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

Larus fuscus

Sturnus unicolor

Curruca melanocephala

Larus michahellis

Serinus serinus

Turdus merula

Cisticola juncidis

Saxicola rubicola

Sylvia atricapilla

Phoenicurus ochruros

Motacilla alba

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