Abstract:

Bird community parameters were analysed in six stages of oak forest succession from brushwood to climax. Bird data were collected in the breeding season with the modified I.P.A. method, which gives density estimations for 100 m radius circles. Community diversity, expressed in relative density and rarefaction species number was greatest in the fourth stage of succession, in 61-80 year old forest stands. Open forest birds and hole-nesters reach their maximum densities here. A sharp difference was found between the community structure of the initial, open brushwood and the older, closed forest states. This pattern emerged both from comparisons of the whole community and of different ecological groups of birds based on primary feeding, nesting and migratory habits. Different speciation and adaptation mechanisms in the open and closed habitats are supposed to be responsible for this difference. No clear pattern emerged from the analysis of the degree of specialisation within families.