Tomiałojć L., Wesołowski T. 1996. Structure of a primaeval forest bird community during 1970s and 1990s (Białowieża National Park, Poland). Acta Ornithologica 31: 133-154.

Abstract. Results of mapping censuses carried out in plots situated in three types of old-growth stands (riverine, oak-hornbeam, coniferous) in 1990-1994 are presented and contrasted with data gathered in the same plots in 1970s (Tomiałojć et al. 1984). Community composition parameters: number of breeding species (72 versus 75), make-up of dominants, and overall assemblage similarity (Renkonen's index 76-87%) remained basically unchanged. Total density did not change in swampy stands but increased by 20-40% in oak-hornbeam and coniferous habitats. These increases were most pronounced in crown and bark insectivores guilds (what could be partially due to three year outbreak of Geometridae caterpillars in 1990s), in hole nesters and open nesters in tree crowns. All migratory groups but tropical migrants increased in numbers. The latter group remained numerically stable. Ground nester numbers did not change in dry habitats but they decreased in swampy places, parallel with the decreased hydration of this habitat in 1990s. In coniferous plots, growing number of gaps and expansion of deciduous trees, resulted in enrichment of breeding avifauna and increase in mean number of breeding species there.

Key words: bird community stability, primaeval forest, long-term study, species richness, community structure