| Common Name | Scientific name |
|---|---|
| Orchard Oriole | Icterus spurius |
| Orejero - Elephant-ear tree | Enterolobium cyclocarpum |
| Oriental Cuckoo | Cuculus optatus |
| Oriental Greenfinch | Chloris sinica |
| Oriental Plover | Charadrius veredus |
| Oriental Pratincole | Glareola maldivarum |
| Oriental Scops-Owl | Otus sunia |
| Oriental Skylark | Alauda gulgula |
| Oriental Stork | Ciconia boyciana |
| Oriental Turtle-Dove | Streptopelia orientalis |
| Oriente Warbler | Teretistris fornsi |
| Orinoco Goose | Neochen jubata |
| Ornate Hawk-Eagle | Spizaetus ornatus |
| Ortolan Bunting | Emberiza hortulana |
| Osprey | Pandion haliaetus |
| Ou | Psittirostra psittacea |
| Ovenbird | Seiurus aurocapilla |
| Pacific Antwren | Myrmotherula pacifica |
| Pacific Black Duck | Anas superciliosa |
| Pacific Golden Plover | Pluvialis fulva |
| Pacific Loon | Gavia pacifica |
| Pacific Parakeet | Psittacara strenuus |
| Pacific Screech-Owl | Megascops cooperi |
| Pacific Swift | Apus pacificus |
| Pacific Wren | Troglodytes pacificus |
RingBase adheres to EURING codes.
