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

Pycnonotus barbatus

Lamprotornis purpuroptera

Colius striatus

Passer griseus

Bostrychia hagedash

Camaroptera brachyura

Bycanistes subcylindricus

Crinifer zonurus

Laniarius erythrogaster

Streptopelia semitorquata

Turdus pelios

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