Breeding bird assemblage dynamics of a primaeval temperate mixed forest in the Western Carpathians (Slovakia): Support for pluralistic community concept

Abstract

Structure and dynamics ofbreeding bird assemblages ofprimaeval beech-fir forest in the rámková National Nature Reserve, the Malá Fatra Mts., Slovakia were studied during ten consecutive years 1997-2006. Bird abundances were estimated by the combined version ofthe mapping method in the 27.5 ha forest interior study plot. Determination of foraging guild structure was done by a posteriori approach by a numerical analysis of random point observations of foraging birds. In total, 53 bird species were recorded as breeders in the study plot, averaging 39.0 species per year. Mean value of population variability coefficient (PV) of density of the 22 most numerous species was 0.33 + 0.14 SD (CV - 42.05%) indicating amean difference in density among years of33%. The highest fluctuations were detected in plant eaters (PV -0.47, N 3) followed by flycatchers (PV -0.44, N - 3), herb layer foragers (PV - 0.33, N -2), trunk foragers (PV - 0.33, N -2), foliage gleaners (PV -0.29, N -8) and litter foragers (PV -0.21, N 4). Cluster analysis of the Pearson's correlation coefficient of species densities showed no consistent grouping according to wintering areas or guild membership. Only seven of 26 simulations by binary null models (9 algorithms, 3 indices) on assemblage level indicated negative associations. None of 9 null model simulations of density assemblage matrix (3 algorithms, 3 indices) or null model analysis of foraging guilds showed negative species associations. The results do not provide evidence for competition in the structuring of this bird assemblage, but instead support a pluralistic model of community functioning.