Saturday 6 March 2021

Spring return to Dinaric forests

Woodpeckers have long been our favourite study subjects. This year we'll have the opportunity to focus even more on two of our favourite species, as part of specific studies within DOPPS-BirdLife Slovenia. Domen will be mostly concentrating on the rare and endangered White-backed Woodpecker Dendrocopos leucotos ssp. lilfordi in the Snežnik forests, whereas Sara will be focusing on the habitat ecology of the Middle Spotted Woodpecker Leiopicus medius in the Karst region. Late February is the time when both species become vocally active and territories are formed, therefore when the real fieldwork begins. In the past two weeks we began with our regular visits to the Dinaric forests of mount Snežnik with the aim of localising territorial pairs of White-backed Woodpeckers Dendrocopos leucotos and their nests. There are an estimated 100-150 breeding pairs in Slovenia and finding nests of this species is far from easy. So far we located one pair and their possible nest hole in an old decaying beech in an area of heavily managed forest. The pair wasn't particularly vocal, but showed rather well, especially the male which was observed boring a rather deep feeding hole in a rotting beech. 

However spontaneous drumming (of other individuals) in the forest was not to be heard and probably the territorial activity of most woodpeckers is still a bit slow, at least in the higher elevations of the Snežnik plateau (around 1300 m and above). Nevertheless during our first visit we already heard a drumming Three-toed Woodpecker Picoides tridactylus but that was probably an exception. In a few weeks the situation should be much livelier and then we expect the more intense fieldwork.

White-backed Woodpecker Dendrocopos leucotos ssp. lilfordi (male).
White-backed Woodpecker Dendrocopos leucotos ssp. lilfordi (female).
White-backed Woodpecker Dendrocopos leucotos ssp. lilfordi. Male feeding on a decaying beech.

Old nesting holes of White-backed Woodpecker.
Managed forest with a single dead beech, where the old nests are.
Fresh feeding signs on dead beech in unmanaged forest (forest reserve).
Unmanaged forest in the higher parts of the Snežnik plateau.
A centenary Beech Fagus sylvatica on a rocky outcrop in the forest.
A lone Black Pine Pinus nigra in a very unusual site, far from all its other relatives growing in plantations down in the valley.
View from a rocky outcrop on a forest reserve in the Snežnik mountains.
In the higher parts of the Snežnik plateau (around 1300 m a.s.l.) snow still lies on the ground (around half a metre of it) and wildlife is still scarce and/or mostly silent. Here we struggled to find any White-backs at all, although the habitat looked excellent. However we were surprised by a large herd of 16 Red Deer Cervus elaphus (containing females, fawns and young males), while on a distant hill we observed a bachelor group of three males, one of which sported quite impressive antlers (see video). The signs of Red Deer were omnipresent in the forest, especially in the form of footprints in the snow, however we were surprised not to see a single Brown Bear's footprint yet. It's probably still too early for them at such elevations.
Red Deer Cervus elaphus stags.

Red Deer's droppings & footprints.
The beech trees are slowly freeing themselves of the snowy mantle.
On the other hand owls seemed to be very active. Tawny Owls Strix aluco in particular are extremely vocal at this time of year and frequently sing even during the day (although shortly). We heard at least three different males in the higher parts of the Snežnik plateau, although the habitat seemed more suitable for Ural Owl Strix uralensis. Fair enough there were also a few spontaneous hooting Urals and one even showed up nicely for a short time.
Ural Owl Strix uralensis
Forest owls this year will certainly enjoy in the great abundance of rodents. As a consequence of the extremely productive beech crop of the last autumn, (which allowed a high winter survival & large litters of rodents), the forest floor is teeming with Bank Voles Myodes glareolus... and probably other rodents too. During our last two visits we were able to see up to 50-60 voles and hear/feel many more. Wherever we stopped there was some rustling in the leaf litter and with a bit of patience, about 5-10 voles could be counted. There must have been literally hundreds in the forest all around! Not surprisingly, where the snow has already melted, the floor and forest roads were covered with beech mast.
Bank Vole Myodes (Clethrionomys) glareolus
The melting snow on the forest floor reveals...
... a carpet of beech mast, food for a large variety of animals.
But on sunny forest slopes snow is replaced by another white blanket: carpets of Christmas Rose Helleborus niger. These attractive plants are surely the first source of nectar for early pollinators (bumblebees) in the mountain forests of Slovenia and fortunately they are also very common. As the name suggests the Christmas Rose can sometimes bloom as early as December, under mild winter temperatures and warm sunshine. However the real spectacle usually begins in late February and at higher elevations it can last until the beginning of May.
Christmas Rose Helleborus niger
Lower down on the slopes of mount Snežnik, the interesting river Reka originates. It first flows through Vremska dolina, a valley connecting Ilirska Bistrica with the Karst, before disappearing underground into the Škocjan caves, only to resurface again in Italy, north of Trieste and finally flowing into the Adriatic. Vremska dolina is a place we frequently pass by when driving to Snežnik, but we only seldom stop and check the river itself. However we regularly visit the westernmost stretch of the Reka, close to where it disappears underground near Divača. During a recent visit to Reka's canyon we were surprised by the sight of two female Goosanders Mergus merganser, a bird we haven't observed yet on this river and in this part of Slovenia. Upon further investigation we realised ours is the first sighting for the species on the river Reka. Goosanders are undergoing a range expansion in Slovenia and could possibly even breed here on one of the several quieter stretches of the river, which also host suitable cliffs close to the water. The nearest nesting sites for Goosanders in the southern part of Primorska are the rivers Vipava and Soča, some 30 km away from the river Reka. Further investigation will be needed.
Quite surprisingly also a small flock of migrant Teals Anas crecca was present on the Reka, along with the more usual inhabitants like Dipper Cinclus cinclus and Grey Wagtail Motacilla cinerea. On the cliffs in the canyon we also observed a Peregrine Falco peregrinus, while the fertile shores of the river were carpeted with colourful vernal flowers.
Goosander Mergus merganser
Teal Anas crecca
River Reka.
The canyon of the river Reka near Škocjanske jame.
An old Yew Taxus baccata in the cliffs above the Reka.
Ruins of castle Školj overlooking Reka's canyon.
Mezereon Daphne mezereum
Alpine Squill Scilla bifolia
Snowdrop Galanthus nivalis
Snowdrop Galanthus nivalis & Istrian Hellebore Helleborus multifidus ssp. istriacus
White Crocus Crocus vernus ssp. albiflorus
Toothwort Lathraea squamaria
Agile Frog Rana dalmatina - frogspawn.