Tom 39 (2018): Zeszyt 178-179 (December 2018)

Between 1984 and 2017, 1,388 Black Kites were recorded, mostly in lowlands with 70% of observations made at Dravsko polje. They were observed from sea level to around 1,600 m a.s.l. with an average elevation of 271 m a.s.l. The species was present in Slovenia from mid-March to early December with indistinct spring and autumn migrations. The highest number of observations was recorded in May. The Black Kite was observed in 71 out of 238 10x10 km grid squares in Slovenia (29.8%), with more observations around known breeding sites and at sites with higher observer effort. Both the number of observations and the number of probable and confirmed breeding pairs increased. In 2011–2018, 10 breeding pairs were found at 7 sites (3–7 per year). Additionally, 11 probable breeding pairs at 9 sites (0–6 pairs per year) were found. The breeding population in 2011–2018 is estimated at 10–21 pairs with an average breeding density of 0.3–0.9 breeding pairs per 100 km². The highest density was recorded at Dravsko polje with 0.6–2.2 breeding pairs per 100 km². If possible breeding (breeding attempts) were also taken into consideration, the estimate would be up to five breeding pairs higher. The species was recorded at known breeding sites in most years after the breeding was confirmed. Black Kites were observed closer to larger water bodies and to rubbish tips than expected by chance. More Black Kites were recorded in areas with a lower percentage of forest and arable land and a higher percentage of meadows, settlements and wetlands.

Here we present the results of candling 258 eggs from 50 nests of Common Eiders Somateria mollissima in a colony in the central Baltic. Of these, 223 (86%) had a developing foetus. Among the 35 (14%) failed eggs, 15 were unfertilized and 20 contained a dead embryo. The prevalence of failed eggs is similar to the average proportion of failed eggs reported previously by the Christiansø Scientific Field Station during 1998–2014. The reason for the high percentage of failed eggs is unknown; however, low pre-incubation body mass and energetic stress is likely to be the main factor. In addition, we incubated 8 eggs in the laboratory from day 0 to hatch in order to follow the development and foetal morphology. This resulted in a field atlas from which it is possible to estimate date of incubation start using candling in early incubation (days 1–12). The atlas is a new possibility for field biologists to estimate the first day of incubation of breeding eiders and the prevalence of unfertilized and rotten eggs, which is important for studying their biology and population dynamics.

Here we present the recording of body mass change and weight loss during incubation in a Common Eider Somateria mollissima colony at Christiansø in the Central Baltic (55°19’N 15°11’E). The study was conducted during April and May 2015 and a total number of four birds were followed (two were lost due to predation and three due to power outages). Body mass and nesting behaviour was recorded electronically over a period of 26–27 days using automatic poultry scales and a surveillance video camera. During incubation, the eiders underwent a 28–37% loss in body mass and left the nest on average 13 times (range: 7–17 times) for a period of 7–70 min. In general, birds with high initial body mass left their nest for a shorter total time than birds with lower initial body mass. The recorded daily changes in body mass indicate that the eiders foraged during the incubation period, not just leaving the nest for rehydration or in response to disturbance, which improve our current understanding of eider incubation behaviour. Such information is important to fully understanding of eider breeding biology in order to better conserve and manage the species during its breeding seasons where individual birds undergo extreme stress that may affect reproductive outcome and adult survival.

The IBA network is being regularly updated, based on new data and their better quality. There have been three previous stages of the marine IBA identification in Slovenia and the Mediterranean Shag has been included as the qualifying species only in the most recent stage in 2011. However, the sites were limited to inshore coastal roost-sites and thus insufficient to cover the foraging areas of the species. To fill this gap in the Slovenian territorial sea, new marine IBAs have been identified for the Mediterranean Shag within the scope of the SIMARINE-NATURA (LIFE10NAT/SI/141) project in the 2011–2015 period. The new sites were identified following standardized methodology for the identification of marine IBAs from BirdLife International. The data on the Mediterranean Shag distribution and population size were collected using four field methods: (1) monthly monitoring at in-shore communal roost-sites, (2) monthly monitoring at sea following the standardized ESAS method, (3) GPS telemetry, and (4) unsystematic census of in-shore floating groups. Based on these data, one new site, the IBA Osrednji Tržaški zaliv, and one extension to the existing IBA Debeli rtič were identified, covering 8,218 ha and 155 ha, respectively. The new sites cover 39.2% of the Slovenian territorial sea.

In 2017, the Slovenian bird ringing scheme concluded 90 years of continuous ringing in the country. In 2017, we collected data on 176 bird species. We ringed 79,886 birds of 164 species, recorded 177 recoveries of birds ringed in Slovenia and found abroad, 295 foreign recoveries in Slovenia and 2,209 local recoveries. The most ringed species were the Blackcap Sylvia atricapilla and Great Tit Parus major and, among pulli in the nest, the Great Tit, White Stork Ciconia ciconia and Barn Swallow Hirundo rustica. In 2017, 12 colour ringing schemes were active in Slovenia. In the 2012-2017 period, the number of recoveries of birds ringed in Slovenia and found abroad increased significantly due to colour ringing, especially regarding the waterbirds. With colour ringing, the likelihood of recoveries is considerably greater (75.20 ± 91.36 recoveries per 100 ringed birds) than with metal ringing only (0.11 ± 0.08 recoveries per 100 ringed birds). Among local recoveries, the most frequent were the Mute Swans Cygnus olor and Common Terns Sterna hirundo, and among foreign recoveries the Black-headed Gulls Chroicocephalus ridibundus predominated. In 2017, the first Broad-billed Sandpiper Calidris falcinellus was ringed in Slovenia (Sečovlje salinas), and additional three rare species were ringed as well: the Yellow-browed Warbler Phylloscopus inornatus (Ljubljansko barje), Paddyfield Warbler Acrocephalus agricola (Ljubljansko barje) and Little Bunting Emberiza pusilla (Šentrupert).

Between 29 Mar and 10 Apr, 2015, a Little Owl Athene noctua survey was carried out using the playback method in the southern part of Montenegro. The study area was situated between the town of Ulcinj and the Bojana River delta. A total of 55 calling males were registered at 26 survey points with a maximum of 4 calling males per survey point. Considering the low response rate of the Little Owl, its local population was estimated at be 55–110 calling males. This study presents the first systematic survey of the Little Owl in Montenegro.

We examined the pellets of the Barn Owl Tyto alba, collected in Pisa, Italy, in 2012. Altogether, 219 specimens of small mammals were found in 85 pellets. The Barn Owl diet was composed of ten species of small mammals, representing three different families (Muridae, Cricetidae, Soricidae). The main prey species was the Wood Mouse Apodemus sylvaticus, followed by the House Mouse Mus musculus and the Savi’s Pine Vole Microtus savii. While the smallest of the small mammals from the area, the Etruscan Shrew Suncus etruscus, was well represented in the pellets, some larger species of small mammals were not represented at all. The reason for such result may lie in the upper limit for our Barn Owl’s prey size. Results suggest that optimal prey weight for our Barn Owl may be between 26–75 g of body mass, however, the prey can be occasionally as heavy as almost 100 g, represented by adult Rat Rattus spp. Nevertheless, our results may not reflect the true hunting strategy of the Barn Owl, but the availability of a certain food item at one point in time.