Acta Biol. Univ. Daugavp. 4 (2) 2004 ISSN 1407 - 8953 Introduction The ecology of macrozoobenthos of inland wa- ters is well known. Insufficiently examined is the problem of inhabiting specific microhabitats by macrozoobenthos, e.g. submerged parts of some birds` nests. It can be presumed that the nests provide invertebrates with good trophic condi- tions and a refuge from predators. The aim of the authors is to analyse preliminarily this problem on the example of bittern’s nests. The obtained results can point out a wilder phenomenon: only in Poland over 20 bird species from 7 families build nests, of which submerged parts can be suitable for inhabiting by macrozoobenthos: SUBMERGED PART OF THE NESTS OF EUROPEAN BITTERN BOTAURUS STELLARIS (L.) AS A SUBSTRATE FOR BENTHIC MACRO- INVERTEBRATES Paweł Buczyński, Ignacy Kitowski, Robert Rozwałka Buczyński P., Kitowski I., Rozwałka R. 2004. Submerged part of the nests of European bittern Botaurus stellaris (L.) as a substrate for benthic macroinvertebrates. Acta. Biol. Univ. Daugavp., 4 (2): 77 - 80. 12 taxa of macrozoobenthos were found in the submerged parts of bittern’s nests during preliminary studies in the area of pond complex in south-eastern Poland. The dominants were Dytiscidae and Hirudinea. The density of macrozoobenthos was high: 543 ind.·m -2 (462 ind.· m -3 ) on average. Almost the whole community was composed of predators. Habitat conditions of the fauna of nests and the forming of the fauna against other pond habitats are discussed. Key words: Botaurus stellaris, bird nest, macrozoobenthos, microhabitats, substrate Paweł Buczyński. Department of Zoology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland; e-mail: pbuczyns@biotop.umcs.lublin.pl Ignacy Kitowski. Department of Nature Conservation, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland; e-mail: kitowign@umcs.lublin.pl Robert Rozwałka. Department of Zoology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland; e-mail: rrozwalk@biotop.umcs.lublin.pl Podicipedidae, Ardeidae, Anatidae, Accipitridae, Rallidae, Laridae and Sternidae (Aulak 1989). Many of them are widely distributed (Tomiałojć, Stawarczyk 2003). Material and methods The studies were conducted in south-eastern Poland, in intensively used ponds in Samoklęski (51 o 27’ N, 22 o 26’ E). Five bittern’s nest – after the leaving of young birds – were collected on the 10th of July 2003; three of them were situated in water. The average area of a nest was 0,07 m 2 , volume – 0,113 m 3 (the emergent part: 0,085 m 3 ).