| Common Name | Scientific name |
|---|---|
| Oahu Elepaio | Chasiempis ibidis |
| Oahu Nukupuu | Hemignathus lucidus |
| Oahu Oo | Moho apicalis |
| Oak Titmouse | Baeolophus inornatus |
| Oaxaca Sparrow | Aimophila notosticta |
| Ocellated Antbird | Phaenostictus mcleannani |
| Ocellated Crake | Micropygia schomburgkii |
| Ocellated Poorwill | Nyctiphrynus ocellatus |
| Ocellated Quail | Cyrtonyx ocellatus |
| Ocellated Thrasher | Toxostoma ocellatum |
| Ocellated Turkey | Meleagris ocellata |
| Ochraceous Pewee | Contopus ochraceus |
| Ochraceous Wren | Troglodytes ochraceus |
| Ochre-bellied Flycatcher | Mionectes oleagineus |
| Ochre-breasted Antpitta | Grallaricula flavirostris |
| Oilbird | Steatornis caripensis |
| Olivaceous Flatbill | Rhynchocyclus olivaceus |
| Olivaceous Piculet | Picumnus olivaceus |
| Olivaceous Woodcreeper | Sittasomus griseicapillus |
| Olive Sparrow | Arremonops rufivirgatus |
| Olive Warbler | Peucedramus taeniatus |
| Olive-backed Euphonia | Euphonia gouldi |
| Olive-backed Pipit | Anthus hodgsoni |
| Olive-backed Quail-Dove | Leptotrygon veraguensis |
| Olive-capped Warbler | Setophaga pityophila |
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