Slovenia has some of the most varied and best bird watching in central Europe with more than 376 species being spotted, of which only 219 are breeders. The Julian Alps are noted as an especially important habitat and provide excellent facilities for keen watchers. It should be possible to encounter up to 10 species of Owl in Slovenia (finding them might be another matter although I have seen 3 Pygmy owls on a walk to Vrtraska Sleme) - several of which are not found in the UK:

• Scops Owl
• Little Owl
• Pygmy Owl
• Long-eared Owl
• Short-eared Owl (Winter)
• Barn Owl
• Tawny Owl
• Eagle Owl
• Ural Owl
• Tengmalms Owl

Also the Middle-spotted Woodpecker creates great interest throughout Slovenia - this would be a good one to confirm for interest from birders.  Difficult to find though.

The bird list for Skocjanski Zatok includes several species of interest to UK birders - particularly:

• White & Black Stork
• Pygmy Cormorant (very few reliable sites for this bird)
• Lesser Grey Shrike

In Summer - you can add:

• Melodious Warbler
• Icterine Warbler
• Moustached Warbler
• Savi's Warbler
• Zitting Cisticola
• Thrush Nightingale

From “The Good Bird Guide” by Keith Marsh:

Triglav National Park (nearest of these 6 sites to the house)
840km squared. Slovenia’s only National Park, covering limestone mountains of the Julian Alps reaching more than 2680m. Habitats include bare mountains, and alpine meadows, coniferous, mixed and deciduous woodland on the slopes, and Mediterranean scrub in the lower areas.
Birds include Northern Goshawk, Golden Eagle, and montane species such as Ptarmigan, Rock Partridge, Alpine Accentor, Wallcreeper, Choughs (both species), and Snowfinch. The forested areas support Capercaillie, Hazel & Black Grouse; Black, Grey-headed and Three-toed Woodpeckers, and many passerines. Citril Finch is very rare, but possible at Triglav. The nearest major town is Bled to the East .

Karst Regional Park (SW Corner)
Limestone hills famous for geological features including canyons, sink holes and caves. Forest and scrub with interesting breeding birds – Eurasian Scops Owl, Wryneck, Crested Tit, Short-toed Treecreeper and Rock Bunting in Summer. Postojna is a good base and can be reached by road from Trieste and Ljubljana

Kocevje (SE Corner)
Forested hills of Dinaric plateau above Kocevje are little known ornithologically but cover a vast largely uninhabited area. Ural and Eurasian Scops Owl occur in small numbers and the only White-tailed Eagles in Slovenia are found here. Also present are Wryneck, Black & Grey-headed Woodpeckers, Ring Ouzel, Collared Flycatcher, Crested Tit and Short-toed Treecreeper. Kocevje is easily accessible by road.

Krakovski Forest
Important virtually undisturbed lowland forest in eastern Slovenia; part of which is a reserve. The avifauna is little known.
Breeders include Black and White Storks, Lesser Spotted Eagle (only site in Slovenia), Black and Middle Spotted Woodpeckers, and Collared Flycatcher.
Located east of Ljubljana in the central Krsko Valley.

Lake Cerknica
Reed-fringed lake situated south of Ljubljana near the town of Bakek.
Breeding Little Bittern, Ferruginous Duck, Spotted & Little Crakes, and Corncrakes. White-tailed Eagle and White-winged Black Tern are visitors.

Ljubljansko Moor
150km squared of mainly agricultural land. In places however, it still has some original mire with flooded meadows and wet woodland. The most important Corncrake site in Slovenia. It also supports small numbers of Little Bittern, Lesser Kestrel, Wryneck and Barred Warbler. Black Stork may still occur. Located on the southern side of Ljubljana.