Food source as a factor determining birds' exposure to hazardous organic pollutants and egg contamination

Alimentary exposure is the main factor determining halogenated organic compound pollution of wildlife, with birds’ eggs recognised as bioindicators of these contaminants and often used as a non-invasive monitoring tool. Comparisons of bird species from two aquatic environments, namely a marine coastal area (Gdansk Bay) and an inland reservoir (Włocławek Dam on the Vistula River), indicated significant differences in egg contamination. Herring gull eggs from Włocławek Dam had high concentrations of highly chlorinated dioxin (i.e. octachlorodibenzodioxin, which accounted for 37% of all polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo furans, PCDD/Fs). In contrast, eggs from terns feeding along the coastal area of the Southern Baltic contained high concentrations of lowly chlorinated furans (i.e. pentachlorodibezofuran, which accounted for 46 and 45% of all PCDD/Fs in eggs from the sandwich tern and common tern respectively). The congener patterns in terns’ eggs were similar to those reported previously for Baltic fish. Polychlorinated biphenyl congener 180 had the highest concentrations among the mono-ortho chlorinated biphenyls, whereas concentrations of non-dioxin-like chlorinated biphenyls were 10-fold higher than those of the other congeners analysed, but the congener pattern in eggs from both species (sandwich and common tern) was similar to that reported in other studies. Among the hexabromocyclododecane (HBCD) isomers, α-HBCD dominated in all eggs analysed (accounting for >97% of all HBCDs). The total HBCD concentration in gulls’ eggs from the inland reservoir was approximately half that in eggs from the common and sandwich terns (mean±s.d. 47.33±33.22v. 97.98±59.69 and 104.00±63.66ngg–1 lipid weight respectively).

Life History of Elegant/Sandwich tern hybrid

Life History of ringed bird -Elegant/Sandwich tern hybrid from researcher in France- Julien Gernigon

[Waders and seabirds (Charadriiformes) nesting along the north-eastern Adriatic coastline (Veneto and Friuli-Venezia Giulia) in 2008-2014: abundance, trends and major conservation issues]

[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]