L. Forró szerk.: Miscellanea Zoologica Hungarica 10. 1995 (Budapest, 1995)

Báldi, A., Zágon, A.; Bankovics, A.: Status of the avifauna in the Szigetköz riparian area: an ornithological evaluation for nature conservation

included 207 species from the avifauna of the Szigetköz. The Barnacle Goose (Branta leucopsis) were not included in their analysis, because it is very rare in Hungary. The mean of the biological scores for all the bird species is 12.79 and 12.13 for those occurring in the Szigetköz. The average for the scores of the status of the Hungarian population is 6.22 for all species, and 6.21 for those observed in the Szigetköz region. Discussion The large riparian area of Szigetköz is suffering drastic changes due to the dam construction works of the Gabcikovo hydroelectric power-station. The decrease of the watertable is serious, estimated to be several meters below the pre-construction level. In addition, the forestry harvests all the remaining forest and plantations. Therefore we may state that the Szigetköz is an essentially modified landscape. Considering that there is only a single habitat type, the riparian habitat, with several plantation and forest types, the 208 species (58%) seems to be a very high representation of the Hungarian avifauna. Below we argue, that the Szigetköz has several other important ornithological features, which are worth to consider. The Szigetköz harbour interesting aviafauna from a biogeographical point of view. The area of the two vicariant Corvus species (or subspecies, according to different systematics), the Carrion Crow (C. corone) and the Hooded Crow (C. cornix) overlap in this region. Several montan species occur in this plain area, like the Dunnock (Prunella modularis), Willow Tit (Parus montanus) and Treecreeper (Certhia familiáris). The Icterine Warbler (Hippolais icterina) has a more dense population than in other Hungarian areas. The Olivaceous Warbler (H. pallida) expanded its range in the last years mainly along rivers. It have bred already in the Szigetköz. The extensive meanders, dead-branches and rivers provide good wintering area for many waterfowl and their raptors, like the White-tailed Eagle (Haliaetus albicilla). That is why the Szigetköz is proposed to be a Wetland of International Importance (i.e. a Ramsar site). The status of the most valuable species indicate that the riparian habitats and river branches are very important both for breeding (15) and for migrating (16) species. There are 6 species from the 32, which were rare in the area, but their typical habitats are not the riparian ones. The average of the scores for the Szigetköz species set from the ranking system of Báldi et al. (1995) showed that the rank of the species was not skewed, may be as a consequence of the large species number. They listed the most threatened 34 bird species for Hungary. From that list 23 (68%) species were observed in the Szigetköz. Since this is the latest and most comprehensive ranking system for vertebrates in Hungary, the fact, that more than two-third of the threatened bird species of the country occur in the Szigetköz reflects the high value of the area, and the need of more active nature conservation. Knowing the possible dramatic changes in the area we may expect that many of the most valuable species are the most vulnerable as well. These are species which (1) do not tolerate human disturbance, like the raptors, the Great Bustard (Otis tarda) and Black Stork (Ciconia nigra); (2) require mature forests, like the Black Woodpecker (Dryocopos martius) and Middle Spotted Woodpecker (Dendrocopos medius); and (3) mainly those species requiring wetlands or riparian habitats like the Great White Egret (Casmerodius albus), Corncrake (Crex crex), Bluethroat (Luscinia svecica), etc. Therefore recent human activities in the Szigetköz and in the whole region highly threaten the most fragile species. Unless well-designed and financed