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

Corvus cornix

Larus cachinnans

Passer montanus

Haliaeetus albicilla

Dendrocopos major

Emberiza citrinella

Picus viridis

Phasianus colchicus

Coccothraustes coccothraustes

Ficedula albicollis

Milvus milvus

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