- Ochre-breasted Antpitta
- Olivaceous Woodcreeper
- Olive-backed Euphonia
- Olive-throated Parakeet
- Olive Finch
- One-colored Becard
- Opal-rumped Tanager
- Orange-backed Troupial
- Orange-bellied Euphonia
- Orange-bellied Fruit Dove
- Orange-breasted Waxbill
- Orange-cheeked Waxbill
- Orange-chinned Parakeet
- Orange-crowned Oriole
- Orange-fronted Fruit Dove
- Orange-fronted Parakeet
- Orange-winged Amazon
- Orchard Oriole
- Oriental Darter
- Oriental Magpie-Robin
- Orinoco Saltator
- Ornate Melidectes
- Ortolan Bunting
- Osprey