A Debreceni Déri Múzeum Évkönyve 1986 (Debrecen, 1987)
Természettudomány - Juhász, Lajos–Bozsko, Szvetlana: The Ornithofauna of Debrecen II. Synecological Analysis
In the latter case the favourable vegetation structure and the presence of buildings creates extremely favourable ecological conditions for the birds, which is indicated by the outstandingly high values of A, H s and J. These exceed the indices of parks of similar category in Budapest (Sasvári, 1981) and West Berlin (Elvers, 1978). It seems that the choice of our plots may have been not quite fortunate, since the small park was the forepart of the large park of the University of Agriculture, which is separated from the rest of the park by the row of the university buildings and the inner motor road. It would be more correct to regard this biotope as part of the Park-City, which is, from the ornithological point of view, not identical with a traditional park. The H s and J values of the largest park (Great Forest, Cemetery) indicate, besides the highest species count, the most varied and a well separated fauna (Table 10, Fig. 2). However, the H s and J values are better for the bird community of the Cemetery than in the Great Forest which has a richer fauna with a higher number of species, for which no good explanation can be given. A special position is taken by outskirts, which is a mixture of a natural and an urban biotope. As an edge biotope it attracts to itself both the urban and the rarer, non-urban species. Its D species are still urban ones, the rare ones only give colour to the ornithocenose (See Table 9), but on the other hand, the H s , J and A values are here among the higest in the town (Fig. 2). Its D-identity is highly like with the green biotopes. In comparison with other towns, the species diversity means in Debrecen are relatively higher, at the same time, the means for number of species and abundance are roughly of identical order as e.g. in West-Berlin (Elvers, 1978) or Hamburg (Mulsow, 1982). Finally, omitting the migration period, which was discussed in detail in the foregoing, a few words must be said about the wintering communities of birds. In Debrecen the polarization of the ornithofauna is dimmed in winter, the sharp differences between the central and the green areas cease to exist. The birds concentrate themselves on the biotopes that can afford feed on a good level. In this period the dominance of some mass species is characteristic, both in the city and on the outskirts. The ED and D species of the winter are: Streptopelia decaocto, Corvus frufilegus, Columba livia domestica, Passer domesticus and montanus, in the invasional years also Bombycilla garrulus and Turdus pilaris, and further, Parus major, P. caeruleus, P. ater (Cm) as well as Carduelis spinus and C. cannabina (only in GF and IT). There is less scattering in the H s values (Table 10), however, the green areas possess a more varied and more evenly distributed ornithofauna even in winter. Taking the lead in the richness of species are the Great Forest and the small parks, the A value is suprisingly high in the latter (Fig. 2). The value of A considerably increases in the central city biotopes, too, as compared to the summer values, owing the appearance of mass species. 53
