INTERSPECIFIC COMPETITION IN RELATION TO HOMEOSTASIS

10-year study carried out in the Kampinos National Park shows that the total number of breeding pairs in multispecies bird communities is relatively stable. A particularly high stability in number was found for the group of species forming a competitive association. Analysis of numerical and spatial relationships in the association indicates that the tendency to maintain a stable number of breeding pairs has a character of homeostatic processes based on interspecific competition. The effect of association homeostasis on lower trophic levels is also discused. The present contribution is a preliminary analysis of the results obtained in long-term studies on the role of bird communities in forest ecosystems. Thus only basic concepts concerned with homeostatic processes in bird communities will be discussed here, without descrip tion of the methods applied. The analysis is based on the long-term population dynamics of birds inhabiting some habitats of the Kampinos National Park during the breeding seasons of 1964—1973. Generally, the Study was con ducted in an about 10-ha plot supporting a mosaic of the oak-pine forest (Pino-Quercetum), lime-oak-hornbeam forest (Tilio-Carpinetum), and alder foresit (Carici-elongatae-alnetum) (Tab. 1, stand PQ)- In addition, data collected in a damp pine forest (Vaccinio myrtilli-Pine-tum) are used for comparison (Tab. 1, stand YmP). It has been found that the total number of breeding birds in the community inhabiting stand PQ was relatively stable through ten successive seasons. For hole n esters! this stability was in fact maintained only during the period from 1964 through 1967, since in the following years their numbers were artificially increased as a result of supplying many nest boxesi; but the stability of the other part of the community was very high, the index of variability over ten years being 7.1% (Tab. 1)