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Water birds play a crucial role in disseminating and amplifying avian influenza viruses (AIVs) in the environment. However, they may have limited interactions with domestic facilities, raising the hypothesis that other wild birds may play the bridging role in introducing AIVs into poultry. An ornithocoenosis study, based on census-transect and camera-trapping methods, was conducted in 2019 in ten poultry premises in northeast Italy to characterize the bird communities and envisage the species that might act as bridge hosts for AIVs. The data collected were explored through a series of multivariate analyses (correspondence analysis and non-metric multidimensional scaling), and biodiversity indices (observed and estimated richness, Shannon entropy and Pielou’s evenness). The analyses revealed a high level of complexity in the ornithic population, with 147 censused species, and significant qualitative and quantitative differences in wild bird species composition, both in space and in time. Among these, only a few were observed in close proximity to the farm premises (i.e., Magpies, Blackbirds, Cattle Egrets, Pheasants, Eurasian Collared Doves, and Wood Pigeons), thus suggesting their potential role in spilling over AIVs to poultry; contrarily, waterfowls appeared to be scarcely inclined to close visits, especially during autumn and winter seasons. These findings stress the importance of ongoing research on the wild–domestic bird interface, advocating for a wider range of species to be considered in AIVs surveillance and prevention programs.

The aim of the paper is to examine the temporal and spatial changes observed over a 25-year period in the waterbird community nesting in the largest coastal lagoon around the Mediterranean; to examine driving factors for the observed changes; to address the most urgent conservation actions. Published sources and field surveys made between March and July were used to assess number of breeding pairs of the commonest waterbirds in 1990-1992, 2000-02 and 2012-14. The breeding waterbird community exhibited several changes in its structure, with an overall positive trend; the number of species increased from 14 to 25 and the mean yearly abundance increased from 6155 to 14,008 pairs. The diversity (H') increased slightly, whereas similarity indices and nMDS ordination both highlighted clear differences between 1990 and 1992 and 2012-2014 communities. The increase in richness and abundance were mostly due to the immigration of birds from nearby wetlands, to the partial recovery of lagoon ecological conditions since the end of the 1980s and to the occurrence of suitable man-made habitats, such as fish farms, dredge islands and a constructed wetland. The fraction of the population nesting at artificial sites and fish farms increased from 50% in 1990-1992 till 80% in 2012-2014, highlighting the importance of artificial breeding sites in costal lagoons. At the opposite natural nesting habitats, such as saltmarshes and beaches are losing importance for breeding waterbirds, thus requiring urgent conservation measures.

Since the beginning of this century, Greater Flamingo [Phoenicopterus roseus] flocks have been observed regularly when feeding in the large extensions of shallow bottoms in the Lagoon of Venice (NE Italy), the largest lagoon along the Mediterranean. Nowadays thousands of flamingos are present throughout the year. Between 2013 and 2017 I collected data on the environmental features of the shallow bottoms used by feeding flocks, along with measurements of flight initiation distance (FID) of Greater Flamingo in response to the approach of boats and pedestrians. Shallow bottoms were shown to be used when covered with approximately 10 to 60 cm of water. All the feeding sites were in open landscapes, with low occurrence of saltmarshes in a radius of 500 m. The bottoms were barely covered with seagrasses (<4% of the surface around the survey points) and were mostly silty. Feeding flocks were on average 1.2 km far from the nearest road or dyke, while the mean distance from channels that could be used by boats was about 420 m. The mean FID caused by boats or pedestrians was 241 m ± 117 m (N = 31, ± 1 SD) without significant differences between those for the two disturbance sources. The use of shallow bottoms by the Greater Flamingo appears governed primarily by the tidal cycle, but boat disturbance probably modifies this effect. According to FID values, a set-back distance of 465 m is suggested to reduce the disturbance caused by boats and pedestrians to the flamingo feeding flocks.

Each year between 1989 and 2008, I monitored Common Tern colonies in the lagoon of Venice (Italy). This population nests only on salt marsh islets, which are subjected to flooding during high tides. The number of breeding pairs decreased significantly from 832 to 109, with an average rate of decrease of −10.1%. Overall, 188 colonies were found, ranging from two to 583 pairs; median colony size was 57 pairs, and it decreased significantly. The mean turnover rate was high at 41.5%, and it ranged each year between 7.7% and 60%. The observed trends could be attributed to the increase in mean sea level that occurred over the last 20 years (0.5 cm/yr). In the May–June period, the number of days with high tides leading to a complete flooding of the breeding site increased. Between 1989 and 1998 there was on average 4.4 days with floodings. This increased to 8.4 days between 1999 and 2008. Therefore, sea level rise could be a major contributor to declining Common Tern populations in the lagoon of Venice.

Salt marshes are wet environments at the transition between land and sea, which are inhabited by species that are adapted to stressing environmental factors, such as frequent tidal inundations and highly variable salinity. The rapid and global disappearance of these ecosystems results in the loss of those species that here have their typical habitat. In the lagoon of Venice, a programme for the protection of the surviving salt marshes was initiated by building dredge islands in the framework of more comprehensive restoration work. The ecological characterisation of these man-made habitats was studied through analysing the beetle fauna established on six dredge islands with different topographical traits. Beetle assemblages were evaluated by analysing species richness and abundance. The observed species were arranged in ecological groups and within sub-habitats, delimited according to the zonation of halophytes and ruderal vegetation. Both the composition and distribution of the beetle assemblages were strongly affected by the soil elevation, which determines the salinity gradient and the flooding rate. Hygrophilous and halobious taxa were dominant; however, many generalist taxa were present on some higher islands characterised by areas with a height greater than 60 cm above the mean sea level. Notably, these rarely submerged soils hosted some uncommon halophilous species, as well as thermophilous taxa typical of Mediterranean habitats that were not present on the surrounding mainland. Overall, although the dredge islands possessed some topographical traits that differed significantly from those of the natural salt marsh, they proved to host the biotic communities typical of these latter habitats, as well as other saline soil specialists.

The Slender-billed Gull breeds with a scattered distribution on an extensive nesting area, ranging from India and Afghanistan in the East to the Iberian Peninsula in the West, including the Mediterranean and the Black Sea. A number of habitats are used for breeding, such as sand-spits and beaches along coasts and islands of land-locked seas, steppe lakes, but also brackish or freshwater lagoons near river deltas. Sea level rise dramatically affects coastal sites, thus being the greatest threat to the survival of many seabird species, including gulls. This note describes habitat selection, breeding success and causes of failure of Slender-billed Gulls during their colonisation of the northern Po Delta (NE Italy) during 2018 2022. Slender-billed Gulls colonised the northern Po Delta in 2018. Six colonies were found during the study period. Birds used both natural barrier islands and artificial dredge islands. Productivity in the first five years after the colonisation event was zero, mostly due to colony sites being flooded by high tides and storms. If Slender-billed Gulls will switch to nest in nearby fish farms, these could provide plenty of suitable breeding sites, safe from tidal flooding and with very low predation pressure, allowing sufficient productivity. At the moment, Slender-billed Gulls are unsuccessful in colonising the barrier islands of the Po Delta.

Man-made habitats provide suitable nesting, resting and feeding habitats for many birds at coastal sites. Despite intensive study outside Europe, very few data are available to date on the bird communities that exploit artificial intertidal sites along the European coasts. Between July 2009 and December 2010, 32 ornithological surveys were performed at six artificial intertidal sites in the lagoon of Venice (Italy). Overall, 101 species (with 23,399 birds) were observed, about a third of those occurring in the lagoon of Venice; 58 of these species were of conservation concern. Ten species comprised about 80 % of the total; bird abundance was the highest during the post-breeding migration and wintering period. Multivariate analysis identified similarity among sites, seasons and observed behaviours. Dredge islands were mostly used by waders as foraging sites, when surrounding tidal flats were still flooded. In winter the six dredged islands supported about 2 % of the dunlins Calidris alpina occurring in the whole lagoon of Venice and about 10 % of the grey plovers Pluvialis squatarola. Since the study sites comprised just the 6 % of the total dredge island area available in 2009–2010, the results indicate as large fractions of these shorebird populations might exploit the dredge island habitats for foraging. Among the newly created habitats, intertidal ponds and inner tidal flats were the most heavily used by birds, followed by dykes and mounds with ruderal vegetation. Maintenance of the habitat mosaic is a need for a conservation- based management of the dredge islands.

In 2022, highly pathogenic avian influenza (HPAI) A(H5N1) virus clade 2.3.4.4b became enzootic and caused mass mortality in Sandwich Tern Thalasseus sandvicensis and other seabird species across north-western Europe. We present data on the characteristics of the spread of the virus between and within breeding colonies and the number of dead adult Sandwich Terns recorded at breeding sites throughout north-western Europe. Within two months of the first reported mortalities, 20,531 adult Sandwich Terns were found dead, which is >17% of the total north-western European breeding population. This is probably an under-representation of total mortality, as many carcasses are likely to have gone unnoticed and unreported. Within affected colonies, almost all chicks died. After the peak of the outbreak, in a colony established by late breeders, 25.7% of tested adults showed immunity to HPAI subtype H5. Removal of carcasses was associated with lower levels of mortality at affected colonies. More research on the sources and modes of transmission, incubation times, effective containment, and immunity is urgently needed to combat this major threat for colonial seabirds.

We report on a decadal trend of accretionary dynamics in the wetlands of several northwestern Mediterranean deltas and a lagoon system, all of them with high rates of wetland loss. Wetland vertical accretion and surface elevation change were measured at 55 riverine, marine, and impounded sites in four coastal systems: the Ebro delta, Spain; the Rhône delta, France; and the Po delta and Venice Lagoon, Italy. Vertical accretion and elevation change ranged between 0 and 25 mm year⁻¹ and were strongly correlated. The highest rates of elevation gain occurred at riverine sites where vertical accretion was highest. We conclude that areas with high sediment input, mainly riverine, are the only ones likely to survive accelerated sea-level rise, especially if recent higher estimates of 1 m or more in the twenty-first century prove to be accurate. This is the first study where the importance of river input on wetland survival has been demonstrated at a decadal time scale over a broad geographical area.

In the last decade, the use of drones has proven to be the major innovation for studying various aspects of waterbird breeding biology, overcoming the environmental obstacles inherent in monitoring their breeding sites. The Squacco Heron represents an example of the aforementioned difficulties, since it nests in impenetrable reed beds and nearby bushes, trees and shrubs. The present work reports the results of drone assessment of nest counting and reproductive success of the Squacco Heron in a colony in the Po Delta (NE Italy). At the beginning of the breeding season, far more nests (46) were found using drones than by eye from the nearest embankment (12). After four weeks (estimated hatching period), only ten nests were relocated by drone, due to vegetation overgrowth. All relocated nests were placed directly either within reed beds or on lower branches of shrubs, but always without higher branches obstructing the view from above. Finally, in the fledging period, no nest was relocated on drone imagery, due to further vegetation growth. Only 27 juveniles were found by drone, mostly perching on the canopy, without any evidence of nest failure, suggesting a critical underestimation. In conclusion, drone use improves accuracy of counting nesting Squacco Herons, but fails to assess productivity.