Kivonat:

In eastern Hungary during the summer of 1997, 17 natural grasslands holding Corncrakes were analysed to establish their general biodiversity and to compare them with neighbouring grasslands that lacked calling Corncrakes. The diversity of plants and birds on a small scale was measured through a series of plot and point counts, while the diversity at site level was measured by standardised counts of species richness per site for plants, butterflies and birds. Sites with Corncrakes did hold more plant, butterfly and bird species than the control sites. The small scale of the point and plot counts meant that we could not explain this difference, which may indicate that the effect was mainly caused by a more heterogeneous habitat structure at the Corncrake sites. This is supported by the fact that the number of indicator species of hedgerows, bushes and isolated trees, but not of indicator species of open grasslands, was higher at the sites with Corncrakes. Tree Pipit Anthus trivialis, Common Cuckoo Cuculus canorus were associated with the Corncrake, (Corn Bunting Emberiza calandra tended to be associated with Corncrake) while (Eurasian) Skylark Alauda arvensis and Yellow Wagtail Motacilla flava tended to be commoner at the control sites. Corncrakes can be considered as a good umbrella species for the biodiversity of wet grassland habitats because the large and heterogeneous habitats suitable for this species also provide suitable niches for most other species of wet grasslands breeding in eastern Hungary.