Wednesday 28 April 2021

Advanced forest nest-finding

What an exciting time to be outside! The breeding season of Ural Owls Strix uralensis turned out to be really promising, as predicted by the large numbers of rodents present in the forest this spring, after last autumn's abundant beech crop. At the end of last week we discovered two Ural Owl nests in natural cavities in two consecutive days! The first nest was found completely by chance (as it frequently happens), while searching for White-backed Woodpecker's nests in the Dinaric forests of mount Snežnik. A greyish tail, sticking out of the side of a large Sycamore Acer pseudoplatanus caught our attention. On closer inspection we realised we were looking at a female Ural Owl incubating the eggs (probably) in a rather small natural cavity in the tree. These owls have such a long tail that they rarely fit well into a natural cavity. Nearby was also the male which gave us a warning hoot. We took a few pics and left the owls to their nesting. After all we had another mission - to find a White-back's nest.

IMPORTANT NOTE: all photos of birds on nests in this blog were taken for scientific purposes and from a safe distance, to prevent disturbance to the birds. Equipment used included powerful superzoom cameras (up to 2000 mm) and/or digiscoping through a telescope. The stay at each nest location was minimal - only the time to take a few photos and collect some basic parameters.

Female Ural Owl Strix uralensis incubating in a Sycamore's natural cavity.
Ural Owl's habitat in the forests of Snežnik.

After an entire day of unsuccessful search for nesting signs of White-backed Woodpecker Dendrocopos leucotos ssp. lilfordi, working on foot a large and rugged forest area in the Snežnik plateau, perseverance finally paid off. In the late afternoon we came across a territorial male that brought us directly to its nest, located on a tall beech, some 12 metres from the ground. The nest was excavated almost on the very top of the tree, where the wind has broken part of the tip. The male went into the hole rather quickly and silently and didn't came out for some time, so we deduced it must have been incubating. Later we also found a female (probably its female), feeding several hundred metres away from the nest. In the next two weeks we'll concentrate more carefully on the nesting of this pair as well as try to find other active nests in the area - probably more about the subject in the future posts.
White-backed Woodpecker Dendrocopos leucotos ssp. lilfordi - male.
White-backed Woodpecker Dendrocopos leucotos ssp. lilfordi - female preening.
White-back's nesting hole, on a beech 12 metres from the ground.
The height of the nest tree.
Excellent dead wood elements in the White-back's nesting habitat.
Horvath's Rock Lizard Iberolacerta horvathi - an endemic of the SE Alps, Slovenia and NW Croatia.

The next day we were in our local forest in the Karst, where we have been regularly observing a pair of Ural Owls Strix uralensis (since 2014), already widely presented in several other blog posts. Every spring we check a nice "chimney" (a large hollow beech snag) that would serve as an excellent nesting site for owls. So far we never found anything nesting in it, although Ural Owls use the area around it. So imagine our surprise when, upon approaching the tree from a distance and taking a look with binoculars, we spotted a semi-hidden owl's head staring fiercely at us! It was a female Ural Owl on the nest... at last!! The find doesn't really come as a huge surprise as this tree is perhaps one of only 3-4 available natural cavities that might host a Ural Owl in this forest. Moreover, forest owls don't necessarily breed every year, but follow natural cycles of food abundancy. Given the huge amount of rodents roaming the forest this year, a successful breeding of the owls (or at least an attempt) was kind of expected this season. Let us hope the birds manage to breed successfully, despite nearby forestry activities!
Nevertheless this remains an important record as it represents the first confirmed breeding of Ural Owl in the Karst - a region that 200 years ago used to be almost completely treeless.
The perfect natural cavity for...
Ural Owl Strix uralensis, nesting in the Karst.
The wider oak-beech forests in the Karst, around the Ural Owl's territory, host an excellent array of other breeding birds. The traditional nest of Black Woodpecker Dryocopus martius that we usually followed through the years has been "usurped" and diligently walled by a pair of Nuthatches Sitta europea, while the former owners have moved to a nearby tree. Last week male and female Black Woodpecker were still finishing the nest and not incubating yet. This week they probably are. Other woodpeckers in the same area include Middle Spotted Leiopicus medius and Grey-headed Picus canus, as well as the commoner Green Picus viridis and Great Spotted Dendrocopos major. This year we got the impression that also Nuthatches are having an excellent breeding season (possibly due to beech mast availability & major winter survival?) as we came across 6 different nests in the course of a few days. In the developing new foliage of oaks it was also good to see and hear the first returning (although only migrant) Wood Warblers Phylloscopus sibilatrix.
Black Woodpecker Dryocopus martius, male finishing the nest.
Nuthatch Sitta europaea using an old Black Woodpecker's cavity.
Beech Fagus sylvatica - the April joy of chlorophyll explosion!
Beech seedlings are sprouting everywhere on the forest floor, even in clumps!
Sessile Oaks Quercus petraea are the last to put out their new leaves.
Middle Spotted Woodpecker Leiopicus medius
Two different Nuthatches Sitta europaea on their nests.
Male Great Spotted Woodpecker Dendrocopos major on its drumming post.
Active nest of Blackbird Turdus merula in a Black Woodpecker's feeding hole.

Finally, an extremely brief, but emotionally intense visit to our recently-found nest of Black Storks Ciconia nigra (the only known in western Slovenia), for a quick check on the breeding situation. The female was sitting on the nest and incubating, while we observed it from a strategic and distant enough position to prevent stress. Soon the fresh foliage of the nearby canopies will take over and the storks will have their absolute privacy. Hopefully we'll be able to see the fledged juveniles taking into the air in mid summer!

Black Stork Ciconia nigra
Black Stork's breeding habitat in western Slovenia.

Wednesday 21 April 2021

Slow spring... but spring, at last!

We finished the previous post with snow and we'll start this one also with snow... damn it! It's spring, but winter doesn't seem to loosen its grip, especially in the mountains. The nights and mornings are still surprisingly cold in the Karst and most of continental Slovenia. Last week we started with a raptor migration monitoring near Pivka, only a few days after the last abundant snowfalls hit the area. The 14th of April was the first sunny day after the front, so a good passage of raptors was expected. But there was around 15 cm of snow on the ground and sitting on the top of a hill for most of the day was rather chilly. Nevertheless the birds put on a good show. The first bird heard when we got out of the car was a singing Cuckoo Cuculus canorus surrounded by a completely snowy landscape! As the air warmed two Black Storks Ciconia nigra appeared one after the other, descending from the Javorniki mountains into the Pivka valley. The observation spot had a clear view over a territory of a pair of Golden Eagles Aquila chrysaetos which performed well for most of the day, usually sitting on pines or soaring above their favoured ridge. Of the local raptors there was also a Goshawk Accipiter gentilis and several Buzzards Buteo buteo & Kestrels Falco tinnunculus. Among migrants there was a good north-eastward passage of Marsh Harriers Circus aeruginosus, which numbered 12 individuals at the end of the day, as well as a single Hen Harrier Circus cyaneus seen early in the morning in the Pivka valley. A colleague counting raptors on a nearby spot also observed a couple of Pallid Harriers Circus macrourus (a rare but regular migrant) going north. Other migrant raptors included a Black Kite Milvus migrans and a Hobby Falco subbuteo. Today (April 21st) we repeated the monitoring, but the migration was rather weak and we had similar species, however we added a Griffon Vulture Gyps fulvus.

A promising spring raptor-watching session?
Mt. Nanos covered with fresh April snow.
Marsh Harriers Circus aeruginosus heading north-east.
Golden Eagle Aquila chrysaetos - the local pair nesting in front of the watchpoint.
Goshwak Accipiter gentilis
Touty joined in for some afternoon entertainment.
Last week we also checked the Black Storks Ciconia nigra in the territory where we recently found a nest (the only known nesting site in western Slovenia) - it seems breeding is going well as the female is incubating, while the male is frequently seen feeding in the meadows and soaring around the territory. Meanwhile at home, we are following the nesting of the species on some excellent live cams from Estonia (here & here) and Poland (here and here). Similarly, most Slovenian birdwatchers are now glued to their PC screens, following nesting Eagle Owls from the Karst edge. The female on the first cam is incubating one egg, while on the second cam all three eggs have hatched and the chicks are being regularly fed - do take a look, it's fun!
Black Stork Ciconia nigra
Our local Short-toed Eagles Circaetus gallicus in the Karst around Sežana are also extremely active and showy. Actually we still need to figure out how many pairs there are in our area, as we keep seeing up to 4 birds together in what usually seems like an interaction between two different pairs. The area where we see them is apparently excellent for the species and probably represents a shared hunting territory. In the photos below, a Short-toed Eagle, probably male, was observed carrying a snake in its beak for at least two hours, while soaring and chasing another individual.
Short-toed Eagle Circaetus gallicus
Mid April is also the time when we begin with farmland bird censuses in the Karst. We usually cover three transects that run through excellent areas of typical dry limestone grasslands near the villages of Rakitovec, Petrinje and Osp. The main protagonists of this habitat are Woodlark Lululla arborea, Skylark Alauda arvensis, Corn Emberiza calandra and Cirl Bunting Emberiza cirlus, Hoopoe Upupa epops, Wryneck Jynx torquilla, Linnet Linaria cannabina and Stonechat Saxicola torquatus. Among rare breeders we have already found the year's first Tawny Pipit Anthus campestris (a lot earlier than usual) and Short-toed Eagle Circaetus gallicus, while (the few remaining) Ortolan Buntings Emberiza hortulana haven't returned yet. The open areas of stony meadows with sparse bushes offer an excellent habitat also for migrant passerines like Wheatears Oenanthe oenanthe, Whinchats Saxicola rubetra and the occasional Common Redstart Phoenicurus phoenicurus. It is usually good to check carefully such "groups" of migrants as rarer surprises are possible. Last year for example we found this Black-eared Wheatear Oenanthe hispanica. This time the welcome surprise was in the form of two stunning male Rock Thrushes Monticola saxatilis: one on April 16 near Rakitovec and the other on April 19 near Osp. Although this species does breed locally along the Karst edge, our observations probably involved migrants. Rock Thrush is an otherwise scarce breeder of rocky grasslands in the mountains and hills of western Slovenia.
In the thermophilous scrub of some areas along the Karst edge it is also possible to see Subalpine Warbler Sylvia cantillans, a rare breeder in Slovenia, confined to the SW of the country. We were lucky with a nice pair showing well by the side of the road, while a large flock of Alpine Swifts Apus melba and Common Swifts Apus apus swirled overhead. Although the first Nightingales Luscinia megarhynchos arrived in the Karst already on the first days of April, they kept quiet (probably due to the cold) and only now they can be heard singing more vigorously. Spring has finally arrived... at last!

Rock Thrush Monticola saxatilis - bird 1 near Rakitovec.
Rock Thrush Monticola saxatilis - bird 2 near Osp.
Woodlark Lullula arborea
Skylark Alauda arvensis
Corn Bunting Emberiza calandra
Wheatear Oenanthe oenanthe
Whinchat Saxicola rubetra
Common Redstart Phoenicurus phoenicurus
Subalpine Warbler Sylvia cantillans
Alpine Swift Apus melba
Nightingale Luscinia megarhynchos
Hoopoe Upupa epops
Wryneck Jynx torquilla

On the botanical front, the main attraction of dry karstic grasslands at the moment is the beautiful and rather rare Narrow-leaved Fritillary Fritillaria orientalis (F. tenella). When roving around the meadows we usually find only a few plants here and there, although some sites can be particularly rich with them. It is actually interesting to note that we have a small population of this species in the pine-oak woodland behind our house, which clearly used to be grassland a century ago (like most of the Karst). The few remaining plants are really struggling and only a few manage to bloom every spring. Although today we can find them in woodland, they remind us (along with the occasional Narcissus poeticus, Neotinea tridentata ect.) what most of the Karst used to be in the past. 
Back in the open meadows, the first Green-winged Orchids Anacamptis morio, Poet's Narcissuses Narcissus poeticus, Trieste Gentians Gentiana verna subsp. tergestina and several others are appearing, while the omnipresent Mountain Pasqueflowers Pulsatilla montana are already saying goodbye for this year.
Narrow-leaved Fritillary Fritillaria orientalis - out in the open meadows.
Narrow-leaved Fritillary Fritillaria orientalis - in the woodland (ex pastures) behind our house.
Green-winged Orchid Anacamptis morio
Trieste Gentian Gentiana verna ssp. tergestina
Dry limestone grasslands by the Karst edge.
Active pasture in the Karst's limestone grasslands.
From limestone grasslands to the Adriatic sea.
View NW with the Karst edge on the right and the city of Trieste & Adriatic sea in the far back.

Meanwhile on the coast, Sara has been enjoying spring wildlife at Landscape Park Strunjan, among breeding Kentish Plovers Charadrius alexandrinus and farmland birds, migrants and the first blooming orchids. She actually found two nests of Kentish Plover in the salinas a few weeks ago, but during the recent rainfalls and floods, the birds seemed to have abandoned the nests. Nevertheless the record represented a new breeding (attempt) of the species after 11 years of absence at this site! Strunjan is one of only three sites (together with Sečovlje salinas and Škocjanski zatok) where the species' breeding has been recorded in Slovenia. On the migrant front she managed to photograph a stunning Hobby Falco subbuteo eating its prey on a branch above Strunjan's famous cliffs, with the Adriatic sea as a backdrop! 
Kentish Plover Charadrius alexandrinus (incubating in the 2nd pic).

Hobby Falco subbuteo with prey.
Cirl Bunting Emberiza cirlus
Serin Serinus serinus
Swallow Hirundo rustica
Lady Orchid Orchis purpurea
Early Spider Orchid Ophrys sphegodes


Škocjanski zatok also hosted some interesting birds recently, mostly spring migrants stopping on their way to northern Europe. A Bittern Boaturus stellaris has been present for several days, after its strange absence in winter. Glossy Ibis Plegadis falcinellus, White-winged Tern Chlidonias leucopterus and Savi's Warbler Locustella luscinioides were also the major highlights over the past few days. For the complete list of the most recent interesting observations check here.

Bittern Botaurus stellaris
Glossy Ibis Plegadis falcinellus

Last but not least, an interesting botanical find. While roving in the oak-beeck forests of the Brkini hills, Domen stumbled upon a very familiar but highly unexpected plant, the charismatic Henbane Bell Scopolia carniolica. This species, one of the emblems of Slovenian botany (named after the region of Carniola and a plant with a very rich history) is mostly distributed on the Dinaric mountain chain and along its eastern border (central and southern Slovenia). This find in the Brkini region represents a new locality for the species in Slovenia and surely the southwesternmost point of its distribution in the country. The stand containing several hundred plants, in fine bloom at the moment, grows in a small wooded and rather moist gulley, a typical site for this amazing member of the family Solanaceae. The plant is extremely poisonous (it is after all a close relative of the Deadly Nightshade Atropa belladonna) and not even pollinators are immune to its toxic properties. As the last photo shows, bumblebees can be sometimes seen having difficulty taking off after drinking nectar from this plant!

Henbane Bell Scopolia carniolica
Scopolia carniolica - in the habitat.
An intoxicated bumblebee after a drink on Scopolia.