A Debreceni Déri Múzeum Évkönyve 1986 (Debrecen, 1987)

Természettudomány - Juhász, Lajos–Bozsko, Szvetlana: The Ornithofauna of Debrecen II. Synecological Analysis

wintering guests (Corvus frugilegus, Turdus pilaris, Bombycilla garrulus) leave this zone very soon. Taken as a whole, the fauna is unifacial with the hegemony and preponderance of some species. The nesting period shows the preponderance of species preferring high buildings. The abundance of Streptopelia decaocto decreases strikingly, although the dominance value remains nearly unchanged. Only the dominance of Passer domesticus is significant. On the other hand, it is general that the species occurring and nesting in the housing estates (12 species) populate the area with a sparse density. The relatively low number of nesting places give rise to a minimum number of individual birds (A=3.6 pairs/ha). The autumn wandering enhances the number of species up to 17, whereas the total number of individuals does not show any tendency of increase (3.2 pairs/ha). There appear typical wandering and wintering species (Corvus frugilegus, Parus major, P. caeruleus, P. ater, Phylloscopus collybita, Motacilla alba). These species, as variegating elements, enhance the value of the ornithofauna. In cold winters the number of species (19) and abundance value (4.5 pairs/ha) of the species is the highest and reaches the annual maximum. Qualitatively decivise are the winterning guests (Corvus frugilegus, Turdus pilaris, Bombycilla garrulus). Out of the birds staying in the town for the winter only, the summa D values of the species entering the housing estates is 41.47%, nearly the highest in the whole town. This fact shows the outstanding role of the housing estates in the migrating

—wandering periods. 4. Industrial areas (plot size: 18 hectares). In Debrecen only a few contiguous industrial zones can be found, however, these areas are to be regarded as separate biotopes. Here only a bird community consisting of a low number of species and individuals can be found. The extraordinary species stability of the area indicates, at the same time, a poverty in species (Table 4). In the spring period the appearance of 16 species can be registered. The low abundance values (2.3 pairs/ha) display a high dominance category, which is again a proof for the unsuitablity of the industrial zones as a biotope for the ornithofauna. It is worth mentioning that on this wide expanse of weed-overgrown uncultivated land the dominant species is Phasianius colchicus. There are only 6 breeding species in the industrial zone. The joint D value of Streptopelia decaocto, Passer domesticus and montanus, Phasianius colchicus, Galerida cristata, and Phoenicurus ochruros is 71.25%. This means that the nesting species are, at the same time, representatives of the zone. The autumn aspect of the bird communities is enriched, in addition to the settled mass species, with some wandering ones (Pica pica, Parus major, Troglodytes troglodytes). During the winters it is mainly the song-birds feeding on small seed that withdraw to the weedy areas of the industrial zone. At this time these show a higher total abundance (5.5 pairs/ha) than the mass species common everywhere, since the former come, in general, in the form of mixed or homogeneous flocks. It is Carduelis spinus that shows a significant number of individuals (5.5 pairs/10 ha) as compared to the others. 5. Garden city (size of plot: 22 hectares). As to its size it is the largest spot, it has a varied vegetation with rich facilities for feeding and nesting. These conditions result in a bird community of high ecological value. On the annual level 60 species can be demonstrated here, and taking the values for abundance and dominance into account, this indicates an association of high species diversity. Except for the high number of individuals of some common species, the abundance values of the other species do not show wide scattering (Table 5). The avifauna of the particular aspects also shows considerable diversity. In spring the number of species (40) and perhaps the number of individuals (7.3 pairs/ha) is maximum. The most numerous is Passer montanus, which is represented here by a larger 46