Abstract The first national Corncrake Crex crex survey in Slovenia was performed in 1992/93, followed by further five in 1999, 2004, 2010, 2015 and 2020. In 2004, annual monitoring of eight most important Corncrake Natura 2000 sites (SPAs) began. Both datasets showed a moderate population decline since 1992. After Slovenia’s accession to the EU in 2004, Corncrake population steeply declined at SPA Breginjski Stol and moderately declined at SPA Dobrava - Jovsi due to scrub encroachment, whereas moderate decline at SPA Ljubljansko barje can be attributed mostly to intensive grassland management and the conversion of grasslands to arable land, resulting in nest and habitat destruction. In 2020, the number of calling males in Slovenia was smaller by 55 % compared to 1999, when the highest number ever was recorded (683). The highest average number of Corncrakes in the 1992–2021 period was counted at SPA Ljubljansko barje (139 calling males/year), whereas the smallest number was recorded at SPA Snežnik - Pivka (8 calling males/year). A comparison of target values for Corncrake population size on individual SPAs from the national Natura 2000 management programme for the 2015–2020 period with counted population sizes showed that, with the exception of SPA Lake Cerknica, all SPAs are falling behind the target values by 32–90%, depending on the site. Likewise, the majority of sites are far from reaching target values for the enrolment of agri-environmental measure VTR (first cut after 1 Aug). The article also discusses the weaknesses of current VTR, its reform in 2021, as well as other potential measures and financial sources for Corncrake conservation.

Abstract In 2018 and 2019, the breeding success of two Common Tern colonies on artificial lakes near the River Sava in Zagreb, Croatia, was studied. The colonies were visited weekly from May to July and we collected data on phenology, number of breeding pairs, clutch size as well as egg and chick survival. We also conducted a comparison between early and late breeders. Hatching and fledging success was within previously observed ranges, apart from a low hatching success on Siromaja in 2019. The smaller colony on Siromaja had a higher productivity in both years than the colony on Rakitje, although in 2018 an avian pox virus killed much of the late chicks on Rakitje. Early breeders seem to have had higher hatching success and average clutch size. Furthermore, a greater proportion of them managed to hatch all their eggs compared to late breeders, but the differences were not statistically significant. Our study provided baseline data for future monitoring of phenology and breeding success with regard to the management of breeding colonies.

Abstract Morphometric data on Common Terns breeding in Croatia and Slovenia are presented herewith for the first time. 130 breeding adult Common Terns Sterna hirundo were measured between 2016 and 2019 along the Sava and Drava Rivers. Sex was determined for 53 birds: 22 males and 31 females. Significant sexual differences were found for head and bill length, length of bill to skull, and bill depth. Croatian and Slovenian terns had slightly shorter wings and tails compared to birds from the Netherlands, Germany and England and were lighter than birds from Germany and Italy. Head, bill and tarsus lengths were similar to those in north European populations. Contrary to results from Scotland, in our studied population, birds with head and bill lengths >79.0 mm could not be sexed as males reliably.

Abstract An overview of the long-term (1980–2019) population development of colonial Laridae species in continental part of Slovenia, their nest sites at anthropogenic water bodies, and various conservation measures with special focus on Common Tern Sterna hirundo along the Slovenian/border part of the Drava River is given. Breeding of these species occurs only on the westernmost fringes of the Pannonian plain, on lowland floodplains of the main rivers of the Danube Basin. Altogether, breeding of Common Tern and Black-headed Gull Larus ridibundus was recorded at 11 and 10 sites, respectively. Lake Ptuj is the single site with mixed-species colony residing there in all years of the study period, while at Ormož (two sites) it was established during the early 1990s in the Slovenian territory but moved completely to the Croatian side by the second half of the 2010s. At all other sites, a suitable breeding habitat became available or was provided by management in just a few years, or created only recently. The percentage of Common Tern national population breeding in continental Slovenia was usually well above 50% throughout the 1980s and 1990s (52–136 pairs), while in the last 16 years (77–258 pairs) it ranged between 40.8% and 69.0%. Breeding of Black-headed Gull remains largely limited to continental Slovenia. Overall, continental populations of both species in the last few years have been substantially higher compared to the most of the study period. Long-term trends were estimated as a moderate increase for Common Tern and a strong increase for Black-headed Gull. Since 2006, the Mediterranean Gull L. melanocephalus has been a regular breeder at Lake Ptuj (up to 28 pairs), the only such site in Slovenia. Three general types of conservation measures implemented at different nesting locations are described in detail: (1) measures to create/increase the total surface of breeding habitat – the construction of new breeding structures, such as artificial islands and nesting rafts, (2) measures to maintain and enhance breeding habitat through recurring management activities, and (3) measures aimed to increase chick/nest survival and improve breeding success.

Abstract 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.

Abstract For evaluating the current status of Citrine Wagtail Motacilla citreola in Montenegro, all available sightings were compiled from published and unpublished personal sources. A hitherto hardly known record of the species for the country by a holiday group of British birdwatchers, under the guidance of renowned ornithologist Bob Scott (1938–2009), dates from May 1982. The sighting in the Ulcinj Salina, in 1982, constitutes the first record of Citrine Wagtail in Montenegro and in the Western Balkans. More than 30 years later the species was sighted, between 2013 and 2017, again in the Ulcinj Salina (May 2013, Mar 2016, Nov 2017) and in the former Tivat Salina (Apr 2014). Hence, five observations are currently on record for Montenegro.

Summary In 2017, the International Waterbird Census (IWC) was carried out in Slovenia on January 14 and 15. Waterbirds were counted on all larger rivers, along the entire Slovenian Coastland and on most of the major standing waters in the country. During the census, in which 235 observers took part, 413 sections of the rivers and coastal sea with a total length of 1,427 km and 200 other localities (164 standing waters and 36 streams) were surveyed. The census was characterized by harsh winter conditions and high proportion of frozen water bodies. Altogether, 51,790 waterbirds of 61 species were counted. Thus, the number of waterbirds and the number of species recorded were close to the 21-year average. The highest numbers of waterbirds were counted in the Drava count area, i.e. 20,064 individuals (38.7% of all waterbirds in Slovenia). By far the most numerous species was Mallard Anas platyrhynchos (46.1% of all waterbirds), followed by Coot Fulica atra (6.8% of all waterbirds), Cormorant Phalacrocorax carbo (5.9% of all waterbirds), Black-headed Gull Chroicocephalus ridibundus (5.7% of all waterbirds) and Mute Swan Cygnus olor (3.9% of all waterbirds). The number of 1,000 counted individuals was also surpassed by Yellow-legged Gull Larus michahellis, Teal An. crecca, Tufted Duck Aythya fuligula, White-fronted Goose Anser albifrons, Pygmy Cormorant P. pygmeus and Grey Heron Ardea cinerea. Among the rarer recorded species, the Red-breasted Goose Branta ruficollis (registered for the first time during the January Waterbird Censuses and only for the third time ever in Slovenia) and Barnacle Goose Branta leucopsis (the first probable A category individual for IWC and Slovenia) deserve special mention. Numbers of the following species were the highest so far recorded during the IWC: Mandarin Duck Aix galericulata (together with 2006 and 2012), Pintail An. acuta, Ferruginous Duck Ay. nyroca, Long-tailed Duck Clangula hyemalis (together with 2003), Goosander Mergus merganser, Pygmy Cormorant, Herring Gull L. argentatus and Caspian Gull L. cachinnans. Number of Pochards Ay. ferina was the lowest so far recorded during the IWC.

Abstract In 2006–2017, annual censuses of breeding bird species regarded as indicators of natural rivers were carried out on the 38.9 km long lowland stretch of the Drava riverbed between Maribor and Zavrč with altered flow regime due to the operating hydropower plants. Gravel bar habitats were surveyed in four years of the study period by combining orthophoto analysis and analysis of field photographs. Effects of gravel bar management were evaluated based at 20 locations. The Little Ringed Plover Charadrius dubius occurred on 39.8% of the gravel bars, but most were occupied only in a few years and held just one breeding pair. Low numbers between 2009 and 2012 (< 30 pairs) were followed by a steep population increase from 2014 onwards to a maximum of 66–73 pairs (1.7–1.9 p/km). Such population dynamics was attributed to the lack of large discharges (>500 m3/s) and consequent overgrowing of riverbed in the first part of the study period, while the increase in the second part was due to the creation of extensive shingle areas (from 20,6 ha in 2009/10 to 37,8 ha in 2014) by the extreme flood in early November 2012, subsequent regular occurrence of large discharges outside the breeding seasons and large-scale removals of woody vegetation. Breeding population of Common Sandpiper Actitis hypoleucos remained at a rather similar low level (<20 p) during most of the period studied after an initial decline, and did not reflect changes in the overall surface area of riverbed habitats. Contrary to the general situation, the number of breeding pairs on gravel bars subjected to management increased several-fold. Maximum number of pairs on these bars was reached up to four years after the initiation of management measures, as only then the optimal mosaic of early successional stages interspersed with shingle areas developed at main sites. The species was widespread only on lower part of the Drava. Kingfisher Alcedo atthis was fairly widely distributed along the riverbed, but occurred in rather low densities throughout (c. one pair on 2–3 km of the studied riverbed on average), probably as a result of limited bank erosion and consequent overgrowing/lack of suitable nest sites. The population was estimated as stable with effects of harsh winter conditions on breeding numbers in some years. The majority of nest holes were excavated in eroded river banks along the main river channel (77.8%), followed by similar sites located in mouth areas of small tributaries of the Drava (14.8%). Regular breeding of Sand Martin Riparia riparia since 2012 (up to 259, mostly at only one location annually) was almost exclusively the result of the annual artificial nest site preparation programme. Fairly large gravel bar-breeding population of White Wagtail Motacilla alba, monitored since 2013 and predominantly ground nesting in sparsely vegetated areas, seems unusual considering the prevalent breeding habits of the species at the European scale. Conservation implications and guidelines for future management efforts are discussed.

Abstract In 2016, data on 176 bird species were gathered during bird ringing activities in Slovenia. A total of 65,711 birds of 165 different species were ringed. Furthermore, 148 recoveries of birds ringed in Slovenia and found abroad, 245 foreign recoveries in Slovenia and 1840 local recoveries were made. The most frequently ringed species was the Blackcap Sylvia atricapilla. Among the ringed nestlings, Great Tits Parus major, Tree Sparrows Passer montanus and White Storks Ciconia ciconia predominated. Considering recoveries of birds ringed or found abroad, the most frequent were finds based on colour rings, especially of Black-headed Gulls Chroicocephalus ridibundus, Mute Swans Cygnus olor and Common Terns Sterna hirundo. As far as local recoveries are concerned, most data were collected for Great Tit and Siskin Spinus spinus. Among rare species, two Yellow-browed Warblers Phylloscopus inornatus were ringed, one Paddyfield Warbler Acrocephalus agricola, one Little Emberiza pusilla and one Black-headed Bunting Emberiza melanocephala, the latter as a singing male, which probably also bred in 2016. The catch frequency of the Yellow-browed Warblers has indeed been increasing in Slovenia in the last 25 years, but this is still a rare and irregular vagrant on autumn migration.

Abstract In 2015, we used the same method as in the 1989-1996 period to count calling males of the Common Quail Coturnix coturnix in selected 1x1 km squares of Ljubljansko barje (central Slovenia). We counted 39 males, which is 87% less compared to the survey 20 years ago. Quails were found in 56% fewer squares. Since Quail populations are known to fluctuate greatly between years, we think that the most realistic long-term estimate for population decline would be somewhere between 50 to 90%. We detected that within only one week males stopped calling in some squares, while in others they began calling although they had not been detected there before, indicating possible relocations. This dynamics should be considered when designing a population monitoring protocol for the Quail.