Area requirements of passerine birds in the reed Archipelago of Lake Velence, Hungary

I studied the area requirement of reedbed breeding passerine birds on 109 reed islands in Lake Velence, Hungary, in the breeding seasons of 1993 and 1994. The size of the smallest occupied reed island for the observed 8 passerine bird species varied from 0.02 ha (Savi's Warbler Locustella luscinioides) to 4.14 ha (Bluethroat Luscinia svecica). Three species occupied reed islands which were 8-18 times larger than their territory sizes (Sedge Warbler Acrocephalus schoenobaenus, Moustached Warbler A. melanopogon, and Bluethroat), three species occurred on reed islands 4-4.5 times larger than territory sizes (Great Reed Warbler A. arundinaceus, Reed Warbler A. scirpaceus, and Reed Bunting Emberiza schoeniclus), and two species occurred on islands half the size of their territory sizes in continuous reedbeds (Bearded Tit Panurus biarmicus, Savi's Warbler). This may suggest that the latter two species can utilise groups of small patches within a territory. The incidence functions showed that the probability of occurrence of the Moustached Warbler and the Bluethroat was not 1 even on the largest reed islands (7-25.7 ha), while it was 1 for the other 6 species. The importance of landscape matrix type in determining minimum area requirements was demonstrated using data on the occurrence of bird species in reed marshes within an agricultural landscape in the Po Plain (Italy). In this landscape much larger minimum areas were found than at Lake Velence.