Piotr Zieliński, Tomasz Chodkiewicz, Monika Zielińska, Tomasz Iciek, Marcin Sidelnik, Jakub Szymczak, Dariusz Bukaciński, Monika Bukacińska, Antonina Rudenko, Grzegorz Neubauer, Arkadiusz Sikora
Ornis Polonica 2022, 63: 83–99
https://doi.org/10.12657/ornis.2022.2.1
Abstract: The analysed data were collected primarily within the Mediterranean Gull Census in the State Environmental Monitoring. There were 50–100 pairs breeding annually in Poland in 2006–2020. The Mediterranean Gull has nested in all regions of the country except in Podlasie, but the most numerous and stable colonies were present in south-western, central and north-eastern Poland. The most significant sites were located on dam reservoirs of anthropogenic origin, e.g. Mietków and Nysa reservoirs in Silesia, where c 15 and c 11 pairs bred annually over 15 years. Mediterranean Gull is scarcer and less abundant breeder on natural sites, e.g. on Ryn Lake in Masuria (7.6 pairs per year, on average, over 11 years of breeding) and in Kępa Wykowska nature reserve (Vistula river) – 3.5 pairs/year over 10 years. In 2018, the most numerous colony of 44 pairs was discovered in Bieńkowice gravel pit in Upper Silesia. In years 2007–2020, the abundance trend of the national population of Mediterranean Gull was moderately declining, and the average annual rate of decline amounted to –6.4% (λ = 0.936 ± 0.017 SE; 95% CI: 0.902–0.969; P < 0.05). In protected areas, the rate of decline was slower (–6.2% annually: λ = 0.938 ± 0.016 SE; 95% CI: 0.907–0.968; P < 0.05) than in remaining areas, where the population was declining significantly faster (–16.9% annually: λ = 0.831 ± 0.035 SE; 95% CI: 0.761–0.900; P < 0.05). Both the fluctuations and declines may be related to marked breeding dispersion (low philopatry) of the species: some individuals that have been ringed in Poland, move to colonies located closer to the wintering grounds in western Europe. This specific strategy makes the future of Mediterranean Gull as breeding species in the country uncertain and hard to predict.
Keywords: abundance decline, distribution, endangered species, Ichthyaetus melanocephalus, Mediterranean Gull, Monitoring of Birds of Poland
