L. Forró szerk.: Miscellanea Zoologica Hungarica 7. 1992 (Budapest, 1992)

Andrikovics, S., Bankovics, A. , Csörgő, T. , Gere, G. , Sass, M.; Török, J.: Hydrozoological characters of a reconstructed wetland

been promoted by the fact that the water of the basin is overgrown with Polygonum amphibium, and it provides excellent nesting possibilities for the Whiskered Tern. The two species mentioned above may be examples of the different types of dispersal and immigration strategies of birds. Since 1988 there have been new changes in the avifauna. In 1990 Cormorants (Phalacrocorax carba) established a new colony in the water-reservoir. On May 30, 1990, there were 43 nests in the new colony, although 504 birds occured in the whole area. Some of the cormorants living in their traditional colonies, located in the strictly protected area (the former Kis-Balaton Nature Reserve), came to feed here from a distance of 6 km. The developing of this colony is rather slow. There were only 48 nets in the following year, on June 6,1991. The Mute Swan (Cygnus olor) shows a very dynamic immigration strategy. There were already three succesful breeding pairs in 1991. Pair of White-tailed Sea-Eagle (Haliaetus albicilla) settled in 1989. They built their nest in the canopy of an ash-tree, but they did not breed in 1989 and 1990. The Red-crested Pochard (Netta rufina) has a small, stable population here. There were 3 successful breeding families in 1991, but beside the 3 adult females with ducklings there were 8 adults without youngs. The very great water surface as well as the very rich food resources attract not just a mass of Cormorants but also different Herons, though till now they were only feeding here and were breeding in the neighbouring areas. Only two of them breed in the water-reservoir regularly, the Bittern (Botaurus stellaris), and the Little Bittern (Lxobrychus minutus), in very low numbers. The new water-reservoir has become an excellent resting and feeding site for a mass of migrant birds in the spring and autumn migration period. Summing up we can conclude that the fauna of the water basin is now in the state of rapid development and establishment although characteristic swampy vegetation has not been formed until now, therefore the polluting substances transported here by the water of the Zala River can be destroyed very slowly. Unfortunately the grasses bordering the original river-bed of the Zala are systematically removed and this decreases the ancient filtering effect of the swampy area. References Bankovics, A. (1991): Avifauna changes of the Kis-Balaton Reservoir area. - Miscnea zool hung. 6: 2330. Joó, O. & Lötz, Gy. (1980): A Zala folyó szerepe a Balaton eutrofizálódásában (The role of the Zala River in the eutrophication of Lake Balaton). - Vízügyi Közlem. 1980(2): 225-256. Keve, A. (1976): Beiträge zur Vogelwelt der Kis-Balaton I.-Aquila 82: 49-79. Keve, A. (1977): Data to the bird-fauna of Kis-Balaton II. -Aquila 83:191-226. Low, P., Sass, M. Csörgő, T & Török, J. (1989): Biochemical investigation of the Rana esculenta complex in the Kis-Balaton nature reserve, Hungary.-Acta Biol Hung 40:137-144. Vogel, P. & Chen, S. P. (1976): Genetic control of LDH isoenzymes in the Rana esculenta complex. Experientia 32: 304-307. Vbgel, P. & Chen, S. P. (1977): A further study of LDH isoenzymes in the Rana esculenta complex. Experientia 33: 1285-1287. Újhelyi, S. (1955a): Faunistical data of Central-European collections sampled by Hungarian collectors and kept in the Natural History Museum Budapest. -Folia enl hung. 8:17-44.