Abstract
The course of moulting in the first year of life of the Capercaillie (Tetrao urogallus) and Black Grouse (Lyrurus tetrix) was reconstructed by analysis and preparation of feathers of dead individuals. Following the down plumage that the chicks had since hatching, the so-called juvenile plumage is grown in the next 30 days, except for the slower-growing two outer primaries. There are almost no inter-sexual differences in this plumage, but it has a very characteristic pattern and allows the chicks to fly for a short distance. However, on average from day 17 of life in the Capercaillie and day 15.5 of life in the Black Grouse, the replacement of the juvenile to adult plumage starts by the moult of the first and the following primaries, so that at a certain time, the plumage consists of feathers of three different generations. The adult plumage is completed on average around the 110th day. A review of all published sources was carried out according to which the course of moulting of the two species is similar. A part of this study was completion of 37 feather collection sheets of juvenile and first-year adult plumage and museum skins which are attached as an electronic supplement to the paper and can be used to determine the feathers, e.g. found during field research. Some experience with collecting feathers during the field monitoring of the Capercaillie in the central Šumava/Bohemian Forest Mts. is presented.