An exclusive tour of Southwestern Slovenia for a wonderful show of butterflies & summer flowers!
For such a small country, Slovenia is amazingly diverse. After all, the distance from the closest point on the Adriatic coast (Ankaran) to top of its highest peak (Triglav 2,864 metres) is just 88 kilometres (55 miles) as the crow flies. This enormous diversity in landscape, climate and topography is reflected in the country’s biodiversity and no more so than in the 179 species of butterflies regularly recorded within its 20,000 km². To put that in context Great Britain and Ireland (315,159 km², about 16 times as large) has 58 resident (or reintroduced) species. Some of the species in Slovenia are confined to the areas with a Mediterranean climate while others, some of them very rare such as False Ringlet and Purple-shot Copper are more typical of peatbogs and wetlands. Another environment rich in species, particularly in ringlets of the genus Erebia, are the high Alps above 1500 metres where more than a dozen species are found.
In geographical terms, the Primorska region in southwest Slovenia has the highest butterfly diversity in the country. Its limestone karstic ridges, dry grasslands, rich meadows and open woodlands represent an ideal mix of diverse habitats for butterflies. In some areas, species of different biogeographical zones (Mediterranean, Continental, Alpine) can be found all at the same site.
Butterflies of the Karst, Lake Cerknica and the Dinaric Alps
Climate and vegetation change very rapidly as one moves from the drier summer heat of the northern Adriatic inland across south-western towards the relative cool and humidity of Central and Eastern Europe in midsummer. The limestone of Karst country, the more acidic flysch soils derived from massive undersea mudslides and the peat-bogs where cold spring waters emerge increase the complexity of the habitat mix with peaks rising to almost 1800m above sea level on Mount Snežnik and over 1300m elsewhere in the Dinaric Alps across which vast forests of Beech and White Fir stretch out in the Balkans’ largest wilderness area stretching across Croatia and on into Bosnia and Herzegovina.
Our base at Lake Cerknica, is an Important Bird Area, a Site of Community Interest, Special Protection Area and Regional Park that covers more than 3,000 hectares, the lake itself being a vast turlough or temporary lake, rising and falling with the input of groundwaters from the surrounding limestone and the outputs into the subterranean river system that eventually finishes in the Black Sea. Butterfly diversity is extremely high in the wide range of habitats from wet to dry, from hot to cool and from high altitude to sea-level. The butterfly fauna of Slovenia is well-known, with an excellent national butterfly atlas, fine natural history museums and large and well-maintained collections of Lepidoptera stretching back to the 18th century when the country, as the Duchy of Carniola in the Austro-Hungarian Empire, was the stamping ground for natural history giants of the age such as Giovanni Scopoli who described the autumn-flying Woodland Grayling Hipparchia fagi from butterflies he collected in Carniola.
Many square kilometres of the lake bed consist of wet meadows cut once a year for hay and used by breeding corn, spotted and little crakes while black and white storks, the local pair of white-tailed eagles and large numbers of herons, bitterns and egrets use the flooded areas for feeding on the large stocks of fish and amphibians. On calm nights in summer the noise of the various crakes mixes with the booming of bitterns and the reeling of Savi’s warblers. The wet meadows throughout the area play host to a large number of rare butterflies though not all of these will be on the wing when we are there. Species in these habitats in mid-June include Large Chequered Skipper Heteropterus Morpheus, Large Copper Lycaena dispar (although the autumn brood is much larger), Sooty Copper L tityrus, Purple-shot Copper L. alciphron and Alcon Blue Phenargis alcon.
Peat-bogs such as those at Bloška Planota is one of the largest and most intact in Slovenia, is a rare habitat this far south and with a fantastic range of plants, butterflies and dragonflies. In woodland areas at this site Poplar Admiral Limenitis populi is seen in some years but Lesser Purple Emperor Apatura ilia is quite common. The upland grasslands surrounding the lake and the Dinaric Alps themselves are another rich habitat for butterflies. On the highest ground are small colonies of Clouded ApolloParnassius mnemosyne while the last Southern Festoons Zerynthia polyxena are still on the wing in mid-June. In the rockier area are rare species such as Chequered Blue Scolitantides orion, Northern Brown Argus Aricia artaxerxes and the very rare Geranium Argus Aricia eumedon. Dark-green Fritillaries Argynnis aglaja are often very common in mid-June together with Queen of Spain Fritillary Issoria lathonia in some years.
With much of the country’s land in the hands of the Church and a landed aristocracy until 1945, forests have survived across vast swathes of Slovenia and now cover 55% of the country, especially in upland areas. Though the areas of true ‘virgin’ forest are now small and scattered, Notrajnska Regional Park, covering 22,200 hectares, includes areas of old forest with many species of birds, animals and plants associated with them. The woodlands hold some interesting species including both White admiral L. camilla and the Southern white admiral L. reducta in warmer areas closer to the coast while Hungarian glider Neptis rivularis is sometimes seen along the forest tracks in mid-June. The area above the Cerknica Lake is a site for Scarce fritillary Euphydryas maturna.
We will also visit the dry hay meadows of the Karst, lower down and closer to the coast. Here the grassland fritillaries come to the fore with Glanville Melitaea cinxia, Heath M. athalia, Spotted M. didyma, Assman’s M. britomartis and Nickerl’s Fritillary M. aurelia all on the wing in mid-June although in varying numbers as well as large numbers of common species of blues, skippers and heaths. We will also look for two rare species at sites where they occur; Europe’s most endangered butterfly, the False Ringlet Coenonympha oedippus and the Chestnut Heath C. glycerion.
Other wildlife and plants…
Lake Cerknica is an important breeding site for many bird species including large numbers of whinchats and tree pipits. After dark is the best time to hear calling corncrakes and spotted crakes in the wetter parts of the lake as well as reeling Savi’s warblers and booming bitterns One of the last species to arrive at the lake in late May and early June is the scarlet rosefinch, at the limit of its distribution.
Short-toed and White-tailed eagle often hunt around the lake while the villages have Scops Owls, Black Restarts, Wrynecks and Red-backed shrikes. Fieldfares are common right around the lake and there are nine species of woodpecker within the park. Otters, Polecats and Beech Marten are all present close to our accommodation while the forests hold both Brown Bear and Grey Wolf. The latter prey on the Red and Roe deer which are common and easiest to see in the late evening and early morning.
The main botanical feature of the holiday will include the tail-end of the absolutely superb displays of spring flowers in the beech woodlands, including various hellebores, asarabacca, blue-eyed mary and haquetia, whilst the summer displays of grassland orchids such as Adriatic lizard, green-winged, burnt-tip and bog orchid will be underway in the splendid hay meadows in the Karst.
This promises to be a very popular tour – we recommend booking early to avoid disappointment!