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

Mimus gilvus

Coereba flaveola

Thraupis palmarum

Amazona amazonica

Saucerottia tobaci

Psarocolius decumanus

Turdus nudigenis

Tachyphonus rufus

Pitangus sulphuratus

Thraupis episcopus

Thamnophilus doliatus

Tyrannus melancholicus
The reference database has no regions filed under Trinidad & Tobago.
The field guide covers Trinidad & Tobago on the map, but none of its species have an entry written for them yet.