- Ocellated Piculet
- Ocellated Turkey
- Olivaceous Elaenia
- Olive-backed Oriole
- Olive-headed Lorikeet
- Olive Bee-eater
- Orange-backed Troupial
- Orange-bellied Fruit Dove
- Orange-breasted Falcon
- Orange-footed Scrubfowl
- Orange-fronted Fruit Dove
- Orange-fronted Parakeet
- Orange-spotted Bulbul
- Orange-winged Amazon
- Oriental Darter
- Oriental Dollarbird
- Oriental Magpie-Robin
- Oriental Pied Hornbill
- Oriental Stork
- Orinoco Goose
- Ortolan Bunting
- Osprey
- Osprey (cristatus)