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

Abstract

Structure and dynamics of breeding bird assemblages of primaeval beech-fir forest in the rámková National Nature Reserve, the Malá Fatra Mts., Slovakia were studied during ten consecutive years 19972006. Bird abundances were estimated by the combined ver-sion of the mapping method in the 27.5 ha forest interior study plot. Determination of for-aging guild structure was done by a posteriori approach by a numerical analysis of ran-dom point observations of foraging birds. In total, 53 bird species were recorded as breed-ers 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 a mean difference in density among years of 33%. The highest fluctu-ations 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 Pearsons correlation coefficient of species densities showed no consistent grouping ac-cording 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 re-sults do not provide evidence for competition in the structuring of this bird assemblage, but instead support a pluralistic model of community functioning.