Stefano Sponza

Ambush hunting is a highly effective tactic that enables close-range attacks by predators in disguise. While common across various animal groups, this foraging tactic is rare in seabirds. Here, we report an opportunistic observation suggesting that Mediterranean shags ( Gulosus aristotelis desmarestii ) might employ ambush tactics to seize small shoaling fish ( Atherina sp.). We observed one individual interacting repeatedly with particular submerged structures with the apparent intent of approaching their prey undetected. Building on a detailed analysis of our observation, we discuss alternative explanations for the observed behaviour including a potential multi-stage strategy entailing the active manipulation of the prey location. This preliminary evidence contributes to enrich shags’ foraging repertoire and highlights the need for further systematic research into the underwater behaviour of foot-propelled diving seabirds.

Summary: Bycatch, the incidental capture of non-target species in fishing gear, has been recognised as the most significant global conservation threat affecting seabird species. Geographically, bycatch rates vary widely, depending on local fishing efforts, environmental features, and seabird community composition. Regional and local research is essential due to the complexity of accurately extrapolating general conclusions regarding the impacts of bycatch. Existing European bycatch research predominantly focuses on northern regions, leaving a significant knowledge gap regarding bycatch in the Mediterranean Sea. This work presents findings of wintering diving seabirds as bycatch of small-scale fisheries in a coastal area of the northern Adriatic Sea, based on data collected between 2021 and 2023. Seabird distribution varied along the depth profile. The bathymetric range between 3 m and 5 m was the most exploited by fishermen. Bycatch of seabirds was confirmed in the study area, with five species recorded, i.e. Black-necked Grebe Podiceps nigricollis, Red-throated Loon Gavia stellata, Black-throated Loon Gavia arctica, Mediterranean Shag Gulosus aristotelis desmarestii, and Great Crested Grebe Podiceps cristatus. Our results suggest that bathymetry likely plays a strong influence on bycatch occurrence. Incidental captures were not widespread but appeared concentrated in the shallowest depths <5 m and the range <2.5 m was identified as particularly susceptible due to the low associated fishing effort and the majority of bycatch events recorded. We estimate that between 46 and 108 birds were incidentally captured during the research period. This study identifies key factors shaping the areas of bycatch vulnerability and risk, proposing a spatial–temporal mitigation framework within Natura 2000 sites and highlighting the value of local stakeholders’ engagement.

The Collared Pratincole Glareola pratincola has a large and fragmented breeding distribution in the Palearctic. In Italy it is an uncommon migrant breeder and the breeding sites are very patchily distributed and irregularly used, with most frequent occurrences in the N Adriatic, N Apulia, Campania, Sardinia and Sicily. We report a new breeding site for the species along the northern Adriatic coastline in the Marano and Grado Lagoon (Friuli Venezia Giulia region, NE Italy), which represents the first breeding evidence for the Friuli Venezia Giulia region.

The advantages derived from the use of Uncrewed Aerial Vehicles (UAVs) are well-established: they are cost-effective and easy to use. There are numerous environmental applications, particularly when monitoring contexts characterized by rapid morphological changes and high rates of sediment transport, such as coastal areas. In this paper, three different case studies of survey and monitoring with high resolution and accuracy obtained through the use of UAVs are presented; these concern transgressive coastal sites. Results allow for the definition and quantification of coastal landforms and processes, including: (i) The anatomy of a parabolic dune and the rate of landward migration that could interfere with a tourist settlement; (ii) The mode and timing of morphological recovery and realignment of a barrier island overwashed by storm surge episodes; and (iii) The potential flood risk of a progradational spit that is a nesting site of a species of migratory breeding birds of conservation concern. The results demonstrate and confirm that, through a good coupling of drone-sensed quality data and accurate topographic control, quantitative estimates that are useful in assessing the impacts of natural processes involving both human and natural assets can be obtained.

The Greater Flamingo Phoenicopterus roseus is known as an ecosystem engineer, rearranging sediment in peculiar bedforms as a consequence of its filter-feeding behaviour. In recent decades, the populations of the Greater Flamingo have notably increased, and now the species is one of the most abundant waterbirds in Mediterranean wetlands. Owing to its range expansion, it inhabits and exploits new and suitable foraging sites detectable by foraging structures left on the sediment. There are few images of the foraging morphologies in the literature, possibly due to their ephemeral nature and difficulty in detecting them. In this manuscript, we present a very detailed UAV (Unmanned Aerial Vehicle) image of an aggregate of pit foraging structures of Greater Flamingo discovered on a back-barrier washover fan in the Marano and Grado Lagoon (Northern Adriatic, Italy).

While beach erosion and sand loss are typically of great concern to the tourism industry, managing rapid morphological changes linked to large amounts of moving sediments is the challenge facing Grado, an important seaside resort in the northern Adriatic, Italy. The cause of the unusual management conflict is the presence of the Mula di Muggia Bank, a nearshore depositional system made up of relict and active migrating sandbanks extending up to 2 km seawards from the touristic beachfront. A reconstruction of the morpho-sedimentary evolution of the coastal system over a 200-year period was done using a large dataset which includes historical cartography, topographic maps, aerial photos and topo-bathymetric surveys. The results show the growth of a significant urban development aimed at creating a tourist destination by occupying the waterfront along fetch-limited coastal tracts with very shallow water and scarce hydrodynamics. Furthermore, a number of sandy dynamic landforms (longshore migrating bars, a bypass corridor, an ebb-tidal delta) and accumulation zones attest to a sediment excess which can be mostly attributed to the eastern river supplies. The progressive constant migration rate of 12.6 my⁻¹ allowed the bank to induce the expansion of the low-energy silty backbarrier environment, characterised by abundant seagrass meadows a short distance directly in front of the tourist beaches of Grado. As a result of historical analysis and more current observations, areas with diverse morphosedimentary features and with varying tourist/recreational, ecological, and conservation values have been identified. These can be considered as basic units for future accurate planning and re-evaluation of coastal management choices to balance environmental protection and tourist use. A soft coastal defence approach is proposed which includes either the preservation of specific environments or the proper use of excess sand for beach nourishment via periodic dredging or sediment bypassing.

Movements of Mediterranean Shags (Phalacrocorax aristotelis desmarestii, Payraudeau 1826) between Croatian breeding colonies and non-breeding areas such as the Gulf of Trieste increased consistently from the 1980s to become a migratory movement at the present time. In order to characterise the patterns of this migration and the behaviour of first-year Shags at their first migration, we analysed the recoveries of 812 birds that were colour-ringed at the most important Croatian breeding colonies in the northern Adriatic. Within a period of seven years, 568 ring-readings of 234 individual Shags were processed. Most sightings came from the Gulf of Trieste (43.0%) and the newly-discovered post-breeding area in Venice Lagoon (38.9%). Shags from the most distant colonies exploited mainly the Gulf of Trieste. The 48.3% of Shags sighted several times have been recorded in the same post-breeding area during subsequent years. This percentage increased to 93.4%, if we considered just the birds observed during successive years. Variations in the timing of migration within the post-breeding areas occurred and sustained the importance of the Slovenian coast during the return to breeding colonies. The ratio between first-year Shags and experienced Shags (immature and adults) was higher in Venice Lagoon and in general increased with the “novelty” of the site. A relevant portion of the Croatian breeding population moves to the northern Adriatic Sea after breeding. All the studied colonies concurred with this migration. We highlight a high fidelity to post-breeding sites, which reflects the quite sedentary “nature” of the species, and the role of first-year Shags in the discovery of new sites. We suggest that this migration is probably the later stage in a graded response to deterioration of the Shags’ feeding grounds within the breeding area.