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Hybridization of the Mediterranean Gull Ichthyeatus melanocephalus in Poland

Zagalska-Neubauer Magdalena, Chodkiewicz Tomasz, Iciek Tomasz, Neubauer Grzegorz, Zieliński Piotr

Polish Journal of Ecology

2022

vol. 70, nr 4

175--184

Hybridization, the interbreeding of individuals from different taxa, is usually the result of contact between closely related species. It occurs when reproductive barriers between species are not fully developed during speciation. Gulls are a classic example of hybridization in birds. However, the group of so-called “small gulls” is poorly recognized in this context. Here, we summarised data on Mediterranean gulls Ichthyeatus melanocephalus hybridization documented in Poland for the 2006–2022 period. In the mid-20th century, this species began successfully colonising many European countries, and the first documented breeding pair of Mediterranean gull was recorded in Poland in 1981. The first documented cross-breeding between a male Mediterranean gull and a female black-headed gull Chroicocephalus ridibundus was recorded in Poland in 2006. Since then, a total of 25 interspecific pairs, between Mediterranean gulls and black-headed gull or common gull Larus canus, have been observed. Interspecific pairs with black-headed gull were the most numerous (76%). However, mixed pairs – formed by one of parental species and individual of the Mediterranean gull hybrid – were the most common pair category (N = 60). Neither pairs consisting of two hybrids individuals nor of Mediterranean gulls × common gull hybrids have been recorded in the colonies. The number of Mediterranean gulls fluctuated between 50 and 100 pairs during studied period. The number of interspecific breeding pairs remained constant over a 17-year period, one to three pairs per breeding season, while the number of mixed breeding pairs has increased over time and reached maximum 9 pairs per season. Overall, there is a clear increase in the proportion of mixed and interspecific broods in relation to the number of pairs consisting of two ‘pure’ Mediterranean gulls, such pairs approached 38% in 2019.

Co-occurrence of agile frog (Rana dalmatina Fitz. in Bonaparte) with common frog (Rana temporaria L.) in breeding sites in Southern Poland

Bartoń Kamil, Rafiński Jan

Polish Journal of Ecology

2006

Vol. 54, nr 1

151-157

A location (area 10 km^2) of the agile frog (Rana dalmatina Fitz. in Bonaparte) in a southwest part of the Sandomierz Valley (Southern Poland), was surveyed during 4 breeding seasons (1999-2002). Eighteen breeding sites of brown frogs were inspected for their characteristics, presence and numbers of egg-batches, and time of egg deposition. Breeding sites were typically temporary, small, and shallow waters (area 5-30 m^2, depth <50 cm). The agile frog was found to co-occur only with the common frog (Rana temporaria L.) in most of the sites. Based on the number of egg-batches, the agile frog was more numerous (total of 315 batches in year 2002) than the common frog (163). Over the four years of the study, there were no significant fluctuations in the numbers of eggs. The two species did not differ significantly in their choice of the habitats, except for the sites with low water pH, used predominantly by the agile frog. Habitat niche overlap was high (Pianka.s O = 0.86). In the acid pea In the acid peat bogs (water pH about 4.5) most of the eggs degenerated.