Orange-eared tanager 
Orange-eyed flatbill 
Orange-fronted plushcrown 
Orange-fronted yellow finch 
Orange-headed Tanager 
Orange-headed thrush 
Orange-winged pytilia 
Orchard oriole 
Oriental magpie 
Oriental Magpie-Robin 
Oriental White-eye 
Orinoco softtail 
Oriole blackbird 
Ornate flycatcher 
Ornate stipplethroat 
Ornate sunbird 
Ortolan bunting 
Oustalet's Sunbird 
Ovenbird 
Oxapampa Antpitta 
Pacific antwren 
Pacific elaenia 
Pacific Hornero 
Pacific swallow