Olive-striped flycatcher 
Olive-winged bulbul 
One-colored Becard 
Opal-crowned Tanager 
Opal-rumped tanager 
Orange ground thrush 
Orange minivet 
Orange River white-eye 
Orange-backed Troupial 
Orange-bellied Euphonia 
Orange-bellied flowerpecker 
Orange-bellied leafbird 
Orange-billed Babbler 
Orange-billed nightingale-thrush 
Orange-billed Sparrow 
Orange-breasted bushshrike 
Orange-breasted Fruiteater 
Orange-breasted Sunbird 
Orange-breasted waxbill 
Orange-cheeked waxbill 
Orange-collared manakin 
Orange-crested Manakin 
Orange-crowned oriole 
Orange-crowned warbler