Tuesday, 15 August 2023

Birds & other wildlife in burned forests of the Karst

The Karst region stretching bewteen southwestern Slovenia and northeastern Italy, on the edge of the Mediterranean, has long been characterised by summer wildfires. Due to its limestone terrain with virtually no surface water, the region is prone to prolonged summer droughts and therefore to forest fires. The extensive fire from July 2022 will be remembered as the largest wildfire in Slovenia's history (more details on this event here). The fire affected a total of 4500 hectares, stretching in the transboundary area between Slovenia and Italy. In Slovenia it burned an area of 3707 hectares, of which 2902 hecteres were forests. However most of the burned forest was composed of non-native stands of black pine Pinus nigra (planted extensively throughout the Karst in the 19th century) and areas of native thermophilous scrub of relatively low biodiversity importance (bushes, young trees). Therefore the damage done to the ecosystem is relatively low, compared to the economical damage on the value of timber. Fortunately firefighters also managed to keep the flames away from the numerous villages scattered within the wildfire area.

In spring 2023 we set a research group among colleagues and friends, to monitor birds in the burned trans-boundary area. The first breeding season of censuses is over and hopefully we'll be able to monitor the situation on the study plot also in the next couple of years. Results from this year's census are not yet analysed, but here in this post, we'd like to share some first impressions we noted in the field, in the most severely burned patches of forest. During a recent visit (July 2023) to the northern slopes of Renški vrh/Fajti Hrib/Cerje (above the lower Vipava valley between Miren and Renče) we were amazed by the number of birds using the charred black pines for feeding. Actually the forest that most people would term as "dead" is very much alive!

Burned stands of black pine Pinus nigra on the northern slopes of Renški vrh/Fajti hrib, July 2023.

Along a 3,5 km stretch of forest road we made 5 stops/points where we listened and searched for (mostly) woodpeckers in the most fire-affected patches of forest. The "count" was not very methodological and accurate (also due to the time of visit & season), but still gave a rough idea of the importance of such severely burned forest for the local birds. Every point held at least two Great Spotted Woodpeckers Dendrocopos major, with the highest number of Great Spots counted on one point being four individuals. In the end we counted a total of 12 Great Spotted Woodpeckers which were utilising the burned trees for feeding. In addition we also observed two Black Woodpeckers Dryocopus martius feeding on the charred pines and found many signs of their bill strikes on the bark. Great Spotted and Black are the commonest species of woodpeckers in forests of black pines in the Karst, so their presence was expected, however local aggregations occur, when feeding conditions are particularly favourable, such in the case of a forest stand damaged by fire. Other less common species of woodpeckers expected to utilise this burned forest include Lesser Spotted Dryobates minor, Grey-headed Picus canus and perhaps even Green Woodpecker Picus virids which was heard on site (the latter usually strictly linked to deciduous stands).

The bark removed from a black pine Pinus nigra by a hungry woodpecker.
Feeding signs of woodpeckers on the charred trunks of black pines Pinus nigra.
Black pines Pinus nigra first hit by the fire and then by woodpeckers.
Great Spotted Woodpecker Dendrocopos major (juvenile) feeding on charred black pines Pinus nigra.
Black Woodpecker Dryocopus martius (female) feeding on charred black pines Pinus nigra.

Great Spotted & Black Woodpecker feeding on burned black pines (video).

Apart from woodpeckers there were also lots of other small songbirds feeding in the burned pine stands. Unusual species for this type of forest (if the forest would be unaffected by fire) were the numerous Black Redstarts Phoenicurus ochruros and Spotted Flycatchers Muscicapa striata, both taking advantage of the more open space in the forest created by the fire and the infinity of suitable hunting perches. However the most numerically common were birds in mixed "gangs" such as Great Parus major, Blue Cyanistes caeruleus and Coal Tits Periparus ater, Nuthatches Sitta europaea and Short-toed Treecreepers Certhia brachydactyla, plus locally also larger flocks of Chaffinches Fringilla coelebs feeding on the ground. In some places we also observed Marsh Poecile palustris and Crested Tits Lophophanes cristatus, while among the other interesting birds there was also a Goshawk Accipiter gentilis that took off from a burned stand of pines. The latter is a typical breeder of pine stands in the Karst and is one of the species that could have been affected by the loss of nesting habitat. Many of the observed birds were juveniles, as it's typical for this season. And of course only some of them were cooperative enough to be able to photograph them.

Spotted Flycatcher Muscicapa striata in burned pine forest.
Great Tit Parus major in burned pine forest.
Short-toed Treecreeper Certhia brachydactyla in burned pine forest.

And what were all these birds feeding on in such a "dead" forest? A closer inspection of some burned pine trees revealed that they were alive with bark beetles (Scolytinae), most probably Six-toothed Bark Beetles Ips sexdentatus. Other unusual insects were also present on the trunks, including the impressive shiny-blue bark-gnawing beeetles Temnoscheila caerulea (Trogossitidae) that feed by predating on bark beetles! For more on these interesting beetles see here & better photos here.

Six-toothed Bark Beetles Ips sexdentatus excavating in the bark of a black pine Pinus nigra.
Temnoscheila caerulea (a species of bark-gnawing beetle; family Trogossitidae)

Bark beetle outbreaks usually occur as a consequence of natural disturbances in the forest (fire, windfall, ice storm) that weaken the stands and make the trees more vulnerable to the attacks of various "pests". However, from an ecological point of view, such outbreaks are important events in the forest dynamics. All the invertebrates attacking the dead and dying trees provide an important food source for the local insectivorous birds. These in turn act as natural regulators of the pests' populations. Woodpeckers in particular, such as the Three-toed Woodpecker Picoides tridactylus (absent from the Karst and only found in mountain coniferous forests in Slovenia) are known to respond to such outbreaks by increasing their population (up to 44x) in forests affected by bark beetles. In turn Three-toed Woodpeckers can lower the populations of bark beetles even by 98% (check this article). In North America the Black-backed Woodpecker Picoides arcticus is almost completely dependant on stands of severely burned forest (see here). In Europe we don't really have such a specialised bird associated with burned forest, although woodpeckers clearly benefit from beetle-infested trees and many other species benefit from areas opened by the fire. In the Karst, this is the case for example with Natura 2000 species such as Ortolan Bunting Emberiza hortulana, Nightjar Caprimulgus europaeus, Woodlark Lullula arborea, Red-backed Shrike Lanius collurio and other species of endangered grassland habitats.

It remains to be seen (in the next breeding seasons) if the burned forests are also important as nesting places, or only as foraging areas for the local birds. However studying birds in the burned stands won't be easy, as few places will remain untouched. The Slovenian forestry is already making the most to remove the burned trees as soon as possible and to save the economical value of timber. Therefore now large areas already look like below... 

(why is salvage logging wrong from an ecological point of view in this video).

Salvage logging of the burned black pine forest above the lower Vipava valley near Nova Gorica.


Earlier in spring (May 2023), during our bird censuses on the fire sites, we also came across some exceptional blooms of wildflowers in the more open areas, where the fire burned the thermophilous scrub interspersed with patches of grassland. From the biodiversity point of view this is the most "problematic" habitat in the Karst, as the scrubbing over of once open areas (grasslands & hay meadows) leads to biodiversity impoverishment (lower species richness). In terms of birds, we are losing all those species of conservation priority associated with open habitats that we already mentioned above. At the same time vast areas of impenetrable scrub (with dense bushes of Smoke-tree Cotinus coggygria) or overgrown meadows promote the quick spread of flames in the event of wildfires. Therefore managing open areas with a traditonal, low intensity type of agriculture (extensive grazing & mowing) would be beneficial for biodiversity and for fighting wildfires too!

Dropwort Filipendula vulgaris on the burned ground near Brestovica pri Komnu. May 2023.
Dittany Dictamnus albus on the burned ground near Brestovica pri Komnu. May 2023.
White Laceflower Orlaya grandiflora on burned ground near Brestovica pri Komnu. May 2023.
Bloody Pink Dianthus sanguineus on the burned ground near Brestovica pri Komnu. May 2023.
Purple Mullein Verbascum phoeniceum on the burned ground near Brestovica pri Komnu. May 2023.
Amethyst Eryngo Eryngium amethystinum (with Trichodes apiarius) on Renški vrh in July 2023.

To learn more on the subject of fire ecology and species depending on wildfires, we recommend checking this informative website (and especially the videos) created by Dick Hutto, an emeritus professor in biology and wildlife biology at the University of Montana, who focused most of his research on conifer forests that have been restored by severe wildfires: Fire Ecology Story

Tuesday, 27 December 2022

2022 in Wild Slovenia

Another biodiversity-rich and wildlife-filled year has gone by. Our routine field activities have brought us to many wonderful places, most of them close to home, in the Karst and the Notranjska region of Slovenia. However this year we also spent more time abroad. In April and May we censused rare woodpeckers in the primeval forests of Plitvice National Park in Croatia. In June we went to enjoy some Lammergeiers in the Austrian Alps. In mid August I (Domen) visited Norway on a work trip, with some amazing wildlife seen along the way. And finally in early September we made a road trip to Montenegro, visiting the country's national parks, enjoying great sceneries and finding lots of interesting stuff. However we still haven't found time for detailed trip reports...
As usual, most of early spring was dedicated to censusing woodpeckers, especially Middle Spotted and White-backed, but also Three-toed later in the season. In late spring and early summer, field activity was concentrated in the Karst's limestone grasslands, either counting breeding birds or monitoring rare species such as Ortolan Bunting. Surely one of the year's highlights was seeing seven Brown Bears in one day, while searching (unsuccesfully) for nests of White-backed Woodpecker!
Time for writing blogs this year has considerably shrunk, hence we also moved most of our regular (daily or so) posting to Twitter. Not sure what the new year will bring in terms of free time. Make sure to follow us, either here or there, also in the future. In the meantime, enjoy this selection from our field activities in 2022!

Bearded Tit Panurus biarmicus, Rače fishponds, January.
Catching an Eagle Owl Bubo bubo for satellite-tagging, with my colleague Tomaž Mihelič in the Karst, January.
Wallcreeper Tichodroma muraria, Karst edge, January.
Winter in the karstic forest.
White-backed Woodpecker Dendrocopos leucotos lilfordi, Javorniki Mts., February.
Three-toed Woodpecker Picoides tridactylus, Snežnik, February.
White-tailed Eagle Haliaeetus albicilla, Cerkniško jezero, February.
Common Crane Grus grus, Karst, February.
Footprints of Brown Bear Ursus arctos, Snežnik, February.
Finding a Red Deer's antler, Snežnik, February.
Mountain beech forest on mount Snežnik, February.
Black Woodpecker Dryocopus martius, Karst, March.
Ural Owl Strix uralensis, Karst, March.
Middle Spotted Woodpecker Leiopicus medius, Karst, March.
Surveying the habitat of Middle Spotted Woodpecker in the Karst in March.
Snake's-head Fritillary Fritillaria meleagris, Ljubljansko barje, March.
Little Bittern Ixobrychus minutus, Škocjanski zatok NR, 11th March. Probably the species' earliest spring record for Slovenia.
European Tree Frog Hyla arborea, Škocjanski zatok NR, March.
Wryneck Jynx torquilla, Škocjanski zatok NR, April.
Black-throated Divers Gavia arctica in breeding plumage, on the sea at Strunjan in April.
April snow at Cerkniško jezero and on the Javorniki mountains.
Red-necked Grebe Podiceps grisegena, Cerkniško jezero, April. Very rare (extinct?) breeder in Slovenia.
Carniolan Bee Apis mellifera carnica on Christmas Rose Helleborus niger, Cerkniško jezero, April.
Taking Touty on a White-back's hunt on Snežnik (under a hailstorm) in April.
White-backed Woodpecker Dendrocopos leucotos lilfordi, Snežnik, April. Video.
Three-toed Woodpecker Picoides tridactylus, Snežnik, April.
Mountain beech forest with carpet of Wild Garlic Allium ursinum on Snežnik in April.
Spending spring in the forest meant Wild Garlic Allium ursinum was regularly added to daily meals.
Brown Bear Ursus arctos eating grass by the road, Snežnik, April.
Roe Deer Capreolus capreolus, Snežnik, April.
Rock Bunting Emberiza cia, Snežnik, April.
Birding the SW slopes of Snežnik's plateau in May.
Golden Eagle Aquila chrysaetos, Snežnik, May.
Red Deer Cervus elaphus, Snežnik, May.
Brown Bear Ursus arctos, Snežnik, May. Mother with 3 cubs.
Adder Vipera berus bosniensis (male), Snežnik, May. Video.
Red Squirrel Sciurus vulgaris, Snežnik, May.
Fox Vulpes vulpes, Snežnik, May.
Beech Fagus sylvatica, Snežnik, May.
Hacquetia Hacquetia epipactis, Karst, April.
Spring counts in the flysch hills at the edge of the Karst, May.
Fire Salamander Salamandra salamandra, SW slopes of Snežnik, April.
Egg-laying Fire Salamander Salamandra salamandra, Brkini hills, April.
Fire-bellied Toad Bombina variegata, Brkini hills, April.
Pale-flowered Orchid Orchis pallens, Karst, April.
Green-winged Orchid Anacamptis morio & Poet's Narcissus Narcissus poeticus, Karst, April.
Fly Orchid Ophrys insectifera, Karst, May.
Ophrys sulcata, Karst edge, May.
Lady Orchid Orchis purpurea, Istria, April.
Southern Festoon Zerinthia polyxena, Karst, April.
Birding the Karst's dry grasslands in April.
Short-toed Eagle Circaetus gallicus, Karst, April.
Hoopoe Upupa epops, Karst, April.
Sessile Oaks Quercus petraea in the Karst in late April.
Our local Cuckoo Cuculus canorus in the woodland behind the house, Karst, May.
Ural Owl Strix uralensis after a morning bath in a muddy puddle, Karst, May.
Centenary silver fir Abies alba in the primeval forest reserve at Plitvice NP (Croatia) in May.
Counting woodpeckers in the primeval forest at Plitvice National Park (Croatia), May.
Three-toed Woodpecker Picoides tridactylus, Plitvice National Park (Croatia), May.
Ural Owl Strix uralensis, Plitvice National Park (Croatia), April.
White-backed Woodpecker Dendrocopos leucotos lilfordi, Plitvice National Park (Croatia), May.
Collared Flycatcher Ficedula albicollis, Plitvice National Park (Croatia), May.
Alpine Salamander Salamandra atra, Jelovica plateau, May.
"Cigar" of Capercaillie Tetrao urogallus during the species' census on the Jelovica plateau, May.
Paeonia daurica, Karst, May.
Dittany Dictamnus albus & Feather Grass Stipa eriocaulis on a Karst's dry limestone grassland, May.
Jurinea mollis, Karst edge, May.
Skylark Alauda arvensis, Karst edge, May.
Red-backed Shrike Lanius collurio, Karst edge, May.
Barred Warbler Sylvia nisoria, Karst, May.
Ortolan Bunting Emberiza hortulana, Karst edge, May. One of the only 2 pairs remaining in Slovenia.
Turtle Dove Streptopelia turtur, Škocjanski zatok, May.
Golden Jackal Canis aureus, Karst edge, May.
Blue Rock Thrush Monticola solitarius, Karst edge, June.
Great Sooty Satyr Satyrus ferula, Karst edge, June.
Carniolan Burnet Zygaena carniolica, Karst edge, June.
Smoke-bush Cotinus coggygria in seed, Karst edge, June.
Lesser Grey Shrike Lanius minor, Cerkniško jezero, May.
Common Rosefinch Carpodacus erythrinus, Cerkniško jezero, May.
On the dry mountain grasslands of Nanos in late May - one of our favourite places of all!
White Asphodel Asphodelus albus & Kojnik's Iris Iris sibirica erirrhiza, Nanos, May.
Blue Rock Thrush Monticola solitarius, Nanos, May.
Carniolan Lily Lilium carniolicum, Nanos, May.
Marsh Fritillary Euphydryas aurinia, Nanos, May.
Geranium Argus Aricia eumedon, Nanos, May.
Alpine Chamois Rupicapra rupicapra, Nanos, May.
Wild Garlic (Ramsons) Allium ursinum, Nanos, May.
Looking for Red-breasted Flycatcher in the Kamnik-Savinja Alps in June.
Red-breasted Flycatcher Ficedula parva, Kamnik-Savinja Alps, June.
Dawn in the Karst's hay meadows - counting breeding birds in early June.
Red-backed Shrike Lanius collurio, Karst, June.
Juvenile Middle Spotted Woodpecker Leiopicus medius, Karst, June.
Red Deer Cervus elaphus, Karst, June.
Centenary Lime Tilia platyphyllos, Karst, June.
Karstic oak forest in early June.
Wood Warbler Phylloscopus sibilatrix holding territory in the flysch hills near the Karst in July.
Pair of Little Bitterns Ixobrychus minutus at Škocjanski zatok (from the office window) in June.
Yellow-bellied Toad Bombina variegata, flysch hills, July.
White-clawed Crayfish Austropotamobius pallipes, flysch hills, July.
Southern White Admiral Limenitis reducta, Karst, July.
Apollo Parnassius apollo, Trnovski gozd, July.
Erebia stirius, Erebia ligea & Satyrus ferula, Trnovski gozd, July. Video (with 90K views!)
Summer widlife safari in the Karst.
In July we spent a few days in the forests of Kočevje, with no current water, electricity and phone signal.
Primeval forest of Rajhenavski rog near Kočevje.
Melanistic Ural Owl Strix uralensis, Kočevski rog, July. Pic by Davide Scridel.
Alpine Longhorn Beetle Rosalia alpina, Kočevsko, July.
Alpine Chamois Rupicapra rupicapra, Kočevsko, July.
Purple Emperor Apatura iris, Kočevsko, July.
Alpine Longhorn Beetle Rosalia alpina, Javorniki Mts., July.
Ural Owl Strix uralensis, Javorniki Mts., July.
Melanistic Adder Vipera berus, Snežnik, July.
Edelweiss Leontopodium alpinum, Snežnik, July.
Golden Jackal Canis aureus, Škocjanski zatok NR, July. The species' first documented record for the reserve.
Mammal watching on Javorniki's SW slopes in July.
Zois' Bellflower Campanula zoysii, Kanin (Julian Alps), August.
Papaver alpinum rhaeticum (yellow) & Papaver alpinum ernesti-mayeri (white), Kanin (Julian Alps), August.
Pink Cinquefoil Potentilla nitida, Kanin (Julian Alps), August.
Alpine Ibex Capra ibex, Kanin (Julian Alps), August.
On the high-altitude limestone pavements of Kanin, August.
Camping next to the dormouse-infested bivouac on Breginjski Stol, August.
Alpine Longhorn Beetle Rosalia alpina, Breginjski Stol (Julian Alps), August.
Snorkeling in the river Nadiža, at the feet of mount Breginjski Stol in August.
Silver-washed Fritillary Argynnis paphia f. valesina, Snežnik, August.
Alpine Salamander Salamandra atra prenjensis, Snežnik, August.
Spurge Hawk-moth Hyles euphorbiae, Karst, August.
Bluethroat Luscinia svecica, Škocjanski zatok NR, September.
Osprey Pandion haliaetus, Škocjanski zatok NR, September.
Red Deer Cervus elaphus, Karst, September. Enjoying the rutting season very close to home.
Autumn Lady's-tresses Spiranthes spiralis, Karst, September.
Fir Coral Tooth Fungus Hericium alpestre, Snežnik, September.
Ural Owl Strix uralensis, Javorniki Mts., October. Video.
Red-rumped Swallow Cecropis daurica, Karst, October. Pair close to an active nest (very rare breeder in Slovenia)
Middle Spotted Woodpecker Leiopicus medius, Karst, October. A "km 0" Middle Spot! The first observation of the species in the woodland behind our house.
Autumn colours in the mountain beech forests of Snežnik in early October.
Tinder Fungus Fomes fomentarius, Snežnik, October.
Melanistic Ural Owl Strix uralensis, Kočevsko, November. Pics by Matteo Skodler.
Three-toed Woodpecker Picoides tridactylus, Snežnik, October.
White-backed Woodpecker Dendrocopos leucotos lilfordi, Trnovski gozd, November. Video.
Wallcreeper Tichodroma muraria, Karst, October.
Common Crane Grus grus, Škocjanski zatok NR, November.
Dipper Cinclus cinclus, river Unica, November.
Fire Salamander Salamandra salamandra, flysch hills at the edge of the Karst, December.
Ural Owl Strix uralensis, Karst, December.
Middle Spotted Woodpecker Leiopicus medius, Karst, December.