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Wetlands play a vital role in conserving waterbirds, particularly along major European river systems such as the Danube River and its tributaries. To promote the importance of wetlands and address the lack of data on bird biodiversity in aquatic ecosystems, this study was conducted to assess the baseline status of a demonstration site within the European project DaWetRest. The research focused on a lesser-studied pilot area, the Danube North of Kopački rit, near the village of Draž, located in the tri-border region of Croatia, Hungary, and Serbia. Systematic ornithological monitoring was carried out monthly from January to December 2024 across three monitoring areas (total transect length: 4200 m). A total of 26 bird taxa were recorded, comprising 2148 individual observations. The most dominant species were the Mallard (Anas platyrhynchos), Grey Heron (Ardea cinerea), and Great Cormorant (Phalacrocorax carbo). Conversely, the species that were the least present were White Stork (Ciconia ciconia), Squacco Heron (Ardeola ralloides), Great Crested Grebe (Podiceps cristatus), Eurasian Teal (Anas crecca), and Black Stork (Ciconia nigra). This study also examines the seasonal dynamics of waterbirds, providing essential baseline data for evaluating the effectiveness of upcoming restoration measures planned for the area.

This paper examines the role of transnational cooperation in conserving the ecological integrity of the Danube River through the DANUBEPARKS network of protected areas. As Europe’s most species-rich river system, the Danube connects diverse biogeographic regions, yet faces increasing pressure from habitat degradation, pollution and hydrological modifications. Recognizing the need for a unified approach, protected area administrations across the basin have formed partnerships to address shared conservation challenges. The paper traces the evolution of this collaboration from early bilateral agreements to the establishment of the DANUBEPARKS Association, a network fostering ecological connectivity and coordinated restoration. A key achievement is the development of the WILDisland concept, which identifies islands as critical habitats and indicators of riparian ecosystem health. Additionally, the network’s advocacy efforts have contributed to the formation of the Danube WILDisland Ramsar Regional Initiative, securing international recognition and policy support for long-term conservation. By bridging protected areas and aligning conservation goals across borders, DANUBEPARKS Association serves as a model for integrated river basin management. Its success demonstrates the power of trust, shared governance and cross-sector partnerships in overcoming political, economic and ecological barriers ensuring the sustainable management of one of Europe’s most vital waterways. Cross-country cooperation facilitates efficient conservation of shared natural resources. Common conservation goals unite and drive joint action across the Danube. Bottom-up initiatives evolve into sustainable structures for transnational governance. The WILDisland concept promotes islands as key habitats for river ecosystem health.

When studying the well-being and fitness of ichthyofauna in a specific area, vital information comes from length–weight relationships (LWRs) and condition factor analyses and calculations. Data were collected from 2015 to 2019 in an area important for fish shelter, feeding, and spawning. Twenty four species belonging to 10 different families were identified from the total 16,895 of caught individuals, with the most abundant species being Blicca bjoerkna. The calculation of LWRs was possible for 19 species, (R2 = 0.7049–0.9998 (p < 0.05)), with the values of the mean coefficient b ranging from 2.6831 to 3.5747, indicating an overall positive allometric growth in the fish population. The results of Fulton’s and the relative condition factors showed that a total of eight species were in a relatively good condition, although the species in question varied between the two condition factors. Fulton’s condition factor showed the highest average value for Lepomis gibbosus (1.4956), while Cobitis elongatoides had the lowest (0.4739). Contrarily, the relative condition factor showed the highest average value for Silurus glanis (1.0524), and the lowest for Gymnocephalus cernua (1.0023). The lower values of calculated condition factors in some species could be attributed to sampling being conducted during the colder months of autumn and winter. Future studies should include seasonal sampling in order to achieve a better understanding how various abiotic factors impact the condition factors of these fish species. Nevertheless, this research provided valuable data on the status of the fish population in the floodplain and could be used as a guideline for designing future ichthyofauna studies in this area.

West Nile virus (WNV) is one of the most widely distributed (re-)emerging arboviruses. In Croatia, acute WNV infections as well as seropositivity were detected in humans, horses, birds and poultry. Although serologic evidence of WNV human infections dates back to the 1970s, no clinical cases were reported until 2012. WNV outbreaks, as well as sporadic infections, were continuously recorded in continental Croatian counties from 2012 to 2018. In addition, acute asymptomatic infections (IgM antibodies) in horses have been regularly notified in continental regions since 2012, while seropositive horses (seroprevalence rates 3.7–21.4%) were detected in both continental and coastal regions. Moreover, WNV seropositivity in poultry (1.8–22.9%) was reported from 2013 to 2020. During the largest WNV outbreak in 2018, WNV RNA was detected for the first time in two dead goshawks (Accipiter gentilis) from the same aviary in North-West Croatia, while WNV antibodies were found in one buzzard (Butteo butteo) from the same region. In addition, WNV RNA was detected in a dead blackbird (Turdus merula) at the Croatian littoral. The phylogenetic analysis of 11 strains detected in urine samples of patients with neuroinvasive disease and 1 strain detected in a goshawk showed circulation of WNV lineage 2. Thus far, WNV has not been detected in mosquitoes in Croatia.

Red deer (Cervus elaphus), as a highly vocal species, provide versatile ecosystem functions beyond grazing. Their flexible use of different habitats allows them to occupy a variety of ecosystems. As global efforts to conserve biodiversity increase, there is a growing need for new approaches to continuous wildlife monitoring. Bioacoustics is a rapidly developing field that provides valuable data, especially in environments that are difficult to access. The spatial occupancy of red deer in Kopački Rit Nature Park was investigated using passive acoustic devices during the rutting season (September–October) in 2023 and 2024. A total of 332,302 recordings were collected with AudioMoth devices configured to record for 1 min every 5 min over a 10-day period. A recognition model was trained on the Arbimon platform, and a random forest model was applied to the detection data. The occupancy model revealed differences in spatial occupancy between the two years. Although none of the tested covariates showed statistically significant effects, the observed differences likely reflect unmeasured ecological dynamics, such as hydrological variability and resource availability. These findings highlight the potential of passive acoustic monitoring as a reliable, non-invasive approach for large mammal studies.

In January 2014, the first ever comprehensive winter census of the Whitetailed Eagle Haliaeetus albicilla along the Danube River was conducted, using mostly point and transect counts. Altogether, 550-700 eagles were counted. The upper range of the estimate may in fact be more realistic because 615 km of the Danube were not surveyed. Birds were observed in every country along the Danube. Hotspots of occurrences were (1) the Central Danube floodplains - the area encompassing the lower Hungarian section (Danube- Drava National Park), Kopacki rit Nature Park (Croatia), and the Gornje Podunavlje Special Nature Reserve (Serbia); and (2) the Danube Delta Biosphere Reserve. According to the Action Plan for the conservation of the White-tailed Eagle along the Danube, future winter counts should be made regularly, and lower variation in the resulting eagle numbers achieved by a higher degree of synchronization between individual countries. This study reinforces the importance of protected areas along the Danube as a backbone for the conservation of White-tailed Eagles and biodiversity.

West Nile virus (WNV) is one of the most widely distributed (re-)emerging arboviruses. In Croatia, acute WNV infections as well as seropositivity were detected in humans, horses, birds and poultry. Although serologic evidence of WNV human infections dates back to the 1970s, no clinical cases were reported until 2012. WNV outbreaks, as well as sporadic infections, were continuously recorded in continental Croatian counties from 2012 to 2018. In addition, acute asymptomatic infections (IgM antibodies) in horses have been regularly notified in continental regions since 2012, while seropositive horses (seroprevalence rates 3.7-21.4%) were detected in both continental and coastal regions. Moreover, WNV seropositivity in poultry (1.8-22.9%) was reported from 2013 to 2020. During the largest WNV outbreak in 2018, WNV RNA was detected for the first time in two dead goshawks (Accipiter gentilis) from the same aviary in North-West Croatia, while WNV antibodies were found in one buzzard (Butteo butteo) from the same region. In addition, WNV RNA was detected in a dead blackbird (Turdus merula) at the Croatian littoral. The phylogenetic analysis of 11 strains detected in urine samples of patients with neuroinvasive disease and 1 strain detected in a goshawk showed circulation of WNV lineage 2. Thus far, WNV has not been detected in mosquitoes in Croatia.