Saturday 23 July 2022

Summer in the forest

It's summer but keeping up with the blog seems even more difficult than in spring! Especially so now that we can tweet quickly and more often. Summer is not a particularly busy time of the year regarding our field activities, but somehow we've become a bit lazy for writing longer posts. When we last blogged it was mid June and we were just finishing with our last bird censuses in the Karst's dry grasslands. Soon after this "open habitat intermezzo" and a short trip to the Austrian Alps (a blog on this hopefully in the future), we moved back to our forests. Summer is a quiet time for birding, especially in forest habitats, where it is very difficult to spot woodpeckers, owls and other shy forest species in the thick green canopies. However, if one wants to explore and look for other types of wildlife, then summer is still an excellent time. 

This blog, focusing on summer wildlife in the forests begins in late June, when we went to check on the nesting progress of our local pair of Black Storks Ciconia nigra. Since last year, when we discovered the nest (a very old nest, probably active for a decade or more), we check it twice a year: once in early spring, to see if the pair has returned and once later in the season when the chicks are big. So far it is the only known nest of this rare species in western Slovenia and since forestry works expanding to the nesting area are always a possible threat, it's good to monitor the situation. When we checked last year there was only one chick in the nest, so this year we were very glad to find two chicks instead. At the time of writing both chicks should be already capable of flying and have probably left the nest, at least for some "flight tests".

Black Stork Ciconia nigra chicks, W Slovenia, June 2022.
Same nest as above, but with only one chick in June 2021.


In the first days of July it was already very hot, so we kept retreating to the shade of the oak-beech woodlands in the flysch hills at the edge of the Karst. Those were the last days of singing activity for many birds, before the advent of the "summer silence", when at the end of the breeding season, the forests fall silent. We were therefore surprised to hear a singing Cuckoo Cuculus canorus, probably the latest one we've ever heard. But even more surprising was hearing a sound we usually associate with spring migration: the trill of a singing Wood Warbler Phylloscopus sibilatrix. After some considerable effort trying to spot it in the canopies, we finally put our eyes on it. This common migrant through woodlands across Slovenia is a very rare breeder in the country, with few individuals stopping and holding territory later than mid May. Supporting cast in the forest were also a male Honey Buzzard Pernis apivorus landing on the ground to search for wasps' nests, Golden Oriole Oriolus oriolus and Middle Spotted Woodpecker Leiopicus medius. The latter we also heard and seen several other times in June, with most observations involving small parties of juveniles, roving around even in open areas with sparse oaks.

Wood Warbler Phylloscopus sibilatrix, flysch hills, early July.
Middle Spotted Woodpecker Leiopicus medius, Karst, mid June.

In contrast to the dry limestone Karst, the nearby flysch hills are rich with water. However even there the ongoing summer drought has dried out most of the small forest streams, leaving only the main streams still going. In a small pool we found several interesting animals all concentrated in one spot. Among them, the most notable were six White-clawed Crayfish Austropotamobius pallipes (an endangered species we haven't seen in many years), hiding among underwater roots. There were also lots of well-developed larvae of Fire Salamanders Salamandra salamandra and huge numbers of Common Toad Bufo bufo tadpoles, while Beautiful Demoiselles Calopteryx virgo were quartering the water edges. In an area we checked back in spring, we were glad to still find many Yellow-bellied Toads Bombina variegata (around 10) hiding in muddy puddles on a disused forest road.

A pool of water along a forest stream in the flysch hills in early July.
White-clawed Crayfish Austropotamobius pallipes, flysch hills, early July.
Fire Salamander Salamandra salamandra (larva), flysch hills, early July.
Common Toad Bufo bufo (tadpoles), flysch hills, early July.
Yellow-bellied Toad Bombina variegata, flysch hills, early July.
Beautiful Demoiselle Calopteryx virgo, flysch hills, early July.


In summer we like to look for beetles, especially longicorns (Cerambycidae), but this year the search has been initially quite slow. It wasn't until the first days of July that we found our first Beech Longhorn Beetles Morimus funereus of the year. This common, but very attractive flight-less species deposits its eggs mostly in oak and beech wood and as with other longicorns, the easiest way to find it, is to search carefully on recently-cut logs stacked at the side of forest roads. This year the flight of Stag Beetles Lucanus cervus has began quite early, already at the end of June, but their activity seemed more prolonged into the season. We were lucky to see this iconic beetle in our garden (due to all the oak woodland nearby) on a daily basis from late June to mid July. Males were most active in the initial stage, while later on we observed also several females. This season we've been paying more attention also to Jewel Beetles (Buprestidae) and came across a Red-listed and protected species in our neighbourhood - Dicerca berolinensis.

Beech Longhorn Beetle Morimus funereus, Karst, July.
Stag Beetle Lucanus cervus (male), Karst, July.
Stag Beetle Lucanus cervus (female), Karst, July.
Jewel Beetle Dicerca berolinensis (Buprestidae), Karst, June.
Southern White Admiral Limenitis reducta, Karst, July.

Remaining in our local area, one evening we went to enjoy a sunset in the dry meadows at the edge of the forest not far from our home. We were rewarded with small numbers of Red Deer Cervus elaphus and Roe Deer Capreolus capreolus grazing in the open, plus singing Nightjars Caprimulgus europaeus and Tawny Owls Strix aluco. It's not comparable to the wilderness of Snežnik, but still not bad for the local patch!

Evening wildlife watching in the Karst's extensive meadows in July.
Red Deer Cervus elaphus (stag), July.
Mt. Nanos towering above the forests on the edge of the Karst.


In early July we also took a trip to Trnovski gozd (Trnovo forest) and its southern edge. We visit this area every summer, when the diversity of Lepidoptera is at its highest, but this year our timing seemed even more accurate than usual. The roadside edges and meadows at the edge of the forest were full of blooming Yellow Melancholy Thistles Cirsium erisithales, as well as other Cirsium spp. and various large umbellifers (Apiaceae). These were in turn attracting an incredible variety of pollinators, all feasting simultaneously on the flowers. Looking at the incredible numbers of Marbled Whites Melanargia galathea, Ringlets Erebia spp., Fritillaries, longhorn beetles & wild bees of all sorts, we realised we've never experienced such an abundance and variety of pollinators at one time! We recorded a short video that wasn't actually very elaborate and was made in a fuss, but apparently was highly appreciated on Twitter: it got almost 90K views and +2100 likes! Speaking about species, the most abundant butterflies were Marbled White, Silver-washed Fritillary Argynnis paphia, Dark Green Fritillary Argynnis aglaja, Arran Brown Erebia ligea, Styrian Ringlet Erebia stirius, Great Sooty Satyr Satyrus ferula, Queen of Spain Issoria lathonia, while moths included many Hummingbird Hawk-moths Macroglossum stellatarum & Burnets Zygaena spp. & Amata phegea. This year, apart from tens of different species of bumblebee, Violet Carpenter Bees Xylocopa violacea seemed to be more numerous than in other years. Among longhorn beetles, one of the commonest species visible on flowers (especially umbellifers) in July is the Spotted Longhorn Rutpela maculata, although we also found several other species including the amazing Wasp Beetle Clytus arietis. However the highlights were two large species of mountain butterflies: Apollo Parnassius apollo on the dry limestone slopes at the edge of the forest and Purple Emperor Apatura iris sucking minerals from a forest road and on the leaves of a huge flowering lime Tilia spp.

Butterflies & other pollinators in Trnovski gozd, early July.

Apollo Parnassius apollo, Trnovski gozd, early July.
Styrian Ringlet Erebia stirius, Great Sooty Satyr Satyrus ferula & Arran Brown Erebia ligea.
Styrian Ringlet Erebia stirius, Trnovski gozd, early July.
Violet Carpenter Bees Xylocopa violacea, Trnovski gozd, early July.
"Checkered Bee Beetle" Trichodes apiarius, Bee Beetle Trichius fasciatus, Spotted Longhorn Rutpela maculata, Trnovski gozd, early July.
An umbellifer full of beetles of all sorts. Trnovski gozd, early July.
 Anastrangalia sanguinolenta (longhorn beetle, Cerambycidae), Trnovski gozd, early July.
Wasp Beetle Clytus arietis (longhorn beetle, Cerambycidae), Trnovski gozd, early July.
Flatheaded Woodborer Buprestis novemmaculata (Buprestidae), Trnovski gozd, early July.
Purple Emperor Apatura iris (note blue shine on right wing), Trnovski gozd, early July.
Purple Emperor Apatura iris high in the canopy of a lime Tilia spp.


Next on plan, in the first week of July was a 3-day trip with a group of naturalists to the Dinaric forests of Kočevje in southern Slovenia. Our primary target was to visit the old-growth forests of the region, which contain some remnants of primeval forest. As the group was quite varied in terms of interests, we explored the area in a relaxed and holiday-like mood. Our base was a small forest hut on a clearing, with no electricity, no water and no phone signal. The only source of water (used for washing) was from a well. A perfect little piece of heaven in the forest!

Our little house in the mighty forests of Kočevski rog.
Old-growth forest reserves in the Kočevsko region, July.

On the ornithological front we didn't expect to see much, given the high summer temperatures and reduced activity of birds. However we were pleasantly surprised when walking on one of the trails along an old-growth reserve. In the early evening the usual "fuss" made by Blackbirds Turdus merula and Song Thrushes Turdus philomelos alerted us to the presence of a Ural Owl Strix uralensis nearby. At first we didn't see the bird as it was still hidden in thick cover, but a few minutes later someone glimpsed a dark bird approaching. It landed on a tree some 60 metres away from us and then we could finally see it: a completely melanistic Ural Owl! The bird allowed great views and everyone in the group managed to see it, despite the dimming evening light. Dark-morph Ural Owls such as this represent 5-15% of the Slovenian Ural Owl population and seem to be somehow easier to find in the Kočevska region (check this paper for more).

Melanistic Ural Owl Strix uralensis (last pic by Davide Scridel).

In the forests of Kočevsko we also regularly came across other forest birds like Bullfinch Pyrrhula pyrrhula, Crossbill Loxia curvirostra, Willow Tit Poecile montanus, Crested Tit Lophophanes cristatus, Eurasian Treecreeper Certhia familiaris, Grey-headed Picus canus & Black Woodpecker Dryocopus martius, Goldcrest Regulus regulus and many others. Especially interesting was the presence of several Middle Spotted Woodpeckers Leiopicus medius that we were usually seeing in the abandoned forest clearings and around villages. In the same habitat, where some meadows with fruit trees were still active, families of Red-backed Shrikes Lanius collurio were present. One day we also saw two Stock Doves Columba oenas, a rare, forest-breeding bird in this region. At night Tawny Owls Strix aluco as well as Edible Dormice Glis glis made us company in the immediate vicinity of our hut.

Among mammals the most interesting species were a Red Deer Cervus elaphus stag on a forest glade in the evening and a group of Alpine Chamois Rupicapra rupicapra on the limestone cliffs towering above the Kolpa river. In the latter site we also had brief glimpses of Horvath's Rock Lizard Iberolacerta horvathi, an endemic lizard of the Julian Alps & the Balkans.

Alpine Chamois Rupicapra rupicapra, Kočevsko, July.
Limestone cliffs with native Black Pine Pinus nigra stands above the Kolpa valley, July.
View down to the Kolpa river on the border with Croatia.

It terms of invertebrates we were really busy. Common butterflies in forest clearings or along forest roads included Ringlet Aphantopus hyperantus (scarce in most of western Slovenia where we usually roam), Marbled White Melanargia galathea, Great Banded Grayling Brintesia circe, White Admiral Limenitis camilla and the occasional Purple Emperor Apatura iris, while Scarlet Tiger Moth Callimorpha dominula was also very common. But the best attraction for us were longhorn beetles. One sunny day while we were walking a path along an old-growth forest of beech Fagus sylvatica, we were extremely delighted to find two Alpine Longhorn Beetles Rosalia alpina. This endangered and rare species deposits its eggs in dead beech wood and its life cycle as a wood-boring larva lasts for 2-3 years. Another interesting longicorn that we found right on the doorstep of our forest hut was the Tanner Beetle Prionus coriarius, a polyphagous species predominantly on beech and oak Quercus spp. Some other commoner species of longhorn beetles, as well as various other invertebrates, including several Owlflies Libelloides macaronius were also found in the occasional hay meadows in the middle of the forest.

Alpine Longhorn Beetles Rosalia alpina, Kočevsko, July.
Tanner Beetle Prionus coriarius, Kočevsko, July.
Purple Emperor Apatura iris, Kočevsko, July.
Woodland Brown Lopinga achine, Kočevsko, July.
Black Arches Lymantria monacha, Kočevsko, July.
Scarlet Tiger Moth Callimorpha dominula
Alpine Newt Ichthyosaura alpestris leaving a pond after breeding, Kočevsko, July.
Roman Snail Helix pomatia, Kočevsko, July.
Yellow-collared Flatback Millipede Polydesmus collaris, Kočevsko, July.

Looking for inverts on an old hay meadow in the middle of the forest.
Great Yellow Gentian Gentiana lutea, Kočevsko, July.
Leptura aethiops (Cerambycidae), Kočevsko, July.
Anthaxia nitidula (Buprestidae), Kočevsko, July.
Owlfly Libelloides macaronius, Kočevsko, July. Photo by Davide Scridel.
Ringlet Aphantopus hyperantus, Kočevsko, July.
Ringlet Aphantopus hyperantus & Silver-washed Fritillary Argynnis paphia, Kočevsko, July.
Marbled Fritillary Brenthis daphne, Kočevsko, July.
Evening on a forest clearing, Kočevsko, July.


Despite the increasing heat and difficult conditions for birding, in mid July we were around the temporary lake of Cerknica (Cerkniško jezero) several times, showing the area to some visitors from abroad. Because the lake is completely dry at this time of year and there are very few birds to be found (highlight was only a Short-toed Eagle Circaetus gallicus), we strayed into the cool forests of Javorniki and Snežnik. There we looked for Ural Owl and other typical forest birds. On one occasion our mission to find the owl failed, but instead in the Javorniki hills above lake Cerknica we found yet another Alpine Longhorn Beetle Rosalia alpina on some logs stacked by the side of the road. We were once again extremely happy for the find, because the species is considered almost totally absent from the Javorniki-Snežnik forest complex, while there are some records for the area around the lake. Sadly, beetles found on cut logs, deposit their eggs into the timber, which is later removed from the forest and burned, therefore the brood is destroyed. Because of this it is advisable to remove the cut timber from the forest soon after felling. Our Rosalia was found on a log that has been cut and left there last year.

Alpine Longhorn Beetle Rosalia alpina, Javorniki Mts., mid July.

White Admiral Limenitis camilla sucking minerals on the corpse of a Purple Emperor Apatura iris!
White Admiral Limenitis camilla, Javorniki Mts., mid July.
 Copper Underwings Amphipyra pyramidea/berbera roosting in a Black Woodpecker's feeding cavity, Javorniki Mts., mid July.
Woodland Grayling Hipparchia fagi, Javorniki Mts., mid July.


At last, after some considerable effort, one evening we also managed to find a Ural Owl Strix uralensis in the Javorniki mountains. It was a tail-less male that was moulting its tail feathers and looked quite strange, especially in flight. We watched it and enjoyed it thoroughfully with the scope for something like half an hour. Given the low availability of rodents this year (after 2021's rodent explosion) very few (if any at all) Ural Owls bred. Therefore animals were not so vocal and territorial, so finding occupied territories was a bit harder than usual. Autumn will probably bring some more territoriality (and the leaves will fall), so finding this iconic forest bird will be perhaps a bit easier in the coming months.

Ural Owl Strix uralensis, Javorniki Mts., mid July.
Ural Owl catching the last rays of sun.
Tail-less Ural Owl through the telescope - phone-scoped by Matteo Skodler.


Wandering around the forests of Snežnik-Javorniki, looking for birds, one has always the possibility (although remote) to spot a Brown Bear Ursus arctos, or at least its signs. Lately we've been quite good in finding its footprints, but especially its droppings along forest roads - they are actually hard to miss! However our luck escalated when one evening while driving close to a forest clearing, we spotted a young male Brown Bear running away from us. Staying in the car and driving on slowly along the road, we could watch him walking steadily through the forest a few tens of metres away from the road. The encounter lasted for several minutes, before the bear disappeared into a thick stand of conifers. It was the perfect rounding up of a difficult afternoon birding, when we showed the hard-earned Ural Owl to our Dutch friends (you can imagine their excitement!).

Footprint of Brown Bear Ursus arctos by Matteo Skodler.
Corn-flavoured droppings of Brown Bear on a forest road, by Matteo Skodler.
Brown Bear Ursus arctos from the car, Javorniki Mts., mid July.
Short video of the Brown Bear walking through the forest at twilight.

Evening wildlife watching on the meadows at the edge of the forest, Javorniki Mts., mid July.


Last but not least in mid July we also took a traditional summer hike to the top of mount Snežnik (1796 m), the highest non-alpine peak in Slovenia. Most of the lower part of the walk goes through montane beech-silver fir forest (Abieti-Fagetum), so there we found the typical summer flowers of the season, including the impressive Heart-leaved Oxeye Telekia speciosa, while the only remaining orchids were the quite numerous Dark-red Helleborines Epipactis atrorubens. Like in Trnovski gozd, also here the roadside edges were full of blooming Yellow Melancholy Thistle, which attracted a large number of butterflies. Most were Silver-washed Fritillaries Argynnis paphia, including several dark individuals of the form valesina, with their beautiful dark-blue glossy shine on the wings. Also common were Peacock Aglais io, Small Tortoiseshell Aglais urticae, Arran Brown Erebia ligea and Comma Polygonia c-album. Also here there were large numbers of Violet Carpenter Bees Xylocopa violacea, mostly favouring the flowers of Rosebay Willowherb Chamerion angustifolium. This time the umbellifers were completely taken over by wasps (probably Vespula vulgaris/germanica) and the occasional longhorn beetle. Once again a great abundance of pollinators (or stealers of pollen) and a great spectacle to watch!

Heart-leaved Oxeye Telekia speciosa, Mt. Snežnik, mid July.
Dark-red Helleborine Epipactis atrorubens, Mt. Snežnik, mid July.
Silver Fir Abies alba with new cones, Mt. Snežnik, mid July.
Alpine Buckthorn Rhamnus fallax, Mt. Snežnik, mid July.
Arran Brown Erebia ligea, Mt. Snežnik, mid July.
Silver-washed Fritillary Argynnis paphia f. valesina, Mt. Snežnik, mid July.
Peacock Aglais io, Mt. Snežnik, mid July.
Wasps Vespula vulgaris/germanica on Laserwort Laserpitium siler, Mt. Snežnik, mid July.
Two-banded Longhorn Beetle Rhagium bifasciatum, Mt. Snežnik, mid July.
Higher up above the treeline beech gives was to thick stands of Mountain Pine Pinus mugo, followed (and sometimes intermixed) with rocky subalpine meadows. This is the perfect habitat for Adders Vipera berus. Mount Snežnik is a reliable site to observe the melanistic (basically black) morph, where this colour variant seems to be quite common. Walking up the narrow path through the mugo pines we soon found a black adder basking in the sun among some creeping pine branches. Given the size it was probably a female and was apparently well-used to hikers walking a few decimetres away from it. We could watch it and photograph it for a long time.
The stand of Mountain Pine Pinus mugo around the summit of Mt. Snežnik.
Melanistic Adder Vipera berus, Mt. Snežnik, mid July.
The thick stands of Mountain Pine are also the habitat of several breeding birds such as Crossbill Loxia curvirostra, Dunnock Prunella modularis and Chiffchaff Phylloscopus collybita, while Bullfinches Pyrrhula pyrrhula and Siskins Spinus spinus also frequently visit this habitat to feed.
Among plants here it's already possible to find the first Edelweiss Lentopodium alpinum and several other interesting species of plants, although most species put on the best show in the subalpine meadows on the very top of the mountain. Mid July is usually the peak time of blooming for the mountain flora on Snežnik. However this year we were a bit disappointed to find the meadows very dry and already mostly "over-flowered". Edelweiss and some Fairy's Thimbles Campanula cochleariifolia were in good shape, but the characteristic Edraianthus Edraianthus graminifolius was already gone over. At the same time the first "Little Gentians" Gentianella spp. and Grass-of-Parnassus Parnassia palustris, two typical plants of late summer and early autumn, were already blooming in good numbers.
Crossbill Loxia curvirostra (male above, female below), Mt. Snežnik, mid July.
Mountain Pine Pinus mugo with cone, Mt. Snežnik, mid July.
Northern slopes of Snežnik with a carpet of Pinus mugo. Loška dolina (valley) visible in the distance.
Campion-leaved Scabious Scabiosa silenifolia (endemic to the Dinaric mountains & Apennines), Mt. Snežnik, mid July.
Small Tortoiseshell Aglais urticae, Mt. Snežnik, mid July.
Violet Carpenter Bee Xylocopa violacea, Mt. Snežnik, mid July.
Queen of Spain Issoria lathonia, Mt. Snežnik, mid July.
Edelweiss Leontopodium alpinum, Mt. Snežnik, mid July.
Edraianthus Edraianthus graminifolius, Mt. Snežnik, mid July.
Little Gentian Gentianella spp., Mt. Snežnik, mid July.
Carniolan Honewort Trinia glauca carniolica, Mt. Snežnik, mid July.
Maly's Moon Carrot Seseli malyi, Mt. Snežnik, mid July.
View from Snežnik towards Croatia - forests as far as the eye can see!
From the top of Snežnik towards Kočevsko, with the cliffs of Kolpa (featured above).