Eduard Kletečki

Terrestrial snails (Mollusca: Gastropoda) of islands of Šolta, Drvenik veli and Drvenik mali (Croatia)

During the field work of our research into the terrestrial malacofauna of the eastern adriatic islands Šolta, Drvenik veli and Drvenik mali (Croatia) 36 snail species with shells were registered. That almost tripled the number of taxa recorded in the literature. We consider Lindholmiola corcyrensis (rossmässler, 1836) and Delima (Piceata) piceata (rossmässler, 1836), registered in the literature for Drvenik veli, non-existing for the researched area, as well as for Croatia. Of the recorded taxa we particularly refer to Odontocyclas kokeilii (rossmässler, 1837) with Šolta and Drvenik veli being its second i.e. third island localities in Croatia, and the endemic clausilid snail Delima (Semirugata) hiltrudis H. Nordsieck, 1969, also found on Šolta and so far known only from the island of Brač. The greatest number of species were found on the biggest island of Šolta, and the smallest island Drvenik mali had the lowest number of species, as expected. The values of the Whittaker index of biodiversity and of the maximum index of biodiversity increased according to size of island. The average number of taxa per site is the highest on the mid-sized island of Drvenik veli, which is a consequence of the diversity and good state of preservation of its habitats.

Daily Survival Rates of Eggs in Artificial Ground and Shrub Bird Nests on Small Adriatic Islands

Summary. Predation may cause important losses to the biodiversity of small islands. In this study we analysed the predation pressure on clutches of nesting birds in two islands of the Zadar Archipelago, Olib and Silba, which belong to an Important Bird Area (IBA) in Croatia. We paid special attention to introduced mammals: black rats Rattus rattus and feral domestic cats Felis silvestris catus. In May 2009, we carried out a study with artificial ground and bush nests. One quail egg and a plasticine egg of similar size were placed in each nest. On Olib, the daily survival rate of quail eggs in ground nests (0.92) was similar to that of nests located in shrubs (0.93), whereas on Silba the daily survival rates of quail eggs in ground (0.94) and shrub nests (0.86) were significantly different. We used the marks left on the plasticine eggs to identify nest predators. Many eggs in shrub nests (40% on Olib and 70% on Silba) were predated by hooded crows Corvus cornix. In ground nests on Olib, 43% of eggs were predated by hooded crows and small mammals, mainly black rats. On Silba Island, eggs in 33% of the ground nests were damaged by the above predators and also by the Montpellier snake Malpolon monspessulanus. Contrary to our expectations, feral cats were not found to be egg predators on either of the islands.