Diurnal migration of birds in the Carpathian Mountains – characteristics, barrier effect and comparison with other regions in Poland

Abstract

Despite the development of technically advanced methods of studying bird migration, classical visual observations remain a source of valuable data allowing a broad analysis of the picture of diurnal migration at a given site. We employed visual observations to investigate the spatial and temporal pattern of diurnal migration of birds in the Polish part of the Carpathians. During autumns 2011-2013, 28 localities distributed over the area were surveyed by experienced observers, while 12 localities were researched in spring 2015. The data collected allowed the determination of passage intensity indices and the timing of migration for more than 100 species in autumn and about 70 species in spring. Mean passage intensity was more than 3 times higher in autumn than in spring, with the highest recorded in the first half of October and mid-March, respectively. Compared to autumn, the peak of diurnal migration was shifted to later hours in spring. The passage occurred primarily along the N-S axis, followed by the NE-SW axis. No consistent evidence of a barrier effect of the Carpathians – expressing as a reduction in passage intensity in intra-mountain locations or in higher elevated areas – has been detected in this study. The cluster analysis showed that the assemblage structure of migrants in the mountain regions located in the south of Poland (Carpathian Mts., Karkonosze Mts., Świętokrzyskie Mts.) were more similar to each other than to a region situated far to the north on the Baltic coast.