- Orange-breasted Green Pigeon
- Orange-breasted Waxbill
- Orange-crowned Warbler
- Orange-fronted Yellow Finch
- Orange-headed Thrush
- Orange Minivet
- Orange Weaver
- Oriental Darter
- Oriental Magpie-Robin
- Oriental Pratincole
- Oriental Scops Owl
- Orinoco Goose
- Oriole Finch
- Ornate Tinamou
- Ortolan Bunting
- Osprey
- Ovambo Sparrowhawk