O. Gy. Dely szerk.: Vertebrata Hungarica 20. (Budapest, 1981)

Horváth, L.: Communities of breeding birds in the peaty forest at Tabdi 69-74. o.

near to the scattered settlement of Tabdi. This latter part of the forest is greatly similar - as concerns the character of its landscape - to the alderwood marshes at Ocsa, in particular to Its section called the Turján! Forest. There are many lesser and larger clearings here and there too, the woods forming smaller islands or peninsula-like extensions into the surrounding turfy meadows. It results from this circumstance that some of the bird species breeding in the peaty meadows may be found also in the forest and, inversely, one or the other of the forest breeders nest in the nearby meadows, partly on the soil (i.g. Tree Pipit), partly in the isolated bushes (e.g. Turtle Dove) and trees (e.g. Wood Pigeon). It also belons to the characterization of the environment of the forest that the turfy meadow is not disturbed by man, except the time of mowing. This undisturbed condition has an effect not only on the bird life of the meadows but also on the enclosed parts of the forest. Apart from this direct and very essential influencing factor, the turfmoor also plays a role In the life of the silvicolous birds. Namely, at least one part of the bird life of the forest flows out of it, into its vicinity. The proximity of the meadows plays a very important role in the nourishing of one or the other species; on the other hand, elements also appear in the forest wich without presence of the turf moors, would not occur there at all. Consequently, the interdependence of bird life between the forest and the meadow is natural and must be taken into account.The peculiar arrangement of the nearly interwoven two types of country contributes to the development of the local breeding communities. This fact becomes indeed obvious when we compare it with forest areas of the very different type, but of a similar extension. Thus e.g. four breeding communities developed in the forest at Csévharaszt, and ten In the forest at Csornád, in contrast to the three under discussion (1/7, 1/8, i/ll). The reason for this is almost exclusively the environment of the forest area. Namely, the environment of the forest at Csévharaszt is turfy to a lesser degree only, and it is wiiolely absent from the surroundings of the Csornád Forest with its neighbouring, or rather intruding, ploughfieds. Beyond outlining the geography and soil conditions of the investigation area, some brief remarks should be made about the tree stands of the Tabdi Forest. Eighty per cent of the forest is composed of ash, there is a fair number of oaks and poplars, while alder is also numerous in the northwestern part of the wood; other kinds of trees occur in smaller numbers and only sporadically. However, the tree species do not primarily determine bird life here, but rather other circumstances. The most essential of them is that in certain parts of the forest - particularly in those of a drier substrate - there are very many bushes affording a rich and varied bird life. It is only favourable for the birds that they can find a fair number of old and tall trees sporadically all over the forest. In the followings I submit the results based on my observatons of the breeding communities In the Tabdi Forest made In the year 1979; comparisons made with my earlier data (1952-1956, 1977, 1978) collected in the peaty forest at Ocsa, of a similar character and also a part of the Kiskunság National Park. The first on order Is the Sylvia atricapilla breeding community with the serial number 1/7 in my basic work (HORVÁTH, 1956). The Roman numeral designates the type of country (forest), the Arabic one refers to the community of birds nesting together within the region. The breeding area according to my original definition is: "mixed, decidious forest - low, scattered, bushy undervegetation; in particular in the near of edges of wood, forest roads, pathes, lines and clearings". The latter restriction is founded on the marginal coenosis principle (Horváth, 1959). The permanent member of this category - with the Blackcap as the leader characterizing the breeding community - is the Song Thrust (Turdus philomelos). The subordinate members are, in the order of their frequency, as follows: Yellow Bunting (Emberiza citrinella)

, Turtle Dove (Strep- topelia turtur)

, Blackbird (Turdus merula), Tree Pipit (Anthus triviális

), Chiffchaff (Phylloscopus c

ollybita)

, Nightingale (Lusclnia megarhynchos)

, Marsh Tit (Parus palustris

), Robin (Erithacus ru be cula)

, Nightjar (Caprlmulgus europaeus) and Cuckoo (Cuculus canorus)

. The Tabdi Forest is not homogeneous as concerns undergrowth and soil moisture. On the drier portion mostly poplars and oaks grow; the bushy undergrowth is more abundant here. The Sylvia atricapilla breeding community is typical (i.e. complete) in only In such places, consequently all members of this community can be found only here. In parts of the forest with a moister substrate some of the subordinate members are absent (e.g. Nightjar, Tree Pipit, Blackbird). The Blackcap, the leading member of this community, lives here in a moderate number only (10 pairs). This phenomenon is in contrast with my earlier experiences in similar habitats, so In the alderwood marshes at Ocsa. Presumably the chemical plant protection contributes severely to the decrease in the numbers of the Blackcap in its entire distributional area.