Gnezdilke Kopenskega dela Zadrževalnika Medvedce (SV Slovenija) In 2003, the breeding birds of terrestrial habitats at the partially sunken Medvedce reservoir were surveyed using the territory mapping method. In the area of 88 ha, 180 pairs belonging to 23 different bird species bred in that particular year. Compared with 1993, when the reservoir contained no water at all, 18 species ceased to breed, while 7 were new breeding birds. The main reasons for the changes in the area's avifauna were smaller surfaces of the reservoir's terrestrial part and the changed vegetation structure on the remaining land surfaces. Most of the species that ceased to breed at Medvedce reservoir, were the breeding birds of forest and densely-packed shrub stands. Among the new breeding birds, on the other hand, the species closely attached to reed and bulrush stands were predominant. Among the species of conservation concern, the Snipe Gallinago gallinago and the Meadow Pipit Anthus pratensis no longer bred there, while the Grasshopper Warbler Locustella naevia population was greatly reduced. The Tree Pipit Anthus trivialis, which had been the second commonest breeding bird at the reservoir in 1993, ceased to breed as well. The Reed Bunting Emberiza schoeniclus and Sedge Warbler Acrocephalus schoenobaenus populations were about the same as in 1993. Compared with this year, the Sedge Warbler density increased a great deal, reaching 4.7 territories / 10 ha. The same species' ecological density in pure bulrush and mixed bulrush and sedge stands reached 14.6 pairs / 10 ha and is salient on the Slovenian scale. The Grasshopper Warbler, Stonechat Saxicola rubicola, Linnet Carduelis cannabina and Red-backed Shrike Lanius collurio densities were high on the Central European scale. In 2003, breeding by three new bird species of conservation concern was established in the terrestrial part of Medvedce reservoir, i.e. the Yellow Wagtail Motacilla flava, Savi's Warbler Locustella luscinoides and Great Reed Warbler Acrocephalus arundinaceus. In 2004, the Spotted Crake Porzana porzana was recorded at the reservoir for the very first time during the breeding season.