From 1999 to 2003, 83 captive-reared juvenile Capercaillies Tetrao urogallus were released in the Harz Mountains National Park (Lower Saxony), fitted with VHF transmitters and tracked regularly. The aim of the study was to find out whether the released Capercaillies use a diet similar to wild birds. The background here is knowledge about nutritionally impaired captive-reared grouse due to highly - digestible and nutrientrich commercial poultry food provided in aviaries, leading to deficits in survival in the wild. 109 droppings were collected and examined microscopically for food fragments. Plant remains were determined using a reference collection of food plants and based on generic cellular structures. The main nutritional components found in droppings collected between October and February of birds released in autumn were spruce Picea abies (34%), bilberry Vaccinium myrtillus (26%) and herbs (20%). The diet of birds released in spring was dominated by spruce (56%) and grass (20%). The proportion of conifers in autumn and winter was lower than expected in comparison to wild Capercaillies which feed almost exclusively on needles in winter. Considering the three release dates in autumn (1999, 2002 and 2003) separately revealed that the proportion of spruce was low between December and February ranging from 18% to 64%. Diet change towards conifer needles, as occurring in wild birds in autumn, could only be proved on the basis of individual samples and was delayed into February. Favourable climatic conditions allowing the birds to forage on the ground until well into the winter season, as well as nutritonal deficits such as a lower digestive capacity may have caused this shift. Since the main goal of such conservation action has to be releasing survivable individuals, future release projects of grouse have to fulfil some basics. Among them is a feeding routine which fulfils the nutritional requirements for successful preparation for the wild. If this requirement is not met the further use of captive-reared grouse for release projects is not longer recommended.