Between 2001 and 2018 colonies of Gull-billed Tern were monitored in large wetland complexes of Veneto (lagoon of Venice and the Northern Po Delta) and Sardinia (western and southern) regions. Most of the colonies settled in man-made structures such as islets, levees, dams, located inside fish farms, fish ponds and salt pans. Laying took place around half May until early June (Veneto), with eggs occurring in the nests until half July (Sardinia). Colonies had 3-230 pairs, with several instances of isolated pairs; colonies were mono- or plurispecific, with other Charadriiformes. The number of eggs per clutch was 2.6±0.6 (N=111, 1 SD) in the Venice lagoon, 2.6±0.6 (N=182) in the Po delta, 2.3±0.70 (N=1007) in Sardinia; hatched eggs were 2.2±0.6 (N=111), 2.0±0.7 (N=182) and 1.7±0.67 (N=40) per nest, respectively. The most important cause of breeding failure was due to flooding of nesting sites, due to the rapid increase of water levels inside fish farms and salt pans. During the 2001-2018 years, the Gull-billed Tern nested regularly in Sardinia, whereas in the Po Delta the first nesting occurred in 2001 and in the lagoon of Venice in 2008. The whole population ranged between 34 and 417 pairs until 2017 (223.6±113.4, N=17), with a sudden increase up to almost 1,000 pairs in 2018; the overall trend is of strong increase (p<0.01), with an annual rate of 10.5%.

[In 2008-2014 wader and seabird nesting pairs were censused along the 220-km long coastline of the NE Adriatic Sea, in the Veneto and Friuli-Venezia Giulia regions (NE Italy). Fourteen species were regularly breeding, with an annual mean of 20,610 pairs (±1553, 1 SD). The most abundant species was the Yellow-legged Gull (about 13,400 pairs on average, 65% of the whole population of the study area), followed by the Common Tern (1670 pairs, 8.1%) and Common Redshank (1525 pairs, 7.4%). The whole population of waders and seabirds increased with an annual rate, estimated with the TRIM software, of +0.8%, with a greater increase (+4.3%) if the Yellow-legged Gull was not included. Twelve species were stable or increasing; only the yellow-legged gull (-1%) and the common redshank (-2.4%) were decreasing. The populations of several species exceed 10% of those estimated for the whole of Italy; those of the Eurasian Oystercatcher, Common Redshank and Sandwich Tern are among the most important in the whole Mediterranean. On average, about 8860 pairs (43%) nest in the Venice lagoon, 6,400 pairs (31%) in the Po Delta, 5100 pairs (25%) in the Friuli-Venezia Giulia lagoons. Among nesting habitats, semi-natural (such as the fish farms) and man-made sites (dredge islands) make each year about 70% of the nesting pairs. Saltmarsh islets host large numbers of Common Redshank and Sandwich Tern, while along the beach zone the only abundant species are the Yellow-legged Gull and the Eurasian Oystercatcher. The major conservation threats observed in the study area were the erosion of littoral islands, the uncontrolled occurrence of sunbathers along the beaches, the vegetation overgrowth at dredge islands, the increasing frequency of saltmarsh submersion by high tides, the strong fluctuations of water levels inside the fish farms.] [Article in Italian]

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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 (Ardeola ralloides) 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.

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