Kopacki rit it is situated 14 km northeast of Osijek in an arch consisting of the Drava river at the site of influx into the Danube. This is a veritable treasury of nature with varied and interesting marsh, flood plain and swamp forest ecological systems. It is protected as a natural reserve with a special zoological reservation in an area of 17,730 hectares. In abundance of insects, frogs and fish - in other words, a proliferation of food in the water and surrounding it make for such an abundance of fowl there. This abundance pertains to the number of bird
species (267 species have been found, with 100 species also nesting there), as well as the overall multitude of fowl. Some of htem - the black stork and the great white crane - are quite rare in Europe. Our greatest eagle (orao stekavac) is especially prominent. The permanent water surface - Kopacko lake (around 2 sq. km) is the pivot of the zoological reserve. Areas where the water is more permanent are dominated by willows and poplars and in areas where floods transitory, there are more oaks and ash trees, and some alder. Living communities of our continental fauna abound.
They are represented by bucks, does, boars, foxes, wildcats, weasels, etc. Some species, especially deer, find the ecological conditions in this area especially favourable. Thus, organised hunting grounds with specific measures of cultivation have a centuries old tradition here. The zoological reserve is exempt from hunting and it is intended for unimpeded evolution and research into natural processes without human intervention. The fauna is characterised by great mobility, i.e. migration, because the entire life process is dependent on the influx of flood water and their recession.