Tuesday 31 March 2020

Springtime excitement

Spring is a busy period for us field biologists and the new season is just kicking in. On Sunday we went to monitor the rare White-backed Woodpecker Dendrocopos leucotos in the Javorniki mountains. We repeated last year's very successful census (when we discovered 7-8 White-backs). This year we "only" found 4 birds, including two drumming spontaneously and a rather silent pair. The beech forest habitat where the species lives has been heavily exploited by the timber industry in the last months. Probably because of this, several points were without White-backs. Nevertheless we enjoyed in the sight and sound of this territorial male:
Male White-backed Woodpecker Dendrocopos leucotos, Javorniki Mts.
Calling female White-backed Woodpecker Dendrocopos leucotos, Javorniki Mts.
Heavy logging machinery in the middle of a White-backed Woodpecker's territory.
Nearby also a pair of Ural Owls used to breed.

When we were about to finish the census our colleagues Mitja and Katarina Denac alerted us that earlier in the morning they found a Dotterel Charadrius morinellus in a karstic meadow near Divača. As the place was on our way back home, we gave it a try. After scanning the fields we soon found the bird, although it was very distant. So we approached and after some minutes could enjoy the bird at close quarters. Dotterel is a regular but rare and difficult-to-see migrant in Slovenia. As it breeds in the arctic tundra, it usually chooses open grassland and rocky areas as stopover sites. Luck is always needed with this particular species: the bird might be present one day, but vanishes overnight, therefore twitching isn't always an option. Although there are some traditional stopover sites, these need to be worked on a daily basis to guarantee success. Only a few Dotterels are observed in Slovenia every season, with most observations in early autumn, while spring sightings are fewer. With this species we were only lucky twice before (see here), both times on on mount Vremščica.
Dotterel Charadrius morinellus, Divača
(Huge thanks to Mitja and Katarina!).

Meanwhile other migrants are also returning from Africa. Recently we had several exciting season's firsts like: Short-toed Eagle Circaetus gallicus (2), Wryneck Jynx torquilla, Northern Wheatear Oenanthe oenanthe and Blue Rock Thrush Monticola solitarius in the Karst as well as Yellow Wagtail Motacilla flava, Alpine Swift Apus melba and White Stork Ciconia ciconia at Škocjanski zatok NR. There's also a good north-eastward passage of Marsh Harriers Circus aeruginosus, while the occasional Swallow Hirundo rustica and House Martin Delichon urbicum flying overhead always cheers us up. On the other hand there are still typical winter guests around like small flocks of Redwings Turdus iliacus roaming the karstic woodlands or the 40 or so Hawfinches Coccothraustes coccothraustes mixed with Siskins Spinus spinus still feasting on sunflower seeds in our garden.
Short-toed Eagle Circaetus gallicus, Karst.
Wryneck Jynx torquilla, Karst.
Northern Wheatear Oenanthe oenanthe, Karst.
Hawfinch Coccothraustes coccothraustes in the garden, Karst.

During an afternoon walk we investigated some excellent areas of oak and beech forest on the eastern edge of the Karst and counted no less than 8 (spontaneous) territorial Middle Spotted Woodpeckers Dendrocopos medius. This observation is extremely interesting because the area was already included in an acoustic census of the species back in 2016 and no Middle Spots were recorded there. A similar fact has been noted in several other sites around the Karst, suggesting a very recent colonisation of these areas by the species. Moreover last week a colleague confirmed 3 new territories in a woodland near Nova Gorica (an absolutely new site). Middle Spotted Woodpecker in western Slovenia is indeed becoming commoner year after year.
Middle Spotted Woodpecker Dendrocopos medius, Karst/Vipava valley.

As expected, at the moment there's also plenty of wildflowers to enjoy. New spring species come into bloom one after the other, especially on the dry karstic meadows, where the real show has yet to begin. One interesting habitat in early spring are the karstic dolinas - depressions formed by the erosion of limestone, commonly found all over the Karst. Some of these dolinas are very large and have steep limestone cliffs, where alpine species of plants such as Bear's Ear Primula auricula grow as ice age relicts. Last week we also visited some famous "Mediterranean islands" - limestone blocks in the otherwise sandstone Dragonja valley (in Slovenian Istria), where very rare Mediterranean species grow. These species are actually rare on a Slovenian level, but otherwise commonly found in other Mediterranean region; here they reach their northern edge of distribution. One such example is the beautiful Broad-leaved Anemone Anemone hortensis - absolutely stunning at this time of year! Other good wildlife seen recently include Dalmatian Algyroides Algyroides nigropunctatus and Nettle-tree Butterfly Libythea celtis, as well as many other butterflies.
Bear's Ear Primula auricula, Karst.
Mountain Pasqueflower Pulsatilla montana, Karst.
"Southern Lungwort" Pulmonaria australis, Karst.
Cornelian Cherry Cornus mas, Karst.
Bumblebee on Drooping Bittercress Cardamine enneaphyllos, Karst.
Dog's-tooth Violet Erythronium dens-canis, Karst.
Mezereon Daphne mezereum, Karst.
Nettle-tree Butterfly Libythea celtis, Karst.
Small Copper Lycaena phlaeas, Dragonja valley.
Dalmatian Algyroides Algyroides nigropunctatus, Karst.
Oil Beetle Meloe sp., Karst.
Limestone cliffs in the Dragonja valley.
Broad-leaved Anemone Anemone hortensis, Dragonja valley.
Wet cliffs by the river Dragonja with Maidenhair Fern Adiantum capillus-veneris.
Black Spleenwort Asplenium adiantum-nigrum, Dragonja valley.
Ground Pine Ajuga chamaepitys, Dragonja valley.
Prickly Juniper Juniperus oxycedrus, Dragonja valley.
Early Spider Orchid Ophrys sphegodes, Dragonja valley.

Thursday 26 March 2020

Rare plants in Krakovo primeval forest

Last weekend we were in the beautiful Krakovo forest (Krakovski gozd) after several years from our last visit. For us this is a magical place as it represents the only semi-natural lowland riparian forest left in Slovenia; therefore we like to call it "Little Białowieża". We usually visit it once every couple of years and the area never disappoints us; this time was no exception! Apart from discovering what looks like the first leucistic Ural Owl for science, we also enjoyed in the other typical wildlife of the forest, especially plants. Krakovski gozd is the last largest remnant of lowland alluvial forest in Slovenia and is thus extremely important for the conservation of some nationally rare plant and animal species. Speaking about birds there are two species that in Krakovski gozd reach very high population densities: Middle Spotted Woodpecker Dendrocopos medius and Collared Flycatcher Ficedula albicollis. Among others there are also breeding White-tailed Eagle Haliaeetus albicilla, Black Stork Ciconia nigra and Ural Owl Strix uralensis. Due to vast flooded forest areas this is also a paradise for amphibians, including large populations of the endangered Moor Frog Rana arvalis. The predominant forest types include two lowland oak-hornbeam associations (Pseudostellario-Quercetum and Pseudostellario-Carpinetum)  and alder riparian forest (Carici brisoides-Alnetum glutinosae). The most interesting part of Krakovski gozd is the primeval forest reserve - a small (40,5 ha) area of almost-natural forest, excluded from forestry activities in 1952 and left to its natural development. Due to the large amounts of dead timber this is a paradise for woodpeckers and secondary cavity-nesters.
Primeval oak-hornbeam forest at Krakovski gozd

Despite the fact that some of the summer migrants (like Collared Flycatcher) haven't returned yet to Krakovski gozd, the place is still worth a visit at this time of year. The vernal flora of the woodland floor is amazing and among the many common species there are several botanical delights to enjoy. The absolute highlight among plants is certainly the rare Snake's-head Fritillary Fritillaria meleagris, an endangered species of wet meadows and flooded forests. Krakovski gozd represents one of the few sites where this plant can still be found in Slovenia. However there are other botanical rarities of lowland forest and wet meadows such as Bog Violet Viola uliginosa, Dacian Lungwort Pulmonaria dacica and Belgian Gagea Gagea spathacea to name just a few we saw.
Snake's-head Fritillary Fritillaria meleagris
Flooded oak-hornbeam forest.
Bog Violet Viola uliginosa
Belgian Gagea Gagea spathacea
Dacian Lungwort Pulmonaria dacica
Goldilocks Buttercup Ranunculus auricomus
European False Stitchwort Pseudostellaria europaea
Marsh Marigold Caltha palustris
Alternate-leaved Golden Saxifrage Chrysosplenium alternifolium
Wood Sorrel Oxalis acetosella
Lesser Celandine Ficaria verna (ex Ranunculus ficaria)
Wood Anemone Anemone nemorosa
Early Dog Violet Viola reichenbachiana
Hornbeam Carpinus betulus

Early spring is also ideal for woodpeckers as most species are highly territorial when the trees are still leaf-less. During our visit we counted no less than 15 different Middle Spotted Woodpeckers Dendrocopos medius, especially at the edges of the primeval forest, where the oaks are very old and really huge. It was nice to hear their distinctive song - a "mewing" they produce only in spring and one they use instead of drumming (which is almost unknown in this species). Among other birds we also had Black Dryocopus martius, Grey-headed Picus canus & Lesser Spotted Woodpecker Dendrocopos minor, Goshawk Accipiter gentilis, Tawny Owl Strix aluco, Short-toed Certhia brachydactyla & Treecreeper Certhia familiaris and other commoner species. There were also several butterflies around, among which the commonest in the forest were Orange-tips Anthocharis chardamines frequently seen feeding on their larval food plants (Cuckooflower Cardamine pratensis and Trifoliate Bittercress Cardamine trifolia).
Middle Spotted Woodpecker Dendrocopos medius
Feeding signs of Black Woodpecker Dryocopus martius
Orange-tip Anthocharis cardamines on Trifoliate Bittercress Cardamine trifolia
Comma Polygonia c-album

More about lowland riparian forests in Slovenia here.

Sunday 22 March 2020

White Ural Owl - first case of leucism in this species!

Yesterday we went to Krakovski gozd (Krakovo forest) in eastern Slovenia and made an exceptional find. As we were walking in the lowland forest (more about this place in the next post), a pure-white bird flying among the trees in the distance caught our attention. At first we though of a small egret, but seeing its shape and jizz we soon realised it was an owl. When it landed in a tree we raised our binoculars and gazed at an all-white Ural Owl Strix uralensis! We immediately took some photos, but the bird soon flew. Fortunately Ural Owls seldom fly far, so we were soon able to relocate it and take some better images. On closer inspection we realised it had dark eyes and "normal" coloured bill, thus excluding an albino bird (which should have red eyes and pale bare parts and would also be extremely rare). Instead this looked like a leucistic bird - an individual lacking melanin pigment in the feathers, resulting in an all-white appearence (here you can read about the difference between albinism and leucism). Later at home we got the confirmation from European owl experts that this was indeed a completely leucistic Ural Owl and the FIRST to be EVER recorded!! Several cases of complete leucism are known from various owl species, including some closely-related to Ural like (North American) Barred Strix varia and Great Grey Owl Strix nebulosa. Given the rarity of the record, we intend to publish a paper on our find, so we hope you'll be able to read more on the subject in the future.
On the other hand, another form of plumage abnormality is quite commoner among macroura Ural Owls - melanism (dark plumage). This is present in about 5-15% of the Slovenian Ural Owl population and is well discussed in this excellent article by Al Vrezec, Slovenian foremost expert on the species.