Overview of the bird community historical data: bird assemblage multivariate analysis of the data collected from five mountain areas in the northern Croatia

摘要

Authors compared bird communities living in five mountain areas in the northern Croatia (Risnjak, Papuk, Medvednica. Ivanscica and Cesargrad mountain) using multivariate explorative techniques of qualitative and quantitative historical data. Similarity matrices were prepared based on Bray-Courtis similarity among samples. Non-metric multidimensional scaling (NMDS) and complete linkage clustering on qualitative and quantitative similarity matrix respectively were made. Principal component analysis (PCA) on quantitative data revealed bird species that contributed the most to the variability of samples. First three dimensions explain 75.2% of variance in samples (53.1%, 13.5% and 8.6% respectively) while the greatest loadings are caused by abundant species like Sylvia atricapilla, Erithacus rubecula, Turdus merula and Phylloscopus collybita. Non-metric multidimensional scaling revealed clear pattern in significant similarity among communities at low altitudes and at the same time-insignificant similarity among assemblages at different altitudes above the sea level (exception from the rule applies to the Papuk community at 600 m.a.s.l.). The clustering based on similarity matrix on qualitative data has shown clear separation among communities from different mountain areas. This study suggests that monitoring bird communities in the Croatian Mountains must be designed as repeated sampling of quantitative data through time.