The annual dynamics of the bird communities inhabiting the Morava river floodplain habitats:: reedbeds

This a first part of a study focused on quantitative analyses of annual changes in the composition of the bird communities inhabiting floodplain habitats of the Morava river riparian zone (Slovakia). Between 1992-1994 a three level methodological design was applied in the selected study area including a mapping method, line transect method and qualitative survey of the entire study area. Thirty species in total (21 breeders) were recorded in the reedbed habitat over the whole study area. The dominant position of non-sedentary species was observed for most of the year. During the non-breeding season this position refers to forest breeders attracted by food, especially Parus caeruleus overal the most dominant species in reedbeds during the non-breeding season. P. caeruleus and P. major, together with Emberiza schoeniclus and Panurus biarmicus (the only two reedbed sedentary breeders) are the only regularly occurring species in reedbeds outside the breeding season. They ale also accompanied with a group of communally night roosting species involving transmigrating Hirundinidae and year the round occurring Sturnus vulgaris. The latter is showing remarkable density fluctuation culminating during the premigration period by ca 10,000 roosting individuals. During the breeding season a pronounced dominance of migratory breeders (mainly Acrocephalus spp. and Locustella spp.) is apparent. Their spring influx increases habitat saturation with bird populations by up to 100% compared to the non-breeding season. In the first half of the summer, culmination of overall density is achieved by migration influx and fledging of young. The structural composition of the reedbed breeding community (total breeding density 118.7 pairs 10 ha(-1)) with low overall species number (8), nearly total absence of non-passerines and eudominant position of Acrocephalus schoenobaenus (30%), Emberiza schoeniclus (25%), Acrocephalus scirpaceus (23%) and Locustella luscinioides (11%), adequately reflects the structural features of most reedbeds in the study area with a prevailing terrestrial character without open water, with a dead stems layer and Carer understorey.