
These are species with at least one recorded territory in Ecuador, not a national checklist: a bird list from eBird or Avibase is more complete. The counts follow recording effort as much as wildlife, so a country with more visitors and more naturalists will show more of both.
The species with the most open occurrence records in Ecuador, among those a photograph exists for. Most recorded is not most numerous: it rewards animals that are common, conspicuous and live where people go.

Zonotrichia capensis

Thraupis episcopus

Pygochelidon cyanoleuca

Turdus fuscater

Euphonia xanthogaster

Tyrannus melancholicus

Ramphocelus flammigerus

Tangara arthus

Colibri coruscans

Myioborus miniatus

Amazilia tzacatl

Psarocolius angustifrons
The reference database has no regions filed under Ecuador.
The field guide covers Ecuador on the map, but none of its species have an entry written for them yet.