
These are species with at least one recorded territory in Panama, 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 Panama, among those a photograph exists for. Most recorded is not most numerous: it rewards animals that are common, conspicuous and live where people go.

Thraupis episcopus

Tyrannus melancholicus

Turdus grayi

Melanerpes rubricapillus

Amazilia tzacatl

Coragyps atratus

Brotogeris jugularis

Sporophila corvina

Columbina talpacoti

Thraupis palmarum

Ramphocelus dimidiatus

Ramphastos sulfuratus
Improbable bill, croaking calls above the canopy.
The reference database has no regions filed under Panama.
The field guide covers Panama on the map, but none of its species have an entry written for them yet.