I'm now back from a 5-days non-birding trip around Slovenia. The visited areas were: Bela Krajina (with Novo Mesto), Štajerska (Celje, Ptuj, Maribor), Prekmurje, Koroška (+ Kamniško Savinske Alpe). So here's a short list of the few interesting wildlife I've seen (mostly from the drive with the bus):
Buzzard - literally tons of them!
Reed Warbler - some singing in the Drava's reedbeds
Crested Lark - Štajerska
Common Tern - at Ptuj
Common Quail - 1 singing at dusk in the fields near Ptuj
Sand Martin - Štajerska
White Stork - both in the Prekmurje and Primorska region
Black Stork - 1 stunning bird in the Gornji Grad - Kamnik area; perching on a high coniferous tree just by the roadside.
Banded Demoiselle - quite common in the north and east