Monday 13 June 2022

Dry karstic grasslands - cradle of biodiversity

The Karst's dry limestone grasslands, belonging to the order of Eastern sub-mediterranean dry grasslands (Scorzoneretaila villosae) represent one of the richest habitats in terms of biodiversity, not only in Slovenia, but also widely in Europe. At the same time they are among the most threatened habitats due to the abandonment of their traditional uses (grazing, hay-making) and the subsequent habitat loss by overgrowing. As such, they are highly-prioritized within the Natura 2000 network and a lot of efforts go into their preservation.

In Slovenia this type of grassland can be found predominantly in the western part of the country, in areas with sub-mediterranean climate on limestone: on the Karst plateau ("Classical Karst") and also in higher-elevated areas on the south-western edges of the Dinaric mountains (so-called High Karst).

We're very fortunate to live right here in the Karst and be able to spend a lot of time enjoying the variety of the dry grasslands, directly on our doorstep. In spring, the season of breeding bird censuses, we also dedicate a considerable amount of time to various bird monitorings in this particular habitat. Some of the rarest breeding birds in Slovenia such as Ortolan Bunting Emberiza hortulana, Tawny Pipit Anthus campestris and Rock Partridge Alectoris graeca depend almost entirely on dry limestone grasslands, while this habitat also supports important population densities of many other bird species. Although earlier in spring we have been mostly blogging about forests, from late April onwards our focus shifted to the Karst's open habitats. Therefore in this post we will try to present some of the most typical wildlife of karstic grasslands that we've been experiencing throughout the later part of spring.

Birding the dry karstic grasslands near Divača in early May.

In late April and the beginning of May we witnessed the welcome return of some later migrants such as Red-backed Shrikes Lanius collurio and Barred Warblers Sylvia nisoria. The former is a widespread bird of open areas across Slovenia, with the Karst holding some of the highest densities of the species in Slovenia. During a recent census (in early June) we counted an impressive 83 Red-backed Shrikes within a 230 hectares (2,3 km²) large area of pastures and hay-meadows. In some cooler areas of the Karst with an abundance of thorny bushes, the shrikes share the same microhabitat (bushes) with Barred Warblers. These interesting sylvids are quite common in bushy areas bordering wet meadows in the Notranjska region, but are quite rare in the Karst itself. Therefore we are always pleased when we find and count our local pairs near Divača, which probably represent the westernmost population of the species in the country. Among flowers the main spectacle in late April and early May was certainly stolen by carpets of Green-winged Orchids Anacamptis morio, Poet's Narcissi Narcissus poeticus radiiflorus and Three-toothed Orchids Neotinea tridentata, while rarer species included Fly Orchid Ophrys insectifera and the very-localised "Tuberous Valerian" Valeriana tuberosa, a plant of dry karstic grasslands.

Karstic pasture with donkeys, early May.
Barred Warbler Sylvia nisoria, early May.
Woodlark Lullula arborea, late April.
Red-backed Shrike Lanius collurio - female in early May.
Cuckoo Cuculus canorus, early May.
Wheatear Oenanthe oenanthe, male on migration, early May.
Green-winged Orchid Anacamptis morio & Poet's Narcissus Narcissus poeticus, early May.
Fly Orchid Ophrys insectifera, early May.
Lady Orchid Orchis purpurea, early May.
Military Orchid Orchis militaris, early May.
Military x Lady Orchid Orchis militaris x O. purpurea, early May.
"Tuberous Valerian" Valeriana tuberosa, very rare species of dry grasslands, early May.
Matted Globularia Globularia cordifolia, early May.
In early May we caught up with a butterfly that is on the wings much earlier in the year, but one we failed to see in April - the Southern Festoon Zerynthia polyxena. It is an endangered species of dry meadows, whose larvae feed on various species of birthwort Aristolochia spp. In the Karst it's a relatively common butterfly that can be admired on meadows, scrubland and woodland edges, usually singly or in small numbers. Early May is also the season of the first fritillaries - Glanville Melitaea cinxia and Knapweed Fritillaries Melitaea phoebe were the most numerous at first, but then Marsh Fritillaries Euphydryas aurinia also joined in.
Southern Festoon Zerynthia polyxena, early May.
Glanville Fritillary Melitaea cinxia, late April.
Knapweed Fritillary Melitaea phoebe, early May.
From mid May onwards we found ourselves more often on the dry grasslands along the Karst edge (Kraški rob) in the southwesternmost part of Slovenia. These grasslands host the last remaining Ortolan Buntings Emberiza hortulana in Slovenia and several censuses were targeted at this particular species that is sadly on the brink of extinction. Their population is very small and every year sees the return of less and less Ortolans. This season has proved to be the worst so far, as we managed to confirm only two breeding pairs in their stronghold area (and overall in Slovenia). For comparison, last year 6 pairs were found in the same area (and 8 in total in Slovenia). Back in 2015-2017 we documented and analised the decline of the Ortolan in Slovenia and studied the same population that now hosts the last remaining pairs. For more info, including the possible reasons for the species' decline see our paper.
Dry karstic grasslands along the Karst edge, SW Slovenia.
Ortolan Bunting Emberiza hortulana - the only two males in Slovenia, mid May.
Ortolan Bunting Emberiza hortulana - female, early June.
Ortolan Bunting's habitat with Wild Sage Salvia officinalis.
Grasslands in Slovenia where Ortolan went extinct and Mt. Učka (Croatia) in the distance, where the species is still doing well.
Abandonment of traditional land use on the Karst edge and overgrowing of agricultural landscape.
The abandonment of grazing and hay-cutting is the major problem of species' decline on dry grasslands (be it birds, invertebrates or plants). Most of the Karst was once grazed extensively by sheep, but nowadays few areas have maintained this type of use. However there are still some larger patches of grasslands along the Karst edge, where biodiversity is incredibly rich compared to other areas. Spring bird censuses are a real joy in this type of habitat. The air is filled with the songs of Skylarks Alauda arvensis, Woodlarks Lullula arborea, Corn Buntings Emberiza calandra, Hoopoes Upupa epops, Cuckoos Cuculus canorus, Wrynecks Jynx torquilla, Common Whitethroats Sylvia communis, while almost every bush seems to hold a pair of Red-backed Shrike Lanius collurio. In smaller densities there's also Stonechat Saxicola torquatus, Linnet Linaria cannabina, Quail Coturnix coturnix, Nightingale Luscinia megarhynchos, Cirl Bunting Emberiza cirlus and Yellowhammer Emberiza citrinella, while rare birds on a national scale include Tawny Pipit Anthus campestris and Short-toed Eagle Circaetus gallicus. Later in the season (second half of May) Golden Oriole Oriolus oriolus and Turtle Dove Streptopelia turtur also add to the dawn chorus. Among raptors an interesting species is the Honey Buzzard Pernis apivorus that can be regularly observed "hunting" on the ground or sitting on small bushes. Where grasslands give way to the limestone cliffs and screes of the Karst edge, Blue Rock Thrush Monticola solitarius, Rock Bunting Emberiza cia and Alpine Swift Apus melba become particularly common.
Species-rich dry grasslands along the Karst edge (Kraški rob), SW Slovenia.
Skylark Alauda arvensis in early May (top) & early June (bottom).
Woodlark Lullula arborea (juvenile), mid May.
Red-backed Shrike Lanius collurio (male), mid May.
Red-backed Shrike Lanius collurio with a juicy spider.
Red-backed Shrike Lanius collurio (female), mid May.
Hoopoe Upupa epops, early June.
Corn Bunting Emberiza calandra, mid May.
Short-toed Eagle Circaetus gallicus, mid May.
Tawny Pipit Anthus campestris, mid May.
Stonechat Saxicola torquatus (male), mid May.
Linnet Linaria cannabina on barbed wire at the Slovenia-Croatia border, mid May.
Cirl Bunting Emberiza cirlus (male), early June.
Turtle Dove Streptopelia turtur, early June.
Yellowhammer Emberiza citrinella (male), early June.
Barred Warbler Sylvia nisoria (male), early June.
Mistle Thrush Turdus viscivorus, mid May.
Wheatear Oenanthe oenanthe, possible breeding female in early June.
Honey Buzzard Pernis apivorus (male), early June.
Nightingale Luscinia megarhynchos, late May.
Wryneck Jynx torquilla, early June.
Icterine Warbler Hippolais icterina on migration, late May.
Blue Rock Thrush Monticola solitarius, early June.
One morning when we were finishing a bird census in the dry grasslands near Rakitovec, we also had a close encounter with two Golden Jackals Canis aureus. This increasingly common species in Slovenia is more often heard howling than seen. However in the last years we already had some multiple encounters with this strange canid. In most occasions the animals behave in a rathe naive manner, unlike a fox or other wild animal. They always seem to notice the presence of people when it's too late and they have already been photographed multiple times...
Golden Jackal Canis aureus, early June.
Red Deer Cervus elaphus at dawn during a census in early June.
From the botanical point of view, the richest dry grasslands are those belonging to the association of Dwarf Sedge Carex humilis and Rock Knapweed Centaurea rupestris known as Carici humilis-Centaureetum rupestris (for the phytocenologists among you). They include a wide variety of plant species, many of which are either very rare or localised in Slovenia. These plants belong either to the Mediterranean/Balkan or to the Steppic element of the flora. The dry grasslands usually come alive later in the season, from early May to June. During this time there's an exchanging palette of different blooms that usually terminates in early summer, when the grass becomes "burned" by the strong sunshine and drought.
Carici humilis-Centaureetum rupestris with Scorzonera villosa in late May.
Jurinea mollis, late May.
Feather Grass Stipa eriocaulis & Dittany Dictamnus albus, late May.
Dittany Dictamnus albus, late May.
"Javorka's Golden Drop" Onosma (echioides) javorkae, late May.
Silvery Broom Genista sericea, late May.
Genista sylvestris, late May.
Wild Sage Salvia officinalis, late May.
"Strawberry Spurge" Euphorbia fragifera, late May.
Cantabrican Morning Glory Convolvulus cantabrica, early June.
Illyrian Iris Iris pallida ssp. illyrica, mid May.
Grass-leaved Iris Iris graminea, mid May.
Smoke Bush Cotinus coggygria on dry limestone wall, mid May.
Smoke Bush Cotinus coggygria in flower, mid May.
Smoke Bush Cotinus coggygria in seed, early June.
Sand Leek Allium scorodoprasum, early June.
Species-rich hay meadows in the Karst, early June.
Counting birds in the dry grasslands.

Because the karstic landscape is very rocky and dry stone walls have been traditionally built to divide old pastures, dry grasslands also support an interesting herpetofauna. The commonest species is probably European Green Lizard Lacerta viridis, but Wall Lizard Podarcis muralis and Dalmatian Wall Lizard Podarcis melisellensis are also common. Among snakes, the most typical representative of this habitat is certainly the Nose-horned Viper Vipera ammodytes
From early June onwards, the grasslands also come alive with butterflies. The first species to emerge en masse are Black-veined Whites Aporia crataegi and Pearly Heaths Coenonympha arcania, followed by Marbled Whites Melanargia galathea and a whole variety of Fritillaries Melitaea spp. From mid June onwards, it's already the time of the "summer species" such as Woodland Grayling Hipparchia fagi, Great Banded Grayling Brintesia circe and the rare Great Sooty Satyr Satyrus ferula (in Slovenia found only on dry limestone grasslands). June is also the month of burnets. Several species can be encountered together on dry grasslands, including the common Six-spot Burnet Zygaena filipendulae, the Transparent Burnet Zygaena purpuralis and the distinctive Carniolan Burnet Zygaena carniolica (named after Slovenia's historic region of Carniola). Nine-spotted Moth Amata phegea is also a very common species at this time of year.
Dalmatian Wall Lizard Podarcis melisellensis, early June.
European Green Lizard Lacerta viridis, early June.
Pearly Heath Coenonympha arcania, late May.
Glanville Fritillary Melitaea cinxia, late May.
Marsh Fritillary Euphydryas aurinia, late May.
Knapweed Fritillary Melitaea phoebe, late May.
Spotted Fritillary Melitaea didyma (caterpillar), late May.
Spotted Fritillary Melitaea didyma, early June.
Nickerl's Fritillary Melitaea aurelia, early June.
Black-veined White Aporia crataegi, late May.

Great Sooty Satyr Satyrus ferula, early June.
Six-spot Burnet Zygaena filipendulae, early June.
Twin-spot Fritillary Brenthis hecate, early June.
Carniolan Burnet Zygaena carniolica, early June.
Burnet mix: Zygaena purpuralis, Z. filipendulae & Amata phegea
Carniolan feast, early June.
Nine-spotted Moth Amata (Syntomis) phegea, early June.
Marbled White Melanargia galathea (below the form leucomelas), early June.
Meadow Brown Maniola jurtina, early June.
 Pedestredorcadion arenarium (Cerambycidae), early June.
Orchids are among the species of plants that in late May and early June steal the show. Although we are not particularly huge fans of orchids (there are so many other interesting plants out there!), it's still very nice when you find yourself on a small meadow packed with orchids of all sorts. Also in this respect, the Karst edge, on the border of the Istrian peninsula, hosts some of the greatest orchid diversity in Slovenia. Apart from several species of Ophrys that give their best at this time of year, the most prominent in this season are usually Pyramidal Orchids Anacamptis pyramidalis and Adriatic Lizard Orchids Himantoglossum adriaticum. The latter is a particularly interesting one, as in the last ten years or so it has undergone a large range expansion. Once only confined to Istria and parts of eastern Slovenia, the Adriatic Lizard Orchid seems to be taking a hold in the Karst plateau itself and even in other areas of continental Slovenia. This year we have observed it in various spots in the Karst around Sežana, Divača and Dutovlje, as well as in the Reka valley. Probably most of these sites are new localities for the species in Slovenia.
 Late Spider Orchid Ophrys holosericea, late May.
Bee Orchid Ophrys apifera, late May.
Ophrys sulcata, late May. A rare species in Slovenia only found at the Karst edge & Istria.
Burnt-tip Orchid Neotinea ustulata, late May.
Pyramidal Orchid Anacamptis pyramidalis, late May.
Adriatic Lizard Orchid Himantoglossum adriaticum, late May.
And now to the meadows of the so-called "High Karst". As many of our readers will already know, in late May or early June it is also in our tradition to visit mount Nanos (1242 m), the natural border between the Primorska and Notranjska regions. The most interesting habitat on Nanos are its mountain grasslands and meadows, as well as rocky slopes and limestone screes. The meadows are similar in composition to the ones in the "Classical Karst" but have an addition of several Alpine and Balkan elements. 
From the ornithological point of view Nanos has been a reliable site where we used to see Rock Thrush Monticola saxatilis and several other "rocky" species. Sadly in recent years we have witnessed the decline (and perhaps even the disappearence) of this colourful thrush. The rocky grasslands near the top of Pleša (Nanos' summit) were the territory of at least 3-4 Rock Thrushes, as well as the odd Blue Rock Thrush Monticola solitarius. This year, at the end of May we searched hard for Rock Thrush, but unsuccessfully. Instead we found a traditional territory "usurped" by a pair of Blue Rock Thrushes, at an altitude of around 1100 m a.s.l. This Mediterranean species might be benefitting from global warming and pushing its alpine cousin higher up the mountains. On the other hand Rock Thrush seems to be more dependant on active grazing than Blue Rock Thrush and it might be disappearing also because of the abandonment of traditional land use, a bit like the Rock Partridge Alectoris graeca (an extinct species on Nanos).
Rock Thrush habitat on mount Nanos.
Blue Rock Thrush Monticola solitarius (male), late May.
Blue Rock Thrush Monticola solitarius (female), late May.
Rock Thrush Monticola saxatilis in the same area in May 2017.
The karstic ridges of mount Nanos and Trnovski gozd above the Vipava valley hold Slovenia's largest population densities of Rock Buntings Emberiza cia. Sharing the same rocky habitat are also Crag Martin Ptyonoprogne rupestris, Peregrine Falco peregrinus and the Golden Eagle Aquila chrysaetos, while cliff faces lower down in the valley hold breeding Eagle Owls Bubo bubo. Most of the grasslands on the Nanos plateau are not extensively grazed anymore (since a few decades) and the birdlife is now impoverishing. Birds that can be still found include Skylark Alauda arvensis, Woodlark Lullula arborea, Red-backed Shrike Lanius collurio, Quail Coturnix coturnix and Stonechat Saxicola torquatus, but in much lower densities than in the grasslands of the "Classical Karst".
Rock Bunting Emberiza cia, late May.
Alpine Chamois Rupicapra rupicapra, late May.
The spectacular mountain meaodws on mount Nanos.
Skylark Alauda arvensis, late May.
If the birdlife on Nanos' grasslands and meadows is not particularly rich, the same cannot be said for the plants and the butterflies. The most interesting floral elements of the "High Karst" include such prominent plants as White Asphodel Asphodelus albus, Carniolan Lily Lilium carniolicum, Kojnik's Iris Iris sibirica erirrhiza, False White Helleborine Veratrum album, Yellow Gentian Gentiana lutea, Jacquin's Vetch Anthyllis montana jacquinii, Carniolan Vetch Astragalus carniolicus and several others. 
Among butterflies, the most prominent species on the wings in late May and early June is the Marsh Fritillary Euphydryas aurinia, here reaching high population densities. An overall rare species in Slovenia but common on Nanos is the Geranium Argus Aricia eumedon, whose larval food plant in these meadows is Bloody Cranesbill Geranium sanguineum. Clouded Apollo Parnassius mnemosyne is another typical butterfly of the dry meadows at this altitude.
White Asphodel Asphodelus albus & Kojnik's Iris Iris sibirica erirrhiza, late May.
Kojnik's Iris Iris sibirica erirrhiza, late May.
Grass-leaved Iris Iris graminea, late May.
Carniolan Lily Lilium carniolicum, late May.
Orange Lily Lilium bulbiferum, late May.
Carniolan Vetch Astragalus carniolicus & Alpine Mezereon Daphne alpina, late May.
French Flax Linum narbonense, late May.
Marsh Fritillary Euphydryas aurinia on French Flax Linum narbonense, late May.
Marsh Fritillary Euphydryas aurinia on Grass-leaved Iris Iris graminea, late May.
Marsh Fritillary Euphydryas aurinia, late May.
Geranium Argus Aricia eumedon on Bloody Cranesbill Geranium sanguineum, late May.
Nickerl's/Assman's Fritillary Melitaea aurelia/britomartis, late May.
Woodland Ringlet Erebia medusa, late May.
Grizzled Skipper Pyrgus malvae, late May.
And for the end, if we return to the forest... Nanos also holds some of the best subalpine beech Fagus sylvatica stands, where Ramsons Allium ursinum puts on a real spectacle in late spring. At an altitude of 1100-1300 metres, Wild Garlic here blooms much later in the season than lower down in the valleys. The last days of May are usually the best to wintess white carpets of flowers in the forest, a sight we never get tired of, although we see it every year!
Ramsons or Wild Garlic Allium ursinum, late May.
Dawn in the dry grasslands, at the feet of Nanos.
More about dry karstic grasslands: